Special Alert: Permafrost-related Abstracts, 2021

USPA LogoThis Special Issue contains 232 abstracts related to the topic of permafrost as listed in the program of the Fall Meeting of the AGU that took place in New Orleans, LA, Dec. 13-17, 2021.


To view a list of PMAs follow the button below.

View all PMAs


The PMA program was made possible by the following sponsors in 2021:

AFI Logo GWS Logo CS Logo





2022057067 Abe, Takahiro (Mie University, Tsu, Japan) and Iijima, Yoshihiro. Interannual and seasonal surface displacement near the settlement in Churapcha, eastern Siberia, revealed by ALOS-2 [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Thermokarst is an irreversible phenomenon with terrain changes induced by ground ice melting in ice-rich permafrost and has been widely observed in eastern Siberia. In the Lena-Aldan interfluve in eastern Siberia, thermokarst development has been remarkably undergoing in these 30 years. Thermokarst-induced surface deformation can cause destruction of infrastructure and change in water budget and ecosystems, which impacts the lives of neighbors. Churapcha is one of the residential areas in the interfluve where thermokarst development has been notably observed. Although a previous study estimated the surface subsidence since 1990 by UAV, the amount of surface subsidence in the entire city is still uncertain. In order to predict where and how thermokarst progresses and minimize the impact on local people due to permafrost thawing, it is essential to quantify spatial variation and rate of surface subsidence due to thermokarst development. L-band SAR interferometry by ALOS-2 reveals a significant surface subsidence trend of 1-2 cm/yr in two arable lands (T1 and T2) in the north and a grassland (T3) in the south of the Churapcha settlement between 2015 and 2020. Numerous high-centered polygons in the places by WorldView images indicates that thermokarst has been developing. Changes in land use in this area shows that T1 and T2 were cultivated from forest to arable land between 1945 and 2009. Loss of vegetation due to the cultivation has enhanced the impact of solar radiation on permafrost, and thermokarst has progressed compared to the surroundings. On the other hand, no inter-annual subsidence and even seasonal subsidence/uplift were detected in arable land A, located a few kilometers east and at the same elevation as T1 and T2. A possible interpretation is that there is a different underground ice and soil structure in A compared to T1 and T2, which is a condition where seasonal thaw subsidence and frost heaving are unlikely to occur.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/881713

2022059948 Abolt, Charles (Los Alamos National Laboratory, Los Alamos, NM); Nitzbon, Jan; Langer, Moritz and Atchley, Adam L. Reducing uncertainty in simulations of thaw in ice-rich permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H42B-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Understanding rates of permafrost thaw across the Arctic is key to predicting how essential ecosystem functions, such as carbon exchange between the soil and atmosphere, will change in a warming climate. In ice-rich permafrost, predictions of future thaw rates are particularly difficult, as they must account for complex thermo-hydrologic and geomorphological interactions. One particularly challenging process to represent is the formation of thermokarst pools, or meter-scale ponds which develop in subsidence pits atop melting bodies of ground ice embedded in the permafrost. The presence of these pools fundamentally alters the surface energy balance, with the net result of accelerating thaw. Here we explored uncertainties in modeling these physical dynamics by simulating the effects of thermokarst pools on the soil thermal and hydrologic regimes using two state-of-the-art codes: Amanzi-ATS, a physics-rich simulator tailored to capture fine-scale surface and subsurface processes in cold environments, and GryoGrid, a land surface model configured to simulate permafrost thaw over broad (i.e., continental) spatial scales while accounting for sub-pixel resolution processes in heterogeneous landscapes. The results revealed that, despite significant structural differences between the modeling paradigms, the two codes often predict similar fluxes of energy and water between thermokarst pools and the surrounding environment. Among the most sensitive parameters in the simulations were the thermal properties of the winter snowpack, which strongly impacted vertical heat exchange between the ground, surface water, and atmosphere. Overall this study suggests that: 1) representation of small (i.e., meter) scale landscape heterogeneities is essential to understanding permafrost thaw dynamics, 2) despite necessary reductions to the underlying soil physics, land surface models are viable tools for simulating complex interactions between thermokarst pools and permafrost, and 3) circumpolar data regarding snow pack thickness, thermal conductivity, and temporal dynamics will be key to reducing uncertainty in global projections of permafrost thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/865695

2022059945 Akbarpour, Shaghayegh (University of Waterloo, Waterloo, ON, Canada) and Craig, James R. Multinomial simulation of land cover evolution in discontinuous permafrost zones of Northwest Territories [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H35M-1179, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Land cover evolution is one of the major responses of nature to global warming. Each terrestrial ecosystem is susceptible to specific driving forces of change originating from climate warming. In the lowland discontinuous permafrost regions of the Taiga Plains, permafrost thaw is the main cause of land cover change. Investigations of the discontinuous permafrost regions demonstrate that the distribution of the dominant land types (permafrost plateaus, fens, and isolated bogs) and their hydrological properties has been greatly affected by thawing.Here, we developed a machine learning-based model to estimate the evolution of the main hydrologically-important land covers in the discontinuous permafrost region. The multinomial time series land cover model (TSLCM) is able to simulate historical landcover transitions, simulate spatial patterns of change, and replicate the long-term evolution of landcover at the Scotty Creek Research Station (SCRS), NWT, and similar landscapes. Our input data includes a set of spatio-temporal variables: the estimated land surface temperature (LST), the distance to landcover interfaces, time horizon (from 0 to 38 years), time-accumulated land surface temperature, and classified landcover maps from 1970-2008. The process of implementing TSLCM starts with training a generative model by employing a random forest (RF) and a Multiple Linear Regression (MLR) method; it improves the performance of the TSLM in extrapolating time series change by boosting the initial data-set. Then, We used a MLR and an extreme gradient boosting (XGBoost) model to simulate landcover change.Compared to the MLR method, the RF method showed better results in replicating historical land cover change; our main concern was that the model did not perform well in generating plausible future scenarios. To overcome this problem, we added new data instances to the initial data-set by combining the predicted land cover change and the observational dataset. The final outputs of MRL and XGBoost trained on boosted data-set confirm that Ensemble Learning (EL) models are weak learners in forecasting time series change and capturing the correlation between spatial and temporal variables. The predicted time series land cover maps to the year 2100 suggest that permafrost plateaus are rapidly transforming to fens.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/975481

2022059955 Akbarpour, Shaghayegh (University of Waterloo, Waterloo, ON, Canada) and Craig, James R. Semantic segmentation of isolated wetland in discontinuous permafrost regions of the Northwest Territories using deep convolutional neural networks [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract IN44A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost thaw is modifying the distribution of dominant land covers in discontinuous permafrost regions. To better understand effects of thaw-induced changes on properties of watershed and wetlands, we first need a method to discriminate isolated and connected wetlands from other types of lands from remotely sensed imagery of discontinuous permafrost regions. High resolution imagery provide comprehensive information of any geographic region; and combination of remote sensing and deep learning methods has improved the performance of models in image processing. The biggest challenge for classifying land covers in the Northwest Territories (NWT) is lack of access to high resolution imagery, and the challenges associated with prepossessing the data for discriminating wetlands from forest-covered regions.Here, we applied a semantic segmentation neural model and a multi-layer perceptron (MLP) method for classification of isolated wetlands. The input data-set includes WorldView-2 Satellite imagery covering Scotty Creek Research Station in NWT of Canada, and the image is labeled with three types of lands: wetlands, lake, and forested area. We focused on two important objectives to improve upon other implemented methods for classification of wetlands in discontinuous permafrost regions: using only RGB images and use of an image segmentation method to accelerate the automatic classification of land cover. The model is tested on 10 study sites in the NWT. The semantic segmentation method reached an accuracy of 93 percent in classification of water, permafrost plateaus, and wetland; the accuracy of MLP model for detecting isolated bogs from other types of wetlands is 98 percent. Our model generates classified maps that discriminate between isolated wetlands (bogs), connected wetlands (fens and connected bogs), and forested area which can be used in hydrological analyses for delineating the secondary (bog contributing areas) and primary (fen contributing areas) contributing areas.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/979565

2022057010 Alexander, Heather Dawn (Auburn University, Auburn, AL); Paulson, Alison; DeMarco, Jennie; Loranty, Michael M.; Mack, Michelle C.; Hewitt, Rebecca E.; Lichstein, Jeremy W.; McEwan, Ryan W.; Robinson, Seth; Davydov, Sergei P.; Spektor, Valentin and Zimov, Nikita. Mechanisms of post-fire larch forest recovery in far northeastern Siberia [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B55A-1200, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Severe wildfires across high-latitude larch (Larix spp.) forests of Siberia have the potential to alter carbon cycling both directly through increased emissions and indirectly through changes in seed availability and environmental conditions that affect patterns of forest recovery. To better understand the factors affecting larch recruitment after fire, we used a combination of observational and experimental approaches at two locations in northeastern Siberia (Yakutsk and Cherskiy, Russia) that differed in regional climate, fire history, and prevalence of deciduous hardwoods. Near Yakutsk, where hardwoods co-occur with larch, we characterized tree regeneration composition and abundance in 25 plots distributed across a mixed-severity fire (323 km2) that burned in 2002. Near Cherskiy, where larch is the primary tree species, we quantified larch recruit density within five early-successional (2 plots. We sowed seeds (400 m-2) on these plots and quantified seedling establishment during the subsequent growing season. Across studies, we found seed availability (e.g., proximity to nearby live trees, absence of seed predators) to be the primary filter impacting post-fire larch recruitment, with environmental conditions (e.g., resource availability and residual SOL depth) being secondary filters. These findings suggest that larch recruitment likely benefits from heterogeneous, moderate severity fires that maintain some live trees as seed sources while also reducing competition and maintaining safe sites for seeds. However, large, high-severity fires that kill seed trees and/or create groundlayer conditions that increase seed visibility while providing places for predators to hide could cause forests to transition to grasslands, shrublands, or deciduous hardwood forests, with implications for carbon cycling, permafrost stability, and energy/water fluxes, and thus, fire-vegetation-climate feedbacks.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/942550

2022059977 Anderson, Lesleigh (U. S. Geological Survey, Denver, CO); Jones, Miriam; Berkelhammer, Max B.; Jones, Benjamin M. and Stephani, Eva. Holocene pore-ice water isotope variations from permafrost peat soils in southern Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract PP15B-0905, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In south-central Alaska, where modern mean annual temperatures are ~2°C, permafrost continues to exist, albeit sporadically and primarily in ecosystem-protected areas such as spruce plateaus within peatlands. The permafrost history of the region is unknown, and this study of a 600-cm permafrost core obtained from a spruce plateau in the Kenai Peninsula investigates downcore variations in the isotopic ratio of the pore-ice water. Oxygen and hydrogen isotope ratio of the pore water were measured in 2-cm intervals for comparison with macrofossil analyses and cryostratigraphic investigations on a radiocarbon-based age model. Results indicate that the onset of peat accumulation, with >90% organic matter, and syngenetic permafrost aggradation, with water content by weight >95%, had begun by ~11,000 BP (calibrated with respect to 1950) and continued uninterrupted until ~9,600 BP. Comparison of the oxygen and hydrogen isotope ratios during this interval indicates equilibrium freezing conditions and shifting inverse trends in deuterium excess (d-excess) with d18O and d2H values. After 9,600 BP, an abrupt shift to mineral sediments occurred, possibly unconformably. The ~100 cm of mineral sediments persisted until ~4,500 BP, and the d18O and d2H values of the ~60% water content are higher than in the early Holocene, reflect disequilibrium freezing conditions, and have relatively low d-excess. Above the mineral horizon, a resumption of peat accumulation is characterized by steadily declining d18O and d2H values and rising d-excess, coincident with macrofossil trends that suggest permafrost re-aggradation after ~3,000 BP. Some aspects of the isotope trends may prove to be accounted for by vertical movement of unfrozen water within permafrost soils in response to seasonal pressure gradients. However, similar millennial scale trends in other regional d18O records, including a nearby peat cellulose core, suggest preservation of a paleohydrologic and paleoclimatic signal.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/900802

2022059932 Antwi-Agyei, Jefferson (University of Maryland, Applied Research Laboratory for Intelligence and Security, College Park, MD); Hernandez, Alexia and Koehn, Jason. Approach to estimate current and future destabilization risk to energy facilities on permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55J-0531, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost is permanently frozen ground that covers over 10% of the Earth's surface. Many northern regions have extensive infrastructure built on this hard, frozen ground. When permafrost thaws, the ground becomes a softer mix of soil and water, which can cause degradation and damage to critical infrastructure. Permafrost thaw has substantial economic, strategic, and environmental implications. While thawing permafrost due to climate change will affect energy infrastructure in many countries, this work focuses on Russia's current and planned arctic energy infrastructure. To quantify Russian energy infrastructure locations on permafrost, geospatial data was collected and mapped. Specifically, our analysis focuses on Russian gas and oil terminals and power plants. First, we determined the types of permafrost extents (e.g., continuous, discontinuous, sporadic, and isolated) on which each energy facility lies. Next, to evaluate the infrastructure hazard potential of permafrost thaw, we leveraged an existing analysis by [Karjalainen et al., 2019] in which data on ground conditions were weighted and aggregated to generate low, medium, or high hazard classifications under various greenhouse gas trajectories. For the time frame 2041-2060 and assuming greenhouse gas trajectories consistent with RCP 4.5, most facilities were found to be located in moderate and high hazard zones. A similar analysis was conducted for the years 2060-2081 under various climate conditions. Next, we generated supplemental analysis to define similar hazard classifications under current climatic conditions. The future climate scenario findings are compared with current conditions to identify potential variations in hazard zones, which could heighten infrastructure destabilization. Findings are applied to a targeted case study of the Yamal Peninsula to assess implications for Russia in the areas of energy capacity, foreign investment and supply chains, and future infrastructure construction projects.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/896034

2022059983 Baker, Jonathan (Xi'an Jiaotong University, China); Li Tingyong; Wang Tao; Zhang Jian; Wu Yao; Li, Hong-Chun; Blyakharchuk, Tatiana; Yu, Tsai-Luen; Shen, Chuan-Chou; Cheng, Hai; Kong Xinggong; Xie Wenli and Edwards, R. Lawrence. Early Holocene permafrost retreat in West Siberia amplified by reorganization of westerly circulation [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract PP43B-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Warming of Eurasian permafrost regions is of critical concern for water resources, ecological balance, and future carbon fluxes. Rapid permafrost degradation and peatland expansion during the Early Holocene may provide an analog to anthropogenic warming, but the disparity in regional dynamics precludes a direct comparison of the two intervals. Here we present a novel 230Th-dated, multiproxy speleothem record with subdecadal sampling resolution from Kyok-Tash Cave, located along the modern permafrost margin in the northern Altai Mountains, southwestern Siberia. Stalagmite K4 (11.4-8.9 ka B2K) indicates the absence of stable permafrost within three centuries of the Younger Dryas termination. From 11.4-10.4 ka, speleothem d18O is uniquely antiphased between the Altai and Ural ranges, suggesting a reorganization of westerly circulation that led to warmer and wetter winters over West Siberia and Altai, relative to the zonally adjacent regions of Northern Eurasia. The positive d18O excursion in K4 over this interval coincides with evidence of peak permafrost degradation and peatland expansion in West Siberia, consistent with the interpreted climate anomaly. We emphasize the sensitivity of modern permafrost in Eurasia to feedbacks in the ocean-cryosphere system, which are projected to alter circulation regimes over the continent.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/849997

2022057019 Balazs, Matthew S. (University of Alaska Fairbanks, Alaska Coastal Geoscience Lab, Fairbanks, AK); Maio, Chris; Jones, Benjamin M.; Farquharson, Louise Melanie and Kasper, Jeremy. Alaska coastal center; matchmakers for coastal research and communities [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C25B-0835, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Alaska has roughly half of the US coastline, yet remains the most poorly mapped and studied terrestrial/marine interface in our Nation. These areas are experiencing extreme environmental variability due to climate change and nearly 150 indigenous communities are impacted by environmental hazards associated with coastal flooding, erosion, and permafrost degradation. Magnifying these environmental issues is a disconnect between agency and university scientists, engineering firms, industry, and local tribal governments. Too often it is discovered there has been a duplication of effort after the fact due to not knowing what others are actively working on. To address these complex challenges, we seek to establish a coastal research center at the University of Alaska Fairbanks to provide the framework to foster synergy leading to actionable research and solutions for Arctic coastlines and the people that live and work there. The vision of the center is to build relationships across disciplinary and cultural boundaries to develop and act on shared research goals that address the impacts of coastal hazards and environmental changes. The center will partner with coastal communities to address co-identified priorities such as identifying the pace and economic costs of coastal hazards, risk to infrastructure, socioeconomic costs of mitigation, and environmental conditions impacting their communities. The center will serve as a central knowledge repository with information of the scientific and engineering work that is being done in the state. This investment in research infrastructure will improve communication and help inform future work by identifying shared goals between coastal communities and stakeholders working in the Arctic. The interdisciplinary and inter-agency nature of the center requires sound direction and sufficient levels of autonomy for all parties to properly manage their own projects. We investigate governance models used by the NSF AccelNet, PerCSNet, University of the Arctic, and others to help guide the future direction and organizational structure of the Alaska coastal center. Our initial plans for shared governance and network to network collaboration are given. We invite feedback and advice from anyone who wants to share the success or challenges they have had in their own organizations.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/1002088

2022055984 Baltzer, Jennifer Lynn (Wilfrid Laurier University, Department of Biology, Waterloo, ON, Canada); Sniderhan, Anastasia; Standen, Katherine; Dearborn, Katherine and Ogden, Emily. A shifting foundation; changes in Canada's northern forests in response to permafrost thaw [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24D-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

High latitude amplification of warming is altering permafrost conditions throughout the circumpolar north. The implications of this for forest composition, structure, and dynamics are poorly understood even though much of the boreal biome occurs in permafrost zones. Climate warming and permafrost thaw may positively influence boreal forest productivity through belowground mechanisms including: (a) release of temperature constraints on biogeochemical cycling and nutrient availability or plant belowground productivity and function as soils warm, permafrost thaws, and the active (seasonally thawed) layer deepens, which can enhance tree growth; and (b) release of previously inaccessible soil resources during permafrost thaw which can enhance primary productivity if trees can access these novel resource pools. Conversely, a deepening active layer can act to limit access to soil moisture for shallow rooted species, resulting in ecological drought and reduced physiological function and growth. Variability in tree responses to permafrost thaw may underlie some of the ambiguity in remotely sensed measures of boreal forest productivity over recent decades. In this presentation, we will synthesize some recent efforts to understand the impacts of permafrost thaw on northern boreal forests. Results will span scales of biological organization from the leaf to the landscape; such a multi-scale approach is critical for evaluating the mechanisms driving spatial variability in boreal forest response to ongoing permafrost thaw. We find differences in species physiological and growth responses to ongoing permafrost thaw and show that this can be linked to forest demographic processes and remotely sensed measures of ecosystem productivity. These results will be discussed in the context of the functioning of high latitude boreal forests.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/858769

2022059962 Barker, Amanda J. (U. S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK); Sullivan, Taylor D.; Barbato, Robyn; McInturff, Grace; Saari, Stephanie; Douglas, Thomas A.; Gallaher, Shawn Glenn and Smith, Joseph P. Using geophysics to understand seasonal controls on metal transport in Arctic watersheds [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS11A-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

To understand landscape-scale watershed dynamics in arctic regimes, it is critical to investigate abiotic and biotic interactions in the transition zone, where the active layer meets the permafrost. Geophysical techniques sensitive to the liquid and solid phases of water, like electrical resistivity tomography (ERT), ground-penetrating radar (GPR), and nuclear magnetic resonance (NMR), can inform sampling locations and identify zones of potentially higher biogeochemical reactivity in permafrost watersheds. Permafrost, which is a considerable component of arctic soils, contains a unique interface at the transition zone characterized by a sharp redox gradient and a phase change from liquid water to ice. The biogeochemical composition and environmental conditions at this interface influence reactivity--i.e., as permafrost thaws, a higher proportion of interfacial water may be present, disrupting the localized microenvironment. Associated changes in the amount of unfrozen water present will likely affect redox environment, microbial activity and diversity, speciation, water density, conductivity, and soil wettability. Imnavait Creek is a tundra stream on the North Slope of Alaska where we collected soil and water samples across seasonal thaw and coupled GPR and ERT to characterize watershed active layer thickness and identify permafrost extent across the stream, respectively. Our work there shows the permafrost-active layer interface is a reducing zone highly susceptible to mass flushing of redox active elements (e.g. iron; Fe) if thawed. ERT results showed low resistivity volumes adjacent to and beneath Imnavait Creek indicative of a thaw bulb, which may contribute to late season metal mobilization, though the magnitude and timing remains unclear. As permafrost degradation accelerates, there will be rapid changes to the first 1-2 meters of the soil with potentially significant chemical and biological changes occurring near the permafrost-active layer interface. Employing non-invasive geophysical techniques to sense moisture distribution enabled more effective mapping of this critical interface and allowed for approximating microscale biogeochemical reactivity and metal transport at the watershed scale.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/970542

2022057005 Barker, Patrick (University of Manchester, Manchester, United Kingdom); Allen, Grant; Pitt, Joseph Robert; Bauguitte, Stéphane; Pasternak, Dominika; Cliff, Samuel; France, James L.; Fisher, Rebecca; Lee, James D.; Bower, Keith and Nisbet, Euan G. Net methane and carbon dioxide exchange from European Arctic wetlands in summer 2019; airborne quantification and bottom-up intercomparison [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B51C-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic wetlands and surrounding ecosystems are understood to be both a significant source of methane (CH4) and a sink of carbon dioxide (CO2) during summer months. Arctic wetlands contribute an estimated 7-16 Tg CH4 year-1 to the global methane budget, whereas the terrestrial Arctic represents an average CO2 sink of -0.13 Pg CO2 year-1. Surface exchange of methane and CO2 in the Arctic is also highly sensitive to climate feedbacks due to the presence of Arctic amplification of global warming. Arctic mean air temperatures have increased at more than twice the rate of the global average, with current arctic temperature growth over 1.5°C higher than the 1971-2000 global average temperature growth with further warming predicted for the future. Higher temperature may result in enhanced microbial methanogenesis in wetland ecosystems. Furthermore, thawing of permafrost as a result of increasing temperature may result in an increase in arctic wetland extent as well as enabling the release of organic carbon from the estimated ~1700 Pg of stored soil organic carbon in arctic permafrost. It is therefore clear that methane emissions from high-latitude wetlands may become increasingly important over time due to their high sensitivity to climate change. However, precise quantification of the Arctic methane source and CO2 sink remains poorly characterised. The Methane Observations and Yearly Assessment (MOYA)-Arctic field campaign was conducted from 29 July 2019 to 2 August 2019 based in Kiruna, Sweden. This field campaign used in situ aircraft measurements to quantify emissions of CH4 and other trace gases from northern Swedish and Finnish (Fennoscandian) wetlands (66-69°N, 22-28°E) during the summer period. This work presents aircraft mass balance flux estimates for wetland CH4 emission and biospheric carbon dioxide uptake during one of the survey flights carried out during the MOYA-Arctic campaign and compares with previous similar aircraft studies in the region. Additionally, this study compares the fluxes obtained via aircraft mass balance with fluxes from Global Carbon Project (GCP) wetland process models, where both the magnitude and spatial distribution of CH4 fluxes are compared with the aircraft results.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/830054

2022055949 Barry, Kevin Robert (Colorado State University, Fort Collins, CO); Hill, Thomas Christopher James; Moore, Kathryn A.; Kreidenweis, Sonia M.; DeMott, Paul J. and Creamean, Jessie. Tracking ice nucleating particles from permafrost to the atmosphere through thermokarst lake and oceanic transport [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A52B-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost in the Arctic (ground that remains frozen for more than 2 years) is thawing rapidly as global temperatures continue to rise. Thawing permafrost can have several potential effects on climate, including release of greenhouse gases into the atmosphere. This study will consider the much lesser-studied impact of melting permafrost on clouds. Aerosols, and more specifically ice nucleating particles (INPs) influence Arctic mixed-phase clouds (e.g., phase, albedo, precipitation, lifetime) since they are necessary for the initiation of primary ice formation at temperatures warmer than -38 °C. Recently, we have discovered that permafrost can serve as a large reservoir of INPs, and that they are primarily of biological and organic origin. However, what happens to the INPs as melted permafrost soils enter thermokarst lakes and rivers, and subsequently the ocean or atmosphere, is unknown.Here, we present controlled laboratory experiments as a part of ARCSPIN (ARCtic Study of Permafrost Ice Nucleation), which includes both laboratory and field efforts to assess permafrost biota and INP emissions through freshwater and marine environments. To test potential permafrost INP emissions, a small quantity of two Alaskan permafrost cores, dating back 1,000 and 30,000 years, were placed into a tank with artificial freshwater and aerosolized with a simulated rain shower. INP concentrations in the water and air, as well as the aerosol size distributions, were measured for 25 days for each core. Additionally, the salinity and water temperatures were changed midway through each incubation to simulate transport into brackish and oceanic conditions along coastal regions of the Arctic Ocean. Water and aerosol filter collections were also used to track bacterial community composition through 16S rRNA sequencing. The older permafrost core was found to be a larger source of INPs in the water as well as a more efficient source of lake spray INPs. INPs from both cores showed remarkable stability (both in the water and aerosol) with time and changes in salinity. These results will help inform the field component of ARCSPIN taking place in Utqiagvik, Alaska in September 2021 and the larger goal of improving climate model representation of Arctic mixed-phase clouds.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/1001668

2022057043 Bartsch, Annett (b.geos, Division of Research and Development, Korneuburg, Austria); Pointner, Georg; Widhalm, Barbara; Nitze, Ingmar; Grosse, Guido; Lantuit, Hugues and Vieira, Goncalo. Monitoring the human footprint across the Arctic coastal region in the context of climate change impact assessment [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Infrastructure and anthropogenic impacts are expanding across the Arctic. A consistent record of human impact is required in order to quantify the changes and to assess climate change impacts on the communities. We derived a first panarctic satellite-based record of expanding infrastructure and anthropogenic impacts along all permafrost affected coasts (100 km buffer) within the H2020 project Nunataryuk based on Sentinel-1/2 satellite imagery. C-band synthetic aperture radar and multi-spectral information is combined through a machine learning framework. Depending on region, we identified up to 50% more information (human presence) than in OpenStreetMap. The combination with satellite records on vegetation change (specifically NDVI from Landsat since 2000) allowed quantification of recent expansion of infrastructure. Most of the expanded human presence occurred in Russia related predominantly to oil/gas industry. The majority of areas with human presence will be subject to thaw by mid-21st century based on ground temperature trends derived from the ESA CCI+ Permafrost time series (1997-2019). Of specific concern in this context are also settlements located directly at permafrost affected coasts. An efficient erosion rate monitoring scheme needs to be developed and combined with settlement records in order to assess the risk for local communities and infrastructure. Relevant progress in the framework of the ESA EO4PAC project will be discussed.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/927974

2022057009 Beckebanze, Lutz (Universität Hamburg, Center for Earth System Research, Hamburg, Germany); Rehder, Zoé; Holl, David; Mirbach, Charlotta; Wille, Christian and Kutzbach, Lars. Small waterbodies reduce the carbon sink strength of a polygonal tundra landscape in eastern Siberia [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B54E-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic permafrost landscapes historically functioned as a global carbon sink. These landscapes are very heterogeneous, and the omnipresent waterbodies are a carbon source within them. Yet, only a few studies focus on the impact of these waterbodies on the landscape carbon budget. We compare carbon dioxide and methane fluxes from small waterbodies to fluxes from the surrounding tundra using eddy covariance measurements from a tower located between a large pond and semi-terrestrial vegetated tundra.When taking the open-water areas of small waterbodies into account, the carbon dioxide sink strength of the landscape was reduced by 11%. While open-water methane emissions were similar to the tundra emissions, some parts of the studied pond's shoreline exhibited much higher emissions, underlining the high spatial variability of methane emissions. We conclude that gas fluxes from small waterbodies can contribute significantly to the carbon budget of arctic tundra landscapes. Consequently, changes in arctic hydrology and the concomitant changes in the waterbody distribution may substantially impact the overall carbon budget of the Arctic.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/859386

2022057017 Beddrich, Jonas (Technical University of Munich, Munich, Germany); Gupta, Shubhangi and Wohlmuth, Barbara. Alpine permafrost modeling; the influence of complex topography and lateral fluxes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C22C-06, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Alpine permafrost is highly vulnerable and sensitive to climate trends. Assessment of the impact of global warming requires multi-physics models which can adequately capture thermal exchanges, the freezing and thawing of soil mass, and subsurface flow processes. Most recent permafrost models rely on the simplifying assumption that there are no lateral fluxes and utilize one-dimensional numerical schemes to reduce the computational complexity. While these approaches yield reliable results for Arctic and sub-Arctic permafrost, in alpine regions, such simplifications can lead to significant errors due to the high spatial variability of the terrain. Here, we present our physical-based permafrost model, which can handle the lateral fluxes and the complex topography of mountainous areas. We study the influence of these factors on the distribution of permafrost and the active layer thickness in the case of the elevation profiles of the Zugspitze (DE) and the Matterhorn (CH). Our results indicate that the active layer thickness varies significantly between slopes and corresponding peaks. On uneven terrains, the permafrost distribution is highly irregular despite similar elevation and surface temperature. This effect is even stronger for the active layer. Moreover, the surrounding conditions influence the depths of the two layers, even at level plateaus. Therefore, both, the distribution of permafrost and the active layer, are heavily influenced by the lateral fluxes caused by spatial variations of the mountain profiles. Furthermore, it is not possible to derive their state solely based on the surface temperature and elevation without consideration of the surrounding conditions. These outcomes are highly relevant as they offer new insights into prevailing model assumptions and highlight the need for more specialized approaches for alpine regions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/936198

2022056010 Behnke, Megan Irene (Florida State University, Tallahassee, FL); Tank, Suzanne; McClelland, James W.; Holmes, Robert Max; Raymond, Peter A.; Eglinton, Timothy I.; Haghipour, Negar and Spencer, Robert G. Delineating particulate organic matter sources in the major Arctic rivers; the importance of contemporary autochthony [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B44A-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Climate change is warming the Arctic rapidly, leading to significant changes in permafrost extent and stability with ramifications for carbon cycling. Destabilized soil carbon can enter large Arctic rivers, which are important organic matter integrators as they represent all landscape processes and features in their watersheds, and provide a comprehensive summary of the state of the Arctic ecosystem. The ongoing debate about the quantity of permafrost carbon currently being released to rivers as organic matter masks an even more fundamental issue: where does Arctic riverine organic matter come from, and how may its sources change with a changing climate? Here we use a comprehensive suite of endmembers and tracers to provide a complete assessment of the controls on particulate organic matter (POM) sources and fluxes in Arctic rivers and draw conclusions about temporal and spatial dynamics of endmember contributions. We use eight years (2012-2019) of POM data sampled every two months from the six largest Arctic rivers (the Ob', Yenisey, Lena, Kolyma, Yukon, and Mackenzie; Arctic Great Rivers Observatory) to create river-specific three-tracer mixing models using carbon to nitrogen ratio, d13C, and D14C of POM. The models use pan-Arctic endmembers representing autochthonous and allochthonous POM sources (recent terrestrial production, aquatic biomass, shallow soil, and deep soil endmembers) as well as river specific sources (yedoma and petrogenic carbon). To improve the rigor of our analyses, we further propose an alternative to the traditional division between "active layer" and "permafrost" for discussions of pan-Arctic soil organic carbon. We report fluxes of specific POM endmember sources by year and season, explore the idea that previously overlooked endmember sources such as aquatic biomass may form a critical component of the POM pool, and discuss how changing POM sources can play a role in ecosystem function in a changing Arctic.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/957948

2022056007 Bennett, Kathryn A. (Université de Montréal, Département de Géographie, Montreal, QC, Canada); Varner, Ruth K.; Perryman, Clarice R.; Kuhn, McKenzie Ann; Burke, Sophia A.; Hoyt, Alison; Yanez, Cindy Cristina; Oh, Youmi; Erazo, Natalia; Heffernan, Liam; Olefeldt, David; Sonnentag, Oliver and Czimczik, Claudia I. A synthesis of in-situ emissions and dissolved sub-surface d13C-CH4d13C-CO2, and dD-CH4 from northern wetlands, lakes, and seasonally-inundated ecosystems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Wetlands, lakes, and seasonally-inundated ecosystems in northern latitudes store large amounts of carbon (C) and are globally important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere. However, estimates of these greenhouse gas (GHG) fluxes and their sources remain uncertain and a major challenge for understanding the permafrost C feedback. The improved understanding of stable isotopes emitted from northern aquatic sources will help partition global and regional GHG emissions in atmospheric inversion studies. Stable isotopes of CH4 (d13C and dD) can also establish dominant methanogenic pathways and identify shifts due to climate forcing. In an effort to identify isotopic signatures of major GHG emitting landscapes at high latitudes, we synthesized measurements from in-situ studies of d13C-CH4d13C-CO2, and dD-CH4 from Arctic (>60°N) and boreal ecosystems (>50°N). Our preliminary results from 22 studies, across the entire study region, show mean isotopic signatures of -60.5±9.2 ppm (n = 362) and -61.8±10.1 ppm (n = 231) for d13C-CH4 emissions and subsurface measurements, respectively, and means of -12.2±9.8 ppm (n = 22) and -12.0±7.9 ppm (n = 184) for d13C-CO2 emissions and subsurface measurements, respectively. However, signatures of d13C vary significantly between wetland, lake, and tundra land cover classes (p Mean dD-CH4 from emissions and subsurface measurements are -356±35 ppm (n = 72) and -334±47 ppm (n = 108) respectively. Studies including dD-CH4 data are limited, preventing preliminary conclusions regarding differences between land cover classes. We will present an expanded analysis using land cover classifications from the Boreal-Arctic Wetland and Lake Database. Constraining the ranges of d13C-CH4d13C-CO2, and dD-CH4 from northern landscapes will improve our understanding of their contributions to the global C cycle and inform modeling of future global climate projections. This synthesis can be integrated into warming scenarios that project how hydrologic and land cover changes driven by rising temperatures, permafrost thaw, and sea level will impact the global CH4 and CO2 budgets. This study will also be used to identify landscapes in transition, identify gaps to drive research priorities and predict shifts in systems acting as sinks to sources of GHG as permafrost thaws.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/950220

2022059937 Benz, Susanne (Dalhousie University, Centre for Water Resources Studies, Halifax, NS, Canada) and Kurylyk, Barret. Global patterns in shallow groundwater warming due to climate change [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H22C-02, sketch map, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Shallow aquifers provide large freshwater reservoirs, critical habitats, and sustainable and renewable energy resources. Changes in shallow aquifer thermal regimes have far reaching implications, including changing groundwater quality, altered geothermal potential, and accelerated permafrost thaw. Groundwater temperatures also impact surface water bodies and their complex, temperature-sensitive ecosystems. However, we presently know very little about global variations in shallow subsurface thermal regimes and even less about groundwater warming patterns due to climate change. Here we characterize large-scale groundwater temperature patterns in space and project temporal changes at the global scale by using existing parsimonious analytical solutions to the conduction-advection equation forced with surface temperature projections from the ERA5-Land climate reanalysis data. We use high-resolution, global estimates of sand, silt, and clay content of the shallow subsurface to estimate local thermal diffusivity and parameterize our solution. We present our results as a Google Earth Engine app allowing any user to estimate and visualizes temperature depth profiles down to 50 m at any location for the past two decades. Through this analysis we are able to model groundwater warming beginning in 2020 and find that temperatures at 30 m depth increase on average by 0.18±0.17°C. However, warming is very heterogeneous, with some areas experiencing cooling up to 0.2°C (e.g. in Northern China, South India and parts of Western Canada) and areas where temperatures increased by more than 0.6°C (e.g. in Northern and Eastern Africa, Central Asia and parts of the western United States).By combining our analysis with the CMIP5 Representative Concentration Pathways scenarios we will further be able to project a suite of future temperature changes. This enables us to identify high risk areas for permafrost thaw as well as 'hot spots' for emerging groundwater quality issues due a decline in oxygen saturation and pH associated with changing temperatures.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/849689

2022059913 Bergstedt, Helena (University of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, AK); Jones, Benjamin M.; Kanevskiy, Mikhail Z.; Parsekian, Andy; Rangel, Rodrigo Correa and Hinkel, Kenneth M. High-salinity liquid water as a source of uncertainty in bedfast lake ice mapping on the Arctic Coastal Plain in northern Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract G34A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic permafrost landscapes are characterized by numerous shallow lakes. Lakes play an important role in the Arctic ecosystem as crucial areas of wildlife habitat and drivers of landscape change. Depending in part on lake depth and other characteristics, lakes differ in their winter ice conditions. >50% lakes on the Arctic Coastal Plain in northern Alaska develop bedfast ice, with ice freezing to the bottom of the lakebed during the winter. Synthetic Aperture Radar (SAR) data (e.g. ERS-1/ERS-2, RADARSAT, ENVISAT ASAR) has previously been used to distinguish between bedfast and floating ice lakes on a regional and circumpolar scale, creating a possibility to quantify different winter ice conditions on a large spatial scale and how they might annually to year and in response to climate change. High salinity liquid water present below ice has been found to be a source of uncertainty in bedfast lake ice mapping efforts, however, leading to misclassification of floating lake ice as bedfast lake ice. High-salinity water can be caused by ocean water intrusions through storm surges for near coastal lakes, as well as through saline soils that are a relic of past high sea level stands. As ice forms throughout the winter, salts in the water are excluded which also amplifies salinity below the ice. To further investigate the possible magnitude of errors introduced into bedfast lake ice data sets, we compare long term records of ice thickness and salinity measurements on the Arctic Coastal Plain of northern Alaska with multi-source SAR records (ERS, RADARSAT, Sentinel-1). In addition, we aim to better understand the changes in salinity and ice conditions for multiple lakes in the region including their possible interactions with surrounding lakes, river channels and the impact of possible storm surges introducing highly saline ocean water. Identification of the misclassification of floating ice lakes as bedfast ice lakes due to the presence of brackish to saline water below the ice has implications for permafrost thaw, ecosystems, the potential presence of extremophiles, and winter overland travel route planning and safety.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/975607

2022059947 Bergstrom, Anna (Boise State University, Boise, ID); Wright, Anna; Singley, Joel G. and Gooseff, Michael N. What is a watershed? Shifting perspectives from long term research in the McMurdo dry valleys, Antarctica [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H41B-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

One of the first things hydrologists do at a study site is define the watershed, which is often determined topographically. However, in the McMurdo Dry Valleys (MDVs) of Antarctica, it is not so simple. This polar desert landscape is made up of glaciers, bare soils, lakes and stream channels. It receives little precipitation, all in the form of snow. Most snow sublimates, meaning there is little to no snowmelt runoff generated across the landscape, and the dominant source of streamflow is from meltwater draining off the surface of glaciers. Hillslopes are underlain by permafrost and thought to be completely disconnected from streams. This leaves us asking where is the watershed boundary and how do we define it? The delineation of the watershed can affect how we interpret a range of processes that we infer from stream discharge and chemistry including weathering, nutrient cycling, and response to a changing climate. For example, we have observed almost ubiquitous chemostasis across weathering products and nutrients. Do we attribute this to entirely in-channel processing or should we consider solute sources from elsewhere? Over 30 years of research, MDV watersheds have been defined by only the active stream channel, expanded to include the ablation zone of the glacier, and more recently broadened even further to the entire topographically delineated watershed. In water limited systems, from polar to mid-latitude deserts, the entire topographic watershed may not always contribute water, solutes or nutrients to the stream (except during extreme precipitation events). Or, certain areas may contribute only at discrete times or locations. Here, we explore how the process of interest informs the definition of the watershed and the implications for how we interpret findings and direct future research efforts.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/802976

2022056019 Berns, Erin C. (Oak Ridge National Laboratory, Oak Ridge, TN); O'Meara, Teri; Herndon, Elizabeth; Sulman, Benjamin N.; Gu, Baohua and Graham, David E. Linking water and oxygen availability to biogeochemical redox cycling and carbon release in Arctic soils [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1755, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Across the Arctic, the seasonally thawed soil active layer is deepening as permafrost continues to degrade. Formation of thermokarst features - collapsed soil resulting from permafrost thaw - can form conduits for water and dissolved organic carbon (DOC), leading to biogeochemical environments that contrast adjacent upland soils that are still underlain by permafrost. Hydrological transitions due to thermokarst formation can promote changes in oxygen availability, microbial soil organic carbon (SOC) decomposition, and biogeochemical redox cycling, ultimately impacting the magnitude and proportion of carbon dioxide (CO2) and methane (CH4) released from Arctic soils. As these changes become more frequent and widespread, it is increasingly important to understand the controls on SOC decomposition in these dynamic environments and effectively model their interconnected hydrobiogeochemial processes. This study focuses on how soil water saturation and drainage impact oxygen availability, microbial utilization of alternative terminal electron acceptors (e.g., Fe(III)), biogeochemical cycling, and CO2 and CH4 fluxes from upland and thermokarst soils. These processes were investigated in two column experiments with soils obtained from a thermokarst site near Council, Alaska. Soils were packed into an insulated column with a controlled thermal gradient and instrumented with optical oxygen sensors, volumetric water content sensors, and MicroRhizon samplers. Water was drained from the soil columns and deionized water was reintroduced at the top of the column as precipitation in a series of saturation and drainage cycles. Throughout the experiments, CO2 and CH4 were measured in the column headspace. Porewater samples were used to measure pH and dissolved species (DOC, iron, major anions, and organic acids) with depth through the soil profile. Upland and thermokarst soils were compared in terms of carbon release and relative importance of SOC respiration, iron reduction/oxidation, and methanogenesis. An improved understanding of dynamic water and oxygen availability on redox cycling and carbon release in Arctic soils could support development of process-based reactive transport and SOC degradation models that are being coupled to terrestrial components of Earth system models.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/965985

2022059920 Blahut, Nina (Joint Global Change Research Institute, College Park, MD); Evans, Meredydd; Kholod, Nazar and Wilson, Cathy Jean. Linking climate change and human systems; a case study of Arctic pipelines [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC52C-03, sketch map, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

This case study estimates the potential economic risk from permafrost thaw on oil and gas pipelines in the Russian Arctic as part of a larger effort to better understand complex interactions between human and natural systems in the Arctic. Pan-Arctic simulations of permafrost thaw-depth from the Community Land Model version 4.5 and ground ice characteristics were used to generate thaw-induced ground subsidence projections over the period 2020 to 2040 with a quantification of uncertainty. Engineering analysis and expert input were used to estimate the magnitude of ground subsidence likely to cause significant pipeline damage. Then, Russian oil and gas transmission pipeline networks were overlaid on the ground subsidence projections in ArcGIS to identify pipelines vulnerable to damage from permafrost thaw. Recent pipeline construction costs were used to estimate the total replacement costs for at-risk pipelines under several thaw scenarios. The results indicate that permafrost thaw poses a major threat to pipeline infrastructure, especially gas pipelines, in the Russian Arctic. Over the twenty-year study period, total replacement costs for oil and gas pipelines were estimated at $110 billion in 2020 USD. The study also includes an uncertainty analysis on the range of possible replacement cost estimates due to combined uncertainty from permafrost projections, pipelines' subsidence tolerance, and Arctic construction costs. Reduced economic viability of pipelines under climate change could trigger major shifts in the Russian oil and gas industry, which would have impacts on global markets, emissions, and geopolitics.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/817070

2022057049 Bristol, Emily M. (University of Texas at Austin, Austin, TX); Connolly, Craig T.; Behnke, Megan Irene; Bosman, Samantha; Spencer, Robert G.; Chanton, Jeff; Jones, Benjamin M.; Bull, Diana L. and McClelland, James W. Biodegradability of organic matter eroding along the Alaska Beaufort Sea coast [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Eroding permafrost coastlines export significant quantities of organic carbon to the marine environment, similar in magnitude to riverine particulate organic carbon fluxes to the Arctic Ocean. Moreover, warming temperatures, declines in sea ice, and other changing climatic variables are increasing the rate of coastal retreat. While erosion mobilizes organic matter primarily in particulate form, this material can be leached to form dissolved organic matter (DOM). This DOM may be incorporated by microbial communities and fuel marine food webs or decomposed to form greenhouses gases like carbon dioxide and methane. Many studies show that permafrost-derived organic matter is rapidly decomposed in soils and freshwater, but few studies examine the fate of permafrost organic matter in seawater. To address this knowledge gap, we designed two laboratory experiments that examine carbon dioxide production and the leaching and biolability of DOM from soil/sediments submerged in seawater. Soil/sediment was cored from rapidly eroding bluffs near Drew Point, Alaska, representing three horizons: active layer soils, Holocene age terrestrial/lacustrine permafrost, and late-Pleistocene age marine-derived permafrost. Geochemical characteristics of bulk organic matter, such as total organic carbon and nitrogen content, stable and radiocarbon isotopes were analyzed prior to experimentation. CO2 production was measured by aerobically incubating bluff material in seawater. To measure leaching yields and biodegradable DOM, soils/sediments were placed in seawater for 24 hours, filtered, and then incubated to measure dissolved organic carbon loss. To interpret differences biodegradable DOM, we examined DOM composition using chromophoric DOM and ultrahigh resolution mass spectrometry (FT-ICR MS). Both experiments demonstrate that erosion supplies highly biolabile carbon. However, there are distinct differences in leaching yields, biodegradable DOM, and CO2 production between bluff horizons. For example, the terrestrial/lacustrine permafrost leaches the most DOM, but this DOM was less biodegradable than DOM leached from the relict marine sediments. These results highlight the need to consider organic matter source and characteristics in order to accurately predict decomposition.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/943129

2022056003 Brovkin, Victor (Max Planck Institute for Meteorology, Hamburg, Germany) and de Vrese, Philipp. Multistability of permafrost carbon storages due to positive water-energy-carbon feedbacks simulated by Earth System model [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The presence of permafrost modulates the interactions between soil water, energy, and carbon cycles. Could the resulting feedbacks be strong enough to support different steady states in permafrost-affected soils, such as dry and organic-poor versus wet and organic-rich, under the same climate conditions? We addressed this question using the land surface model JSBACH, recently updated with an improved soil hydrology and vertically resolved soil carbon pools. We use the model in two simulations driven by atmospheric conditions taken from CMIP6 SSP5-8.5 simulations with the MPI Earth System model. Both simulations receive the same atmospheric forcing, but they start from different initial conditions. One simulation starts from the state for the year 2035, when the model reaches 1.5°C above pre-industrial levels. The second simulation also starts from the state at 1.5°C above pre-industrial, but only after a temperature-overshoot that peaks in 2100, increasing global temperatures to about 4.0°C above pre-industrial levels. From these two very different initial states, we run JSBACH for many thousand years under the same climate conditions corresponding to 1.5°C climate. We show that it takes high-latitude ecosystems and the permafrost-affected soils several centuries to adjust to stable atmospheric conditions. More importantly, the simulations approach different steady-states, with average soil temperature differences of about 0.15°C (at a depth of 1 m) and a difference in land carbon of about 40 PgC on the pan-Arctic scale. The steady-states depend on the soil organic matter content at the point of climate stabilization, which is significantly affected by a warming-induced soil carbon loss due to the temperature overshoot. We conclude that a temporary warming of the Arctic entails important legacy effects and we show that feedbacks between water-, energy and carbon cycles allow for multiple steady-states in permafrost regions, which differ with respect to the physical state of the soil, the soil carbon storages and the terrestrial carbon uptake and -release. We will also report on first results from coupled MPI-ESM simulations with different hydrology setups in permafrost region ("wet" and "dry" Arctic) that significantly affect the climate on global scale through feedbacks to the atmosphere.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/835961

2022057032 Bryant, Marnie (Scripps Institution of Oceanography, La Jolla, CA); Borsa, Adrian A.; Michaelides, Roger J. and Siegfried, Matthew. Exploring coupled surface hydrology and freeze-thaw dynamics around Toolik Lake, Alaska, using ICESat-2 and InSAR data [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0932, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Changes in air temperature, precipitation, and snowmelt have the potential to change patterns of surface and groundwater flow and of heat transport into the active layer. Changes in groundwater flow can impact nutrient cycling and lead to increased flux of dissolved carbon and nitrogen into rivers and lakes. Although continuous permafrost acts as a barrier to groundwater flow, seasonal thawing of the active layer allows for shallow groundwater flow. Permafrost thaw can increase the depth of these shallow aquifers and release water into the active layer, changing patterns of groundwater flow and increasing the groundwater contributions to rivers and lakes. Consistent measurements of surface water are important in tracking hydrological changes. Current efforts consist primarily of in situ monitoring, which is temporally and spatially sparse. The Ice, Cloud, and land Elevation Satellite (ICESat-2) provides elevation measurements at high accuracy and dense along-track spacing, and has been found to provide accurate water level estimates for reservoirs and large lakes. In this study, we compare ICESat-2 water level estimates to in-situ lake level data from Toolik lake to assess the satellite's ability to measure interannual changes in lake levels in Toolik lake and surrounding water bodies that lack in-situ monitoring. We compare water-level changes to seasonal patterns in InSAR-derived surface observations of subsidence and uplift due to thawing and freezing of the active layer. The magnitude and timing of this freeze-thaw cycle relates to the volume of water stored in the active layer and the time interval over which the active layer conducts ground water. We combine ICESat-2, InSAR, in-situ lake measurements, and meteorological data including air temperature and precipitation, to assess the relationship between precipitation, active layer freeze-thaw dynamics, and surface hydrology. By integrating ICESat-2 and InSAR measurements with in-situ data, we can estimate these dynamics over larger scales than can be achieved with in-situ measurements alone, and obtain measurements in areas without in-situ data. Such efforts can help further our understanding of feedbacks between changing permafrost conditions and hydrological systems, with implications for carbon transport, ecosystem, and landscape changes.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/992567

2022057048 Bull, Diana L. (Sandia National Laboratories, Albuquerque, NM); Eymold, William Karl; Flanary, Chris; Nederhoff, Kees; Jones, Craig Alexander; Erikson, Li H.; Chartrand, Chris and Kasper, Jeremy. Evaluation of offshore wave climates along the Alaskan North Slope using K-means clustering [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Erosion and flooding impacts to Arctic coastal environments are intensifying due to increasingly energetic and warm ocean conditions coupling with warming terrestrial permafrost. Nearshore wave propagation models that simulate wave transformation processes to establish onshore conditions from deep water require sufficient boundary conditions. The present study interprets wave, water level, wind, temperature, and salinity data from multiple offshore sites along the North Slope of Alaska to determine a representative subset of boundary conditions in a set of location-independent typologies. We used WAVEWATCH III and Delft3D Flexible Mesh model output from six oceanographic sites located along a constant ~50 m bathymetric line spanning the Chukchi to Beaufort Seas to develop offshore, location-independent typologies. K-means clustering was applied to the energy-weighted joint-probability distribution of significant wave height (Hs) and peak period (Tp) from each site to identify location-dependent cluster centroids for six sea states. Location-independent centroids were determined from the location-dependent spread and subsequent membership to the location-independent centroids was found for each site. Distributions of wave and wind direction, wind speed, and water level associated with these sea states at all sites were assessed to assign single values to describe a simplified, typological rendition of Arctic sea states during both Historic (2007-2019) and Future (2020-2040) timespans. Reanalysis data (e.g. ASRv2, ERA5, and GOFS) grounded the historic simulations while projected conditions were obtained from downscaled GFDL-CM3 forced under RCP8.5 conditions as provided by Scenarios Network for Alaska & Arctic Planning (SNAP). This method reestablishes location dependence for each simulated typology at each site by weighting nearshore results to match their unique statistical occurrence in an average year as defined by centroid membership in the occurrence joint-probability distribution. Increasingly energetic ocean conditions are found in the Future typologies compared to the Historic. These location-independent typologies can serve as offshore boundary conditions to enable computationally efficient simulation of the nearshore along the North Slope of Alaska.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/998963

2022057034 Cai, Jenna (Langley High School, McLean, VA); Hao, Lina; Hao, Xianjun; Qu, John J. and Zhu, Zhiliang. Assessing the impacts of rapid climate change on Arctic soil conditions by combining satellite and in situ measurements [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0934, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic region is undergoing accelerated climate change compared to the rest of the globe: in recent decades, it has had record amounts of shrinking sea ice, glaciers, and snow cover, as well as unprecedented rates of thawing permafrost. This study investigates the consequences of rapidly changing climate on soil conditions around the 1002 area of the Arctic National Wildlife Refuge (ANWR). Trends and patterns of soil moisture, soil temperature, and land surface temperature are explored using NASA satellite measurements and nearby in situ observations from the USDA National Water and Climate Center. In situ soil moisture data over the past decade in Prudhoe Bay (closest data site to 1002 area) illustrates a decreasing trend of -1.003 cm3/cm3/decade at two-inch sensor depth and -2.096 cm3/cm3/decade at eight-inch sensor depth. In situ soil temperature analysis over the past decade in Prudhoe Bay shows an increasing trend of 0.240 K/Decade at two-inch sensor depth. Statistical analysis of land surface temperature data during the past two decades from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Terra Satellite reveals a striking warming trend of 1.206 K/Decade at daytime and 1.269 K/Decade at nighttime over the 1002 area. Soil moisture data from Advanced Microwave Scanning Radiometer 2 (AMSR2), Soil Moisture and Ocean Salinity (SMOS), and Soil Moisture Active Passive (SMAP) satellites all show a similar seasonal pattern and trend over the 1002 area. However, these three soil moisture data products have significant biases, calibration and validation with in situ observations are required to get reliable soil moisture data from satellite measurements for the Arctic region. USGS just installed new soil sensors in the 1002 area, which will be invaluable for more accurate monitoring of the Arctic region.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/906538

2022056014 Cavaiani, Jake (University of Alaska Fairbanks, Department of Biology and Wildlife, Fairbanks, AK) and Harms, Tamara. Antecedent precipitation influence on storage and transport of nitrate and DOM in boreal catchments [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1750, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Increased temperature and precipitation stimulate permafrost thaw, altering the hydrology and biogeochemistry of high-latitude catchments. Permafrost thaw shifts hydrologic flowpaths from shallow, organic-rich soils to deeper, mineral-rich soils, which is hypothesized to diminish organic carbon and increase export of nitrate (NO3-) in high-latitude streams. Thus, solute dynamics in streams might reflect spatial and temporal patterns of permafrost thaw. Solute exports respond to short-term variation in precipitation, which is expected to increase under a warming climate, but the effects of antecedent moisture conditions remain less clear. Transport mechanisms and solute storage can be estimated by observing differences in the concentration-discharge relationship between the rising and falling limbs of individual storm events (i.e., hysteresis). We monitored NO3- and fluorescent dissolved organic matter (fDOM) at high-frequency (15 min) in two streams draining similarly sized catchments of boreal Alaska that contrasted in spatial extent of permafrost due to aspect (north vs. west-facing). Hysteresis relationships were quantified for individual storms occurring in a year of average precipitation (2019) and a wetter year (2020) with >25% more rain than the long-term average. Median annual NO3- concentration was 1.32 times greater and fDOM concentration was 1.35 times greater for the high-permafrost catchment in a wetter year. Hysteresis relationships during storms indicated variation between supply and transport limitation of nitrate in both catchments during 2019, but supply limitation in both catchments during 2020. This suggests that increased precipitation depleted nitrate stores within the catchments. Transport limitation characterized fDOM dynamics in both catchments during 2019, though this effect was weaker in the high-permafrost catchment. In the moderate permafrost catchment, a switch from transport to supply limitation occurred in late summer of 2020. Storm-scale concentration-discharge relationships suggested that extensive permafrost buffered hydrology and biogeochemistry to inter-annual variation in precipitation, whereas solute stores and hydrologic flowpaths were more responsive to variation in precipitation under moderate permafrost extent.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/976957

2022059965 Cheng, Feng (Rice University, Houston, TX); Lindsey, Nate J.; Sobolevskaia, Valeriia; Dou, Shan; Ajo-Franklin, Jonathan Blair and Wagner, Anna M. Watching the Arctic thaw; seismic monitoring of permafrost degradation using distributed acoustic sensing during a controlled heating experiment [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS12A-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Increasing permafrost degradation in response to changing climate conditions in the Arctic is generating permafrost landscapes alteration, increased carbon dioxide emission, and infrastructure damage. These processes threaten the ecosystems that humans depend on for survival at high latitudes. Scalable solutions for monitoring permafrost thaw dynamics are essential to quantitatively understand biogeochemical feedbacks as well as to issue warnings for hazard prevention and control. Unfortunately, a variety of challenges exist for long-term time-lapse monitoring of environmental processes in arctic environments, including (1) affordable dense geophysical arrays to record weeks to months of seismic data, (2) repeatable and automated seismic sources to generate wavefields with rich frequency content (5-100 Hz), and (3) appropriate methods to invert time-lapse seismic waves for near-surface soil properties.In this study, we investigate the feasibility of permafrost thaw monitoring using permanently installed seismic networks. In 2016, Lawrence Berkeley National Laboratory (LBNL) in collaboration with Cold Regions Research Engineering Laboratory (CRREL) conducted a unique artificial permafrost heating experiment in Fairbanks, Alaska. We conducted 2-month continuous active-source seismic monitoring of permafrost thaw with a permanently installed surface orbital vibrator (SOV) as the source and a 4 km continuous 2D array of surface-trenched fiber-optic distributed acoustic sensing (DAS) cable as receivers. Based on time-lapse surface wave dispersion analysis on 4 parallel DAS lines, we observed clear frequency-dependent variations of surface wave signatures, with higher frequency (>15 Hz) contents closely relating to the changing of near-surface soil moisture and lower frequency (<10 Hz) contents spatial-dependently relating to the increasing of permafrost temperature. We developed a comprehensive surface wave inversion workflow to simultaneously invert the observed time-lapse surface waves for a robust and well-constrained 2D time-lapse shear wave velocity (Vs) profile. We interpreted the temporal variations in Vs in the active layer to be related to variations in surficial aquifer state; deeper perturbations in Vs are attributed to increased temperatures and permafrost thaw. The thaw-induced permafrost deformations were also observed on time-lapse horizontal-to-vertical spectral ratio (HVSR) analysis from three broadband seismographs deployed at the site. Further rock physics modelling demonstrated a good match between the predicted velocity changes and the inverted velocity models, indicating a promising avenue for model calibration and thaw monitoring validation. The combination of SOV sources and DAS provided unique seismic observations for permafrost degradation monitoring at the field scale, as well as an observational basis for design and development of early warning systems for permafrost thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/919832

2022059942 Cheng, Yifan (National Center for Atmospheric Research, Boulder, CO); Newman, Andrew James; Swenson, Sean C.; Lawrence, David M.; Musselman, Keith N. and Hamman, Joseph. A novel application and multi-objective optimization of CTSM Arctic hydrology in Alaska and Yukon River basin [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H34B-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic hydrology is an interconnected system, comprising permafrost, snow, glacier, frozen soils and inland river systems, which is experiencing rapid change. Permafrost degradation, early snow-melting and lengthening snow-free season, and warming frozen soil all make it a great challenge to correctly predict hydrologic regimes in the Arctic. In this study, we aim to provide a high-fidelity representation of the aforementioned land surface processes. To this end, we applied the state-of-the-science Community Territory System Model (CTSM) at the subcontinental scale of Alaska and Yukon River Basin to support policy-making on climate adaptation and mitigation for Indigenous Alaskan tribes, which largely rely on the inland river systems for fishing subsistence and transportation of fuel and supplies. This is part of an ongoing interdisciplinary effort being made to combine Indigenous Knowledge with western science (URL: https://www.colorado.edu/research/arctic-rivers/). CTSM is a complex, physically based land surface model that includes complex vegetation and canopy representation, a multi-layer snow model, as well as hydrology and frozen soil physics necessary for the representation of streamflow and permafrost. In addition, we included a subgrid hillslope hydrology parameterization to better capture the fine-scale hydrologic spatial heterogeneity in complex terrain, and updated the input soil textures and organic carbon in CTSM using the SoilGrid dataset. To provide a set of reliable CTSM parameters needed for trustworthy change projections, we performed a multi-objective optimization on snow and river flow using an adaptive surrogate-based modeling optimization (ASMO). ASMO permits optimization through the use of surrogate models to minimize the computational cost. We ran CTSM at a spatial resolution of 4 km using downscaled and bias corrected ERA5 reanalysis data as the meteorological forcings. Five representative river basins across our study domain were selected for optimization with observations of flow at 5 USGS sites, and snow water equivalent at 15 SNOTEL sites. We will discuss the CTSM-ASMO coupling workflow, performance characteristics of the optimization (e.g., computational cost, iterations), and comparisons of the default configuration and optimized model performance.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/978806

2022059972 Chong, Leebyn (National Energy Technology Laboratory, Pittsburgh, PA); Singh, Harpreet; Creason, Christopher Gabriel; Seol, Yongkoo and Myshakin, Evgeniy M. Application of machine learning to characterize gas hydrate reservoirs in permafrost settings [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract OS22A-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The artificial neural network was utilized to train machine learning (ML) models to predict gas hydrate saturation distributions in permafrost-associated deposits in the Eileen Gas Hydrate Trend on the Alaska North Slope (ANS), USA and in the Beaufort-Mackenzie Basin, Northwest Territories, Canada. The database of Logging-While-Drilling (LWD) and wireline well log suites collected at five sites; Mount Elbert, Ignik Sikumi, Kuparuk 7-11-12 (all ANS), and 2L-38 and 5L-38 wells at the Mallik Research Site (Canada) includes more than 10,000 depth points, which was used for training, validation, and testing the ML models. The combinations of two or three well logs were found to be sufficient to predict the gas hydrate saturation at 80-90% accuracy against the NMR-derived gas hydrate saturations. The ML models trained and validated on data from three sites on ANS provide excellent qualitative prediction of gas hydrate content in the sediments at the Mallik site. The results indicate that the ML models trained on data from one basin can be successfully applied to predict key reservoir parameters in another basin. A generalized approach to select a well log combination leading to a better accuracy is discussed.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/912893

2022059951 Churakova, Olga V. (Siberian Federal University, Institute of Ecology and Geography, Krasnoyarsk, Russian Federation); Fonti, Marina V.; Trushkina, Tatyana V.; Zharkov, Mikhail S.; Taynik, Anna V.; Barinov, Valentin; Porter, Trevor John and Saurer, Matthias. Hydrogen isotopes in boreal conifers as indicator of extreme hydrological changes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H51G-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The use of the d-excess in water samples for detection of the water source, atmospheric processes and relative air humidity was proposed in the last century by Dansgaard and has found a wide application in glaciological studies. However, the application of dD in the tree-ring cellulose is still limited and tree-level isotope fractionations unresolved, which complicates the interpretation of dD in tree-ring cellulose. Therefore, new dD measurements are urgently needed, which will increase our understanding of the processes related to deuterium fractionation in tree- ring cellulose and provide complete information about hydrological changes from tree to forest level. The scientific novelty of our project lies in the innovative approach of measuring stable hydrogen isotopes in tree-ring cellulose of different conifer tree species (Larix cajandri Mayr., Larix gmelinii Rupr. Rupr., Picea glauca (Moench) Voss.) from subarctic regions (Russia and Canada) and in the application of deuterium excess (d-excess) to detect eco-hydrological changes recorded by conifer trees to extreme climatic changes (volcanic eruptions, fires, droughts and floods) over the past 1500 years, and in-particular during the recent decades. Our study is highly relevant because the rapid degradation of permafrost in subarctic forests can increase the risk of forest decline. Unique eco-hydrological data on the isotopic composition of dD in tree-ring cellulose combined with the d18O will help us to explain the key centennial hydrological changes in the water source (thawing permafrost water or ground water).

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/796127

2022055946 Churakova, Olga V. (Siberian Federal University, Institute of Ecology and Geography, Krasnoyarsk, Russian Federation); Myglan, Vladimir S.; Fonti, Marina V.; Vaganov, Eugene A.; Kirdyanov, Alexander V.; Naumova, Oksana V.; Kalugin, Ivan A.; Babich, Valery V.; Falster, Georgina; Siegwolf, Rolf T. W. and Saurer, Matthias. Modern aridity in the Russian Altai derived from the tree-ring stable isotopes in the context of the past 1500 years [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A25U-09, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Altai-Sayan Mountain Range (ASMR) is a unique mountain region, representing vegetation from the steppe ecotone to taiga forests, where annual air temperature and precipitation amount vary along strong gradients. Temperature and precipitation changes are crucial for survival of trees at the ASMR, which at the high-elevated sites are growing under severe continental climate in the permafrost zone. The frequency of extreme events increased here over the past decades affecting forests and humans. To determine the amplitude of recent climate fluctuations relative to the long-term natural variability, and evaluate the impact of these changes on the ASMR ecosystems, we have to look into the past by analyzing millennial paleoclimatic archives (tree-ring, ice core, lake sediments) recording both temperature and precipitation signals. The ASMR region is particularly valuable for paleoclimate research because of the existence of old trees and their preservation for millennia. We developed unique annually resolved 1500-year carbon and oxygen larch tree-ring cellulose chronologies (d13Ccell and d18Ocell) for the Tuva Republic (50° N, 89° E, 2300 m asl). Derived July precipitation and air temperature reconstructions from these proxies revealed extremely dry and cold conditions in the 6th and the 17th centuries, opposite to the dry and warm extremes in 10-13th and 21st centuries. Wet and cold periods were limited to the 7th and 14th-16th centuries. Combined with existing paleoclimatic information available for the ASMR, our d13Ccell and d18Ocell data show an overall strong decreasing trend in June-July-August (JJA) precipitation by up to 45% during 1966-2009 CE, compared to the past 535-1965 CE. JJA temperature shows a strong increase of up to 4°C towards 21st century. We conclude that modern arid conditions in the ASMR are the result of simultaneous summer warming and decrease of precipitation, with higher values and fluctuation rate compared to the air temperature over the globe during the past millennia, putting these ecosystem under increasing pressure. Acknowledgments: This work was supported by the Russian National Foundation (RSF, number 19-14-00028) granted to VSM; IK and VB work was conducted under the state assignment of the IGM SB RAS; Swiss National Science Foundation (SNSF 200021_121838/1) granted to MS.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/797869

2022057070 Clark, Jason (University of Alaska Fairbanks, Fairbanks, AK); Tape, Ken D. and Jafarov, Elchin E. Modeling Arctic lakes with the LAKE2.0 model [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-09, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Lakes in the Arctic are important reservoirs of heat with much lower albedo and larger absorption of solar radiation than surrounding tundra vegetation . Under climate warming scenarios, we expect Arctic lake heat balance to shift thawing underlying permafrost. Previous studies of Arctic lakes have focused on ice cover and thickness, the ice decay process, catchment hydrology, lake water balance, and eddy covariance measurements, but little work has been done in the Arctic to model lake heat balance. We applied the LAKE model to simulate water temperatures in three Arctic lakes in Northern Alaska over several years. The LAKE model is a one-dimensional finite-difference model that explicitly solves vertical profiles of water state variables on a finite-difference grid, using a k-e parameterization to calculate turbulent fluxes. We used a combination of meteorological data from local and remote weather stations, as well as data derived from remote sensing, to drive the model. We validated simulated water temperatures with data of observed lake temperatures at several depths. Our validation of the LAKE model completes a necessary step toward modeling changes in Arctic lake ice regimes, lake heat balance, and thermal interactions with permafrost.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/834114

2022057094 Clayton, Leah (Yale University, Department of Earth and Planetary Sciences, New Haven, CT); Schaefer, Kevin M.; Chen, Richard H.; Hoy, Elizabeth; Michaelides, Roger J.; Parsekian, Andy and Hsieh, Ming. Active layer thickness as a function of soil water content in Alaska and Canada [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP55A-1057, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Active layer thickness (ALT) is a critical metric for monitoring permafrost. The influence of soil moisture on ALT is subject to two competing hypotheses: (a) increased soil moisture increases the latent heat of fusion for thaw, resulting in shallower active layers, and (b) increased soil moisture increases soil thermal conductivity, resulting in deeper active layers. To investigate the relative influence of each factor on thaw depth, we analyzed thousands of in-situ soil moisture and thaw depth measurements from the Soil Moisture and Active Layer Thickness (SMALT) dataset, collected at hundreds of sites across Alaska and Canada as part of NASA's Arctic Boreal Vulnerability Experiment (ABoVE). As bulk volumetric water content (VWC) integrated over the entire active layer increases, ALT decreases, supporting the latent heat hypothesis. However, as VWC in the top 12 cm of soil increases, ALT increases, supporting the thermal conductivity hypothesis. Regional temperature variations determine the baseline thaw depth while precipitation may influence the sensitivity of ALT to changes in VWC. Soil latent heat dominates over thermal conductivity in determining ALT, and the effect of bulk VWC on ALT appears consistent across sites.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/943515

2022057029 Cooper, Matthew G. (Pacific Northwest National Laboratory, Department of Atmospheric Sciences, Richland, WA); Zhou, Tian; Bennett, Katrina E.; Schwenk, Jonathon P.; Rowland, Joel C.; Coon, Ethan; Bolton, W. Robert and Fleming, Sean William. Detecting changes in permafrost active layer thickness from baseflow recession [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0929, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost active layer thickness (ALT) is a sensitive indicator of permafrost response to climate change. In recent decades, ALT has increased at sites across the Arctic, concurrent with observed increases in annual minimum streamflow (baseflow). The trends in ALT and baseflow are thought to be linked via: 1) increased soil water storage capacity due to an increased active layer, and 2) enhanced soil water mobility within a more continuous active layer, both of which support higher baseflow in Arctic rivers. One approach to analyzing these changes in ALT and baseflow is to use baseflow recession analysis, which is a classical method in hydrology that relates groundwater storage S to baseflow Q with a power law-like relationship Q=aSb. For the special case of a linear reservoir (b=1.0), the baseflow recession method has been extended to quantify changes in ALT from streamflow measurements alone. We test this approach at sites across the North American Arctic and find that catchments underlain by permafrost behave as nonlinear reservoirs, with scaling exponents b~1.5-3.0, undermining the key assumption of linearity that is commonly applied in this method. Despite this limitation, trends in a provide insight into the relationship between changing ALT and changing Arctic baseflow. Although care should be taken to ensure the theoretical assumptions are met, baseflow recession analysis shows promise as an empirical approach to constrain modeled permafrost change at the river basin scale.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/895212

2022055986 Cox, William (University of Colorado at Boulder, Department of Ecology and Evolutionary Biology, Boulder, CO); Dieleman, Catherine M. and Turetsky, Merritt R. Plasticity of important physiological traits in common boreal plants along a permafrost thaw gradient in interior Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24D-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The boreal biome represents only about 17% of the earth's land surface area but accounts for approximately 60% of global soil carbon. Discontinuous permafrost forms the foundation, both literally and metaphorically, of boreal ecosystems and the services they provide, including long-term carbon storage. However, with polar amplification of current warming trends, the face of the boreal is rapidly changing. Areas of discontinuous permafrost are thawing both gradually and abruptly as temperatures rise and weather patterns change. As abiotic conditions such as site hydrological connectivity, soil temperature, and soil moisture change in response, so too does the boreal biotic community. Building upon our previous work on the effects of thaw on the composition of lowland permafrost plant communities in interior Alaska, here we use fourth-corner and RLQ analyses to assess trends in the physiological traits of those plant communities. Fourth-corner and RLQ analyses are complementary methods to identify ways in which abiotic environmental factors filter species-level physiological traits in the biotic community, where R is a matrix of environmental variables at study sites, L is a matrix of species abundance in those sites, and Q is a matrix of physiological traits of the members of those species. With this method, we found evidence of physiological plasticity in important plant functional traits of dominant flora along a naturally occurring gradient of permafrost thaw. This includes several important functional traits that directly affect the surface and soil microclimate and its capacity for carbon sequestration. Among our findings were reduced stature, aboveground biomass, and specific leaf area of common forest ericoids as well as a reduced capitula density and water retention capacity among common Sphagnum mosses as the active layer thickens. These results demonstrate that the concurrent changes in permafrost plant communities and their physiological traits may drive unexpected and nonlinear changes in boreal ecosystem function in response to northern warming trends and permafrost thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/968586

2022057059 Creamean, Jessie (Colorado State University, Fort Collins, CO); Barry, Kevin Robert; Hill, Thomas Christopher James; Hume, Carson; DeMott, Paul J.; Shupe, Matthew; Dahlke, Sandro; Willmes, Sascha; Schmale, Julia; Beck, Ivo; Hoppe, Clara; Fong, Allison A.; Chamberlain, Emelia; Bowman, Jeff Shovlowsky; Scharien, Randall K. and Persson, Ola P. G. The seasonal contrast of aerosols that can seed ice formation in central Arctic clouds [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C53B-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic is warming faster than anywhere else on Earth, prompting glacial melt, permafrost thaw, and sea ice decline. These severe consequences induce feedbacks that contribute to amplified warming, affecting weather and climate globally. Aerosols and clouds play a critical role in regulating radiation reaching frozen surfaces. However, the magnitude of their effects on surface temperature is not adequately quantified, especially in the central Arctic where they impact the energy balance directly over the sea ice. Specifically, the sources and abundance of aerosols called ice nucleating particles (INPs) that initiate cloud ice formation remain understudied. Until recently, a full year's worth of INP measurements has not been conducted anywhere in the Arctic and no INP data exist from the central Arctic in the winter/spring, creating a significant gap in understanding cloud microphysical processes.Here, we show the very first observations of INPs in the central Arctic for a full year during the Multidisciplinary Observatory for the Study of Arctic Climate (MOSAiC) expedition, spanning the entire sea ice growth and decline cycle. Our results reveal the strong seasonal cycle of INPs controlled by the absence of local open water and long-range transport from lower latitudes in the winter and spring, to enhanced concentrations of INPs during the summer melt, likely from marine biological productivity in local open waters. This unprecedented characterization of INPs will ultimately help inform cloud parameterizations in models of all scales.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/941997

2022059916 Cuesta-Valero, Francisco Jose (American Geophysical Union); Beltrami, Hugo; García-García, Almudena; Gonzalez-Rouco, Jesus Fidel and Garcia-Bustamante, Elena. A perspective on continental heat storage estimates and methods [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC23C-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Earth's radiative imbalance at the top of the atmosphere is of fundamental importance towards understanding the magnitude and evolution of ongoing climate change. This positive planetary energy imbalance increases heat storage in the oceans, continental subsurface, atmosphere, and cryosphere, altering energy-dependent phenomena within each climate subsystem, e.g. sea level rise, permafrost thawing, or extreme heat events. Therefore, quantifying and monitoring the Earth's energy imbalance is important for understanding the non-linear feedbacks on global warming that are in the pipeline, caused by slow responding systems like the cryosphere, which are typically poorly sampled. Despite the success of satellite observations to monitor changes in the Earth energy imbalance, determining the magnitude of the imbalance requires measurements of total heat storage in the Earth system, as well as accounting for the distribution of heat into each climate subsystem.Continental heat storage, the second largest term of the Earth's heat inventory, shows an accelerated increase in recent decades. Analysis of the global network of subsurface temperature profiles has been the main source of information about the long-term evolution of continental heat storage, allowing the global change in ground heat content during the last millennium to be quantified. These estimates also provides an observational reference to evaluate global climate simulations. Nevertheless, most subsurface temperature profiles were measured before the 2000s, which hampers the characterization of the recent warming of the continental subsurface. Furthermore, new approaches are necessary to improve our knowledge of ground heat content at time scales shorter than a decade. Here, we summarize our knowledge about continental heat storage, the methods for estimating ground heat content, and the implications for climate modelling. We also discuss and suggest future steps to complement the available information on the long-term evolution of continental heat storage with new estimates at shorter time scales, for example using satellite data. Expanding the network of subsurface temperature profiles and the remeasuring of sites should be an urgent priority as the subsurface temperature record is being overwritten by current climate change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/798375

2022057028 Daanen, Ronald P. (Alaska Department of Natural Resources, Fairbanks, AK); Liljedahl, Anna K.; Epstein, Howard E.; Gaedeke, Anne and Schulla, Jörg. Simulating Arctic hydrology with WaSiM [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0926, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Climate change leads to rapid landscape change in the Arctic regions. Many aspects of those changes are related to hydrological processes. Arctic landscapes are dominated by ice where it is present in many forms from snow to glaciers and below ground with a variety of ground ice present in permafrost. All the ice depends and cool atmospheric conditions to remain frozen, but in many cases that is currently changing. Ice can be considered long term storage in the arctic hydrological system and the water is often decades to centuries old. Ground ice degradation leads to changes in the topography resulting in modified surface runoff and watershed response to precipitation events. Surface water changes due to permafrost collapse both as the water accumulates in thermokarst pits or lake drainage due to thermal erosion events. Snow is of particular importance as the feedback to subsurface temperatures are strongly dependent on snow depth and density. With warming conditions also comes a change in vegetation and its effects on active layer temperatures and double feedbacks related to snow trapping as the shrub advance continuous in the Arctic. Over the past years we have made progress in the development of the water Balance Simulation Model (WaSiM) toward an arctic hydrological simulation model. Some of the highlights are: soil temperature with freezing and thawing, snow temperature in the snow pack, efficient surface runoff, snow distribution variability, soil surface temperature effects of vegetation through n-factors. We are currently working on the development of a dynamic soil surface collapse module based on a known ground ice content and warming conditions. Surface vegetation conditions are dynamic and simulated by the Arctic Vegetation model (ArcVeg). We are implementing feedbacks from ground ice melt to soil surface collapse affecting surface runoff, local drying and wetting effects on the vegetation. Secondary affects are also considered through preferential snow accumulation in troughs and shrub establishment. The model is uniquely suitable for the simulation of processes on a watershed scale. It is highly efficient and can be used on a high resolution grid that includes the processes of ice wedge polygon collapse and preferential snow accumulation on a meter scale.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/847181

2022057018 Dai, Chunli (Louisiana State University, Department of Civil and Environmental Engineering, Baton Rouge, LA); Howat, Ian M.; Jones, Melissa Ward; van der Sluijs, Jurjen; Nesterova, Nina and Liljedahl, Anna K. Mapping retrogressive thaw slumps using ArcticDEM and machine learning [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C22C-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

A retrogressive thaw slump (RTS) is a crescent-shaped landslide in ice-rich permafrost areas, and its formation is caused by ground ice melt. Previous regional studies have shown an increase in retrogressive thaw slump initialization associated with climate change. Owing to the increased availability and coverage of high-resolution digital elevation models (DEMs) from ArcticDEM, which provides a large collection of 2-meter resolution DEMs for all land areas above 60 degrees North and all of Greenland, Alaska, and Kamchatka, the mapping and quantification of RTS at the pan-Arctic scale is made possible. In this project, surface elevation changes are successfully derived from those time-dependent DEMs, created based on stereophotogrammetry from high-resolution optical satellite imagery, with vertical precisions as good as decimeters. Then, machine learning algorithms are used to automatically detect and classify those changes caused by RTS activities. The training, validation, and test data sets are manually created from the surface elevation change data in Eureka Sound Lowlands, Banks Island, and Peel Plateau, Canada, as well as Yamalsky, Russia. We test and compare the performance of the machine learning algorithm (Mask R-CNN) with different scenarios. The effort to expand our algorithms to the pan-Arctic scale is ongoing. Upon completion, we will produce a 3D dataset of RTS occurrence around the Arctic, enabling us to compare RTS size and volume loss across regions and analyze triggers of mass wasting processes.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/983200

2022057097 Del Vecchio, Joanmarie (Dartmouth College, Hanover, NH); Rowland, Joel C.; DiBiase, Roman A.; Zwieback, Simon and Glade, Rachel. Signatures of permafrost processes in fluvial network morphology and change on the Seward Peninsula, western Alaska, USA [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP55C-1124, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost soils and hillslopes are sensitive to changes in hydrology and temperature, leading to rapid landscape change at high latitudes in response to warming. However, landscape response to high-latitude climate and vegetation feedbacks are poorly understood, making predictions of sediment and carbon release difficult. Sediment delivery from hillslopes may be controlled by topography, which is now readily available at high resolution across the Arctic; by thawing ancient ground ice, the distribution of which is unconstrained; or by heterogeneous soil and vegetation properties. Channel incision is similarly complicated by seasonal variation in thaw depth and timing of precipitation, as well as vegetation patterns. To address this knowledge gap, we studied soil-mantled hillslopes on the Seward Peninsula, western Alaska, where discontinuous permafrost is susceptible to thaw, and a range of sediment transport processes (creep, solifluction, catastrophic movement) coexist on the same hillslopes. Here, landscape dynamics related to thaw must be separated from erosion signals unrelated to permafrost thaw such as other stochastic erosion events and slope and channel response to base-level fall. In analyzing high-resolution topography, we find that Seward Peninsula hillslopes exhibit particularly low drainage density compared to temperate landscapes with comparable soil and bedrock. We attribute this pattern to efficient filling of hillslope concavities by freeze-thaw induced soil movement, as well as limited fluvial incision into frozen mineral soil under a permeable tundra vegetation mat via flow through water tracks, zero-order channels with minimal incision. Although Seward Peninsula drainage networks may be expanding and steepening in response to past lower sea level, water tracks unaffected by this perturbation are experiencing warming-induced subsidence and incision, observed in the field and InSAR-derived subsidence patterns. We predict fluvial networks on permafrost hillslopes to coalesce and incise upslope under future climate and vegetation change, which would instigate erosion and downstream sediment release as well as alter hillslope ecohydrology.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/817453

2022055991 Delcourt, Clément (Vrije Universiteit Amsterdam, Amsterdam, Netherlands); Akhmetzyanov, Linar; Combee, Alisha; Izbicki, Brian; Kukavskaya, Elena A.; Mack, Michelle C.; Maximov, Trofim C.; Petrov, Roman E.; Rogers, Brendan M.; Sass-Klaassen, Ute; Scholten, Rebecca; Shestakova, Tatiana; van Wees, Dave and Veraverbeke, Sander. Fire severity and carbon combustion in larch forest ecosystems of northeast Siberia [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B25M-1649, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In recent decades, climate warming has led to elevated fire activity in boreal forests with increases in severity and extent. This intensification of fire regimes may shift the boreal region from a net carbon sink to a net carbon source. Quantifying and understanding of the drivers of carbon combustion are essential to accurately estimating climate feedbacks from boreal fires. Ecosystem-specific field measurements of fuel consumption are critical to improve fire emissions estimates.Although larch forests account for approximately 20% of the boreal biome, the effects of fire in these ecosystems are largely understudied. Here we synthetized data from 41 field sites collected during the summer of 2019 in Eastern Siberian larch forests that cover gradients of ecosystem types, fire severity and landscape position. Carbon combustion from surface and stand-replacing fires ranged between 1.53 and 4.88 kg C m-2, with a mean of 2.87 kg C m-2 at dense, young, and larch-dominated stands, 3.44 kg C m-2 at open, mature and larch-dominated stands, 4.41 kg C m-2 at mixed pine and larch stands, and 3.30 kg C m-2 overall. Belowground pools contributed in average to 78% of total carbon combustion. We found that both bottom-up (stand age, tree species composition, pre-fire organic soil depth) and top-down (fire weather) drivers influenced carbon combustion within our study sites. To our knowledge, this study is the first to assess the magnitude and controls on carbon combustion from fires in a continuous permafrost terrain in Northeast Siberia. We also evaluated the differenced Normalized Burn Ratio (dNBR) for assessing fire severity within our study area using Sentinel-2 imagery. The dNBR was a relatively strong predictor of the Geometrically structured Composite Burn Index (GeoCBI), a field measurement that assesses fire-induced ecosystem changes. We also found that the dNBR holds some predictive power for estimating burn depth in larch-dominated forests. Our findings provide insight to the effects of fires in permafrost-underlain larch forest ecosystems and calls for additional field calibration to reduce uncertainties in carbon emissions estimates from Siberian forest fires.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/858796

2022057046 Demir, Cansu (University of Texas at Austin, Department of Geological Sciences, Austin, TX); Cardenas, M. Bayani; McKinney, Samuel Tyson; Nguyen, William David; Bristol, Emily M.; Bullock, Emma; Sanders, Aquanette; Schaal, Isabel; Charette, Matthew A. and McClelland, James W. Groundwater flow and transport in a coastal aquifer in the Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Submarine groundwater discharge plays a significant role in the hydrology and biogeochemistry of coastal waters. Role of groundwater in conveying energy and matter to surface waters is particularly crucial along the Arctic coast. In the Arctic, permafrost stores vast amounts of organic matter, and new paths for groundwater flow and organic matter transport emerge due to the change in subsurface ice saturation with rising global temperatures. Therefore, understanding coastal hydrogeology, nearshore groundwater flow dynamics, and their interaction with saline coastal waters in the Arctic is essential. However, the coastal aquifer systems within the continuous permafrost zone are not yet well understood and even sometimes thought to be non-existent. Recent studies show that the corridor between the tundra and lagoons along the Beaufort Sea might host aquifers with little to no ice-bonded permafrost and where energy and matter exchange freely with the lagoons. Following this view, we investigated the extent of ice-free sediment and groundwater flow-transport dynamics in Simpson Lagoon in northern Alaska during the summer. Observations were made along shore-parallel and -perpendicular transects consisting of a beach (supratidal), and the intertidal and shallow subtidal zones. The field methods used include (1) electrical resistivity imaging (ERI) with on-land and submerged electrodes for detecting possible pathways of flow in the unfrozen sediments and, (2) measurements of groundwater level (hydraulic head), temperature, and salinity to explore the discharge and mixing characteristics of the coastal/submarine aquifer. Our results provide novel insight into tundra-lagoon groundwater system dynamics at this particular site and allow for the development of a detailed conceptual model for analogous lagoons along the northern coast of Alaska and other parts of the Arctic.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/998806

2022057088 Dennis, Donovan (GFZ German Research Centre for Geosciences, Earth Surface Geochemistry, Potsdam, Germany) and Scherler, Dirk. Cold regions erosion in a warming world; an evaluation of the temperature-dependence of erosion in the High European Alps [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP51B-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

High-alpine regions are among those on Earth most sensitive to changes in climate and have warmed more than the global average over the last century. Weathering and erosion in cold, high-alpine environments is believed to be controlled by temperature-dependent weathering processes, making these landscapes especially susceptible to climatic changes. Frost-cracking has been shown to set rates of erosion in cold, bedrock hillslopes where temperatures are below freezing for a substantial portion of the year. But studies from the European Alps, North American Cordillera, and the Himalaya have demonstrated that permafrost-thaw-induced rockfalls, a consequence of (warming) temperatures, also contribute non-trivially to the long-term erosion rate in thawing permafrost hillslopes. Continued warming of high-mountain regions may therefore alter the primary means of erosion in these sensitive landscapes. Despite numerous advances, the relative contributions of both erosion mechanisms to long-term erosion rates remains poorly-constrained, notably due to the difficulties associated with extrapolating from short-term observational studies to geomorphologically-relevant timescales. Nevertheless, an improved understanding will not only aid characterisations of temperature-driven erosion on geologic timescales, but also contribute to the development of climate change adaptation strategies, as large permafrost-thaw rockfalls are already responsible for numerous deaths and the destruction of property in alpine areas. Here, we build off our previous work in the Mont Blanc massif evaluating the complex relationship between temperature and erosion rate and expand our evaluation of erosion to consider the entire European Alps. Using in-situ cosmogenic 10Be, we report a new dataset of more than 20 bedrock hillslope erosion rates spanning several orders of magnitude, with preliminary calculations yielding erosion rates that range from 0.01 mm yr-1 to 1.1 mm yr-1. The hillslopes and glacial headwalls sampled span elevations from 2100 m to 4040 m, as well as diverse lithologies, thermal regimes, and glaciation histories. We compare our data against a newly-compiled global dataset of cold, bedrock hillslope erosion rates in order to evaluate current theories of temperature-dependent erosion.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/933051

2022056009 Dieleman, Catherine M. (University of Guelph, Department of Integrative Biology, Guelph, ON, Canada); Kane, Evan S. and Turetsky, Merritt R. Enhanced methane production following simulated nitrogen resource pulse during thaw in lowland permafrost systems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-10, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost soils hold approximately 60% of the Earth's terrestrial carbon, and more than double the carbon reserves found in our current atmosphere. However, climatic warming is increasing permafrost temperatures around the world, rendering these vast carbon stores vulnerable to enhanced decomposition and loss as greenhouse gases. Nitrogen is a limiting nutrient concomitantly released during permafrost thaw events that can stimulate plant and microbial metabolism to either mitigate or intensify carbon release from thawing permafrost soils. Models predict nitrogen release will be both temporally and spatially asynchronous with peak biological productivity, limiting the impact of this permafrost resource pulse on carbon dynamics. We tested these model predictions in situ by injecting 4 g of solid phase urea fertilizer at two soil depths (rooting zone, permafrost thaw front), two seasonal time points (peak biological activity, peak permafrost thaw), and two permafrost thaw conditions (intact permafrost, actively thawing permafrost) from 2017-2019. Throughout this period, we quantified changes in porewater leachate chemistry as well as CO2, and CH4 production rates during the growing seasons (May - Sept). Measurements of dissolved nitrogen showed that the late season nitrogen injection at the permafrost interface was rapidly immobilized at the actively thawing sites. Despite this, ecosystem respiration and net ecosystem exchange of CO2 were unaffected by nitrogen release across all permafrost states. Instead, CH4 fluxes significantly increased at actively thawing sites with N pulse treatments, increasing methane production by up to seven-fold. In combination these results suggest that contrary to modelled predictions, lowland microbial communities can overcome temporal and spatial asynchronies in permafrost resource pulses to intensity carbon emissions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/1006174

2022057084 Douglas, Madison (California Institute of Technology, Pasadena, CA); Lamb, Michael P.; Li, Gen; Rowland, Joel C.; West, A. Joshua; Kemeny, Preston Cosslett; Schwenk, Jonathon P.; Piliouras, Anastasia; Chadwick, Austin John and Fischer, Woodward W. Organic carbon burial by river meandering offsets bank-erosion carbon fluxes in discontinuous permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP35A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic river systems can mobilize organic carbon (OC) from permafrost through riverbank erosion. Because Arctic rivers can be tens of meters deep, they can entrain particulate OC far below the depth of annual thaw, potentially allowing OC to be oxidized into greenhouse gases. However, the amount and fate of permafrost OC mobilized by river erosion remains uncertain. We collected riverbank and floodplain sediment samples along the Koyukuk River, which meanders through discontinuous permafrost in central Alaska, USA. We measured sediment total OC (TOC), total nitrogen (TN), 13C/12C ratios of OC, radiocarbon content, water content, bulk density, grain size, and floodplain stratigraphy. Radiocarbon abundance, TOC, and TN were higher in samples dominated by silt as compared to sand, and we used this relation to map OC content onto floodplain stratigraphy to estimate carbon fluxes due to river meandering. Results showed that sediment being eroded from cutbanks and deposited as point bars had similar OC stocks (125.3±13.1 and 114.0±15.7 kgOC/m2±1s, respectively) regardless of whether the banks contained permafrost. We also observed radiocarbon-depleted biospheric OC in both cutbanks and permafrost-free point bars. These results indicate that a considerable fraction of aged biospheric particulate OC eroded from riverbanks is subsequently re-deposited in point bars, rather than being oxidized to greenhouse gases. The process of aging, erosion and re-deposition of floodplain OC may be intrinsic to river-floodplain dynamics, regardless of permafrost content, and may dampen potential feedbacks between thawing permafrost, river erosion, OC oxidation and climate warming.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/962171

2022057089 Douglas, Madison (California Institute of Technology, Pasadena, CA); Miller, Kimberly Litwin; Schmeer, Maria and Lamb, Michael P. Permafrost riverbank erosion in frozen flume experiments [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP51B-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Erosion of riverbanks within permafrost terrain threatens buildings and infrastructure in many Arctic communities, and has already forced some communities to relocate entirely. Hazard assessment and mitigation would benefit from accurate predictions of riverbank erosion rates in permafrost. Previous work developed a Stefan-based theory for thaw-limited erosion but did not explicitly account for boundary roughness that can affect heat transfer from turbulent water flow to the bank. The theory has been tested against experiments using pure ice, and for sand-ice samples inserted into pipe flow with otherwise smooth walls, but it has not been evaluated in open channel flow with erodible, hydraulically rough, ice-cemented riverbanks. To address this data gap, we designed and ran an open-channel, dynamically scaled flume experiment with a 2-m long eroding bank composed of frozen sand with pore ice. We tracked bank erosion rates using timelapse images and an array of temperature sensors, and measured water discharge, depth, and slope through time. We found that the frozen bank eroded at rates of 1.2 cm/min, approximately twice as fast as predicted from existing theory. We modified the bank erosion model by incorporating theory for heat transfer from turbulent flow to rough boundaries. Preliminary results indicate that riverbank erosion in permafrost is more accurately predicted when accounting for boundary roughness, with implications for predicting erosion rates in warming Arctic rivers.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/951257

2022059960 Douglas, Thomas A. (U. S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK); Jorgenson, Torre; Sullivan, Taylor D.; Saari, Stephanie; Hiemstra, Christopher A.; Nelsen, Patricia and Zhang, Caiyun. Recent widespread permafrost thaw in interior Alaska quantified from geophysical measurements, boreholes, ground-based surveys, and remote sensing [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS11A-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

A large area of syngenetic ice-rich, high carbon content "yedoma" permafrost is present across a 500,000 km2 region in Alaska expanding from the Canadian border west to the Seward Peninsula. This area is warming rapidly and future projections show a dramatic increase in permafrost thaw by 2100. The high ice content makes this permafrost extremely susceptible to thaw disturbance and thermokarst. High carbon stocks in this frozen soil provide a potential carbon source to the atmosphere. A variety of field sites around Interior Alaska provide access to diverse ecotypes and disturbance regimes stemming from infrastructure and wildfire. Eight 300 to 500 m long transects representing a variety of boreal and taiga ecotypes have been studied for the past 10 years. Some sites were burned at different times since the 1980s and others have no recent record of wildfire. Along these transects repeat active layer depth measurements, electrical resistivity tomography (ERT), hourly near-surface permafrost temperatures, 3-10 m boreholes, and repeat airborne Light Distance and Ranging (LiDAR) have been used to measure top-down thaw, map three dimensional discontinuous permafrost bodies, and track thermokarst feature development. Tussock tundra and spruce forest ecotypes have yielded the lowest mean annual near-surface permafrost temperatures. Mixed forest ecotypes are warmest, exhibit the highest degree of recent warming, and have the highest prevalence of thaw degradation. Thermokarst features, residual thaw layers, and taliks have been identified at all sites and they have been expanding since 2013. Repeat airborne LiDAR measurements show the lateral expansion of wetland features along thawing margins as well as meters of top-down thaw and ground surface subsidence at some sites. Deep boreholes confirm ERT measurements that show a permafrost thickness of ~40 m. Our measurements, along with long-term records from yedoma sites across Interior Alaska, show widespread near-surface permafrost thaw since 2010. A projection of the increase in thaw depth, by ecotype, across the Interior Alaska yedoma domain yields a first-order estimate of 0.44 Pg of organic carbon in thawed permafrost soil since 2013. Though the ultimate fate of this soil carbon is unknown the amount of carbon is roughly equal Australia's yearly CO2 emissions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/961055

2022055957 Doyle, Shawn (Texas A&M University, Department of Oceanography, College Station, TX) and Christner, Brent. A meta-analysis of microbial communities in basal ice and other sympagic environments [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B12C-08, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The basal ice of glaciers is an important transient phase and among the least explored areas of the cryosphere. The export of basal material in meltwater from glaciers and ice sheets is recognized as a major source of labile organic matter, nutrients, and trace metals to environments receiving discharge from glaciated watersheds. Although viable microbes entrapped in basal ice have been assumed to be metabolically dormant, studies of ice cores in Greenland and Antarctica have provided evidence that microorganisms conduct active biogeochemical processing of organic matter while frozen within basal ice matrices. As such, basal ice microbiomes may be an important but unconstrained aspect of biogeochemical cycling in the cryosphere. However, due to the logistical difficulty in accessing and sampling basal ice environments, current understanding of their microbiological composition and activity is still quite limited. In this study, we use a combined DNA- and RNA-based 16S rRNA amplicon analysis coupled with measurement of viable biomass to examine the composition, diversity, and activity of microbial communities from the basal ice of cold-based and temperate glaciers. Our results indicate that different types of basal ice-even those adjacent to each other within the same glacier-harbor distinct microbiomes. Ice temperature and age appear to be important predictors of the diversity of metabolically active taxa within these microbiomes. We paired these results with a meta-analysis of microbial diversity observed across different permanently frozen environments within the cryosphere, providing a broad overview of the specific microbial lineages enriched in different types of basal ice, glacial ice, permafrost, and cave ice. This effort revealed that the microbial communities in debris-rich basal ice of cold-based glaciers are only distantly related to those in englacial or supraglacial ice and are instead most like those found in permafrost. Although more data from other cold-based glaciers and regions are needed to test if these similarities with permafrost are robust across multiple spatiotemporal scales, this finding suggests the abundant amount of information on permafrost environments could be applied to make new strides in our understanding of basal ice microbiology.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/977363

2022057093 Draebing, Daniel (University of Bayreuth, Department of Geomorphology, Bayreuth, Germany); Mayer, Till; Jacobs, Benjamin and McColl, Samuel Thomas. How frost weathering drives erosion in high alpine environments [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP54B-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The breakdown, erosion, and evolution of alpine rockwalls is governed by a set of geological and environmental factors that are seldom investigated holistically. We explored the combined roles of frost weathering, permafrost, and glacier retreat on alpine rockfall, and tested the effects of lithology and elevation in the Hungerli Valley, Swiss Alps. We (i) simulated frost weathering in the laboratory on rock samples, (ii) modelled frost weathering and permafrost at the rockwall scale, and (iii) compared frost cracking, glacier retreat history and permafrost distribution to measured rockwall erosion from terrestrial laser scanning. (i) At the laboratory scale, we simulated volumetric expansion and ice segregation in predefined cracks on three rock samples of different lithologies. Our results showed that short-term volumetric expansion can cause critical stresses, however, these stresses unlikely occur in the field due to prerequisite high saturation levels. In contrast, ice segregation caused subcritical stresses below 1 MPa that can progressively crack rocks. (ii) At the rockwall scale, we used temperature records to run thermo-mechanical frost cracking models that incorporate rock strength and hydraulic properties. The modelled frost cracking patterns are consistent with measured fracture spacing. Frost cracking patterns strongly correlate with elevation, revealing a topographic control on frost weathering. (iii) At the catchment scale, erosion rates correspond to all three processes investigated; frost cracking, the spatial distribution of mean annual rock surface temperature (MARST) as proxy for permafrost occurrence, and deglaciation age as proxy for paraglacial adjustment. Moreover, all three show a dependence to elevation. In summary, our study suggests that the erosion of rockwalls in high mountain areas is driven by a quantifiable combination of frost weathering, paraglacial, and permafrost processes. Elevation is a key factor that influences the efficacy of all three processes, while lithology has an overall smaller effect.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/880817

2022057031 Eklof, Joel (University of Washington, Department of Civil, and Environmental Engineering, Seattle, WA); Waldrop, Mark P.; Dafflon, Baptiste; Jones, Benjamin M.; Tao, Jing and Neumann, Rebecca Bergquist. High-resolution thaw dynamics of two latitudinally distant Alaska thermokarst sites; a field study [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0931, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost thaw and resultant landscape change have a net warming effect on the climate. Northern high latitudes are projected to get warmer and wetter in the future which will affect rates of permafrost thaw and the mechanisms by which thaw occurs. To better understand changing thaw dynamics, we instrumented two actively thawing permafrost features: 1) an isolated permafrost plateau in south-central Alaska with currently warm and wet climate conditions that mirror those expected in more northern permafrost regions in the future, and 2) a site in Interior Alaska that is experiencing more typical subarctic climate conditions. Thaw dynamics at the two sites were observed with a dense instrumentation network of 82 distributed temperature profilers (DTPs). Installed DTPs measured temperature every 10 cm from the soil surface into the permafrost table, which ranged from 46 cm to 220 cm below the ground surface, at a 15-minute measurement interval. These data, in addition to accompanying groundwater, meteorological, soil moisture, frost probe, and vegetation data, are explored to further define the environmental factors that contribute to permafrost thaw. One such contributing factor is the thermal impact of rain. In 2019, before installing our DTPs and soil moisture sensors, we observed rapid thaw directly following a July rain event at some sensor locations of the south-central permafrost feature. During this event, more than half of the seasonal frost (~30 cm) thawed in less than a week. If similar warm rain events occur during the 2021 summer season, we will explore the relative thermal contributions of direct advective heat transport to that of increased soil thermal conductivity after rain using our new instrumentation. Our efforts to better understand the environmental factors that lead to thaw and to determine the rates at which permafrost thaws under different climate conditions will allow for better preparation, modeling, and policymaking for the future.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/996367

2022057006 Euskirchen, Eugenie Susanne (University of Alaska Fairbanks, Fairbanks, AK); Edgar, Colin; Kane, Evan S.; Turetsky, Merritt R. and Waldrop, Mark P. Remarkable interannual variability in the carbon sink strength of an Alaskan boreal peatland complex based upon a decade of eddy covariance measurements [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B53A-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost degradation in peatlands results in changes in vegetation and soil properties which may impact net carbon storage. To better understand these dynamics, we established four sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, two internal collapse scar bogs of different ages formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2), methane (CH4), water, and energy fluxes, as well as associated environmental variables. Based on just over a decade of measurements, from 2011-2021, we found that these ecosystems acted as sources of CO2 and CH4 to the atmosphere. However, the interannual standard deviation in net ecosystem exchange (NEE) was high, approximately 100 g C m-2 y-1, which is twice of what has been previously reported for the interannual standard deviation in NEE across other boreal sites. This interannual variability was due to changes in the environmental drivers. In particular, some recent years experienced nearly twice the amount of average rainfall, and other years were marked by increases in snowfall and late snowmelt coupled with warming winter soil temperatures. Furthermore, changes in both gross primary productivity and ecosystem respiration contributed to this variability. Finally, not only is interannual variability remarkable, but given that these sites are in close proximity to one another (≤&eq;1 km2 apart), the variability within this small section of the landscape is also remarkable as the NEE estimates at the sites could have nearly opposite responses to the environmental drivers. These findings have implications on the uncertainty ranges of data used in benchmarking carbon cycle models and also emphasize the necessity of such long-term measurements in a changing climate.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/918706

2022055979 Farina, Mary (Montana State University, Bozeman, MT); Beck, Madeline; Watts, Jennifer; Powell, Scott L. and Natali, Susan. Exploring environmental conditions driving high spatial variability in CO2 and CH4 fluxes in a boreal wetland [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B22D-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Rapid warming in boreal ecosystems has led to permafrost degradation and changes in wetland distribution, affecting land-atmosphere exchanges of carbon dioxide (CO2) and methane (CH4). Quantifying ecosystem change and carbon fluxes is especially difficult in boreal wetlands due to high spatial heterogeneity. There is a need to improve modeling approaches to estimate carbon budgets across the boreal zone and to monitor whether increasing CO2 and CH4 emissions are reducing overall carbon sink status. To better account for spatial heterogeneity in carbon fluxes, we need information on the primary drivers of flux - including vegetation type and soil thermal and moisture conditions - mapped continuously in high spatial detail. Imagery from unmanned aerial vehicles (UAVs) can be used to obtain this information at very high resolution, providing new detail about landscape heterogeneity and fine-scale processes that control fluxes. In this study, we investigate the Big Trail Lake boreal wetland site in interior Alaska. The wetland is highly heterogenous in terms of vegetation composition, microtopography, and soil moisture. During a field campaign in Summer 2021, chamber-based CO2 and CH4 flux and soil variables (soil temperature, soil moisture, and soil pH) were sampled across the site, and UAV flights were conducted to collect high resolution multispectral and thermal imagery. We are using the newly collected data to identify and map drivers of the complex patterns of carbon flux observed within the wetland, including local hotspots of CH4 emissions. We expect that accounting for fine-scale spatial drivers of carbon flux will greatly reduce uncertainties in carbon budget accounting for landscape-to-regional level assessments.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/951632

2022057023 Farquharson, Louise Melanie (University of Alaska Fairbanks, Fairbanks, AK); Nicolsky, Dmitry; Irrgang, Anna M.; Romanovsky, Vladimir E.; Jones, Benjamin M.; Xiao, Ming; Liew, Min and Gibbs, Ann. Permafrost thaw and coastal erosion between 1950 and 2100 at three coastal communities in Arctic Alaska, past observations and future projections [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C25F-0883, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost thaw and coastal erosion are expected to cause widespread land loss, infrastructure damage, the re-routing of tundra and snow travel corridors, and the destruction of important cultural sites across many communities within the next century. We use a combination of remote sensing, digital elevation analysis, and ground temperature modelling to explore past and future permafrost dynamics and shoreline change at Wainwright, Point Lay and Kaktovik on the North Slope of Alaska. Geophysical Institute Permafrost Laboratory (GIPL) results suggest that by the year 2100, under Representative Concentration Pathway (RCP) 8.5, ground temperature could increase by 6 to 8°C (from ca. -5°C to ca. +1°C) under natural conditions (i.e. tundra) and by 7 to 9°C (from ca. -6°C to ca. +1°C) in areas covered by 1 m of gravel (e.g. roads and runways). The projected increase in ground temperature at 1 m depth will result in above freezing conditions at all sites. Due to the prevalence of ground ice this will lead to widespread subsidence and thermokarst development both within and around all three communities. The difference in ground temperature change between natural and gravel conditions highlights the potential for accelerated permafrost thaw within the built environment. Maximum historical average rates of shoreline change between ca. 1950 and ca. 2020 were -1.34 m/yr, -1.67 m/yr and -4.3 m/yr at Point Lay, Wainwright, and Kaktovik and their adjacent coastlines respectively. We analyze historic rates of change to explore different shoreline change scenarios (a conservative increase vs an amplified increase in erosion rates) and create coastal erosion projections through 2100 for all three communities in order to quantify land loss and identify both cultural sites and infrastructure that will likely be lost or damaged during this time period.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/989649

2022055947 Feng, Yan (Argonne National Laboratory, Argonne, IL); Hamilton, Douglas Stephen; Quinn, Patricia and Gao, Yuan. Influence of high-latitude dust on aerosol radiative effects and deposition in the DOE Earth system model [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A32B-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Recent studies suggest that high-latitude dust sources play an important role in the Earth System, especially through the influence on glaciation of Arctic low-level clouds, snow albedo, and iron supply to the ocean and snow/ice biogeochemistry. Although the physical processes controlling dust emissions in high latitudes are similar to temperate regions, there are additional processes specific to cold regions such as soil properties, strong winds, permafrost, glacial retreat, and snow-melt processes all of which can affect the efficiency of dust emissions, its physicochemical properties, and distribution of aerosol deposition. There is currently lack of efforts to quantify the characteristics and climate impact of high-latitude dust represented in the Earth System models.In the present study, a physically based vertical flux theory (Kok et al., 2014) is implemented to the DOE Earth System Model (E3SM) for dust generation. It calculates the time-dependent soil erodibility interactively based on the model-predicted soil moisture and fractional areas of bare ground (no vegetation or snow cover), enabling the coupling of dust emission with land surface changes within high latitudes. In the high latitudes (> 60°N or 40°S), there are evident increases of dust emissions. Annual emissions of the high-latitude dust with the new method contribute to about 1»2% of the global dust total under present-day condition, which is consistent with observationally based estimates. The high-latitude dusts peak in both winter and summer-to-fall months in the Arctic but only appear to be a large source in the Southern Hemisphere during Austral summer. The winter Arctic dust is driven by the high winds associated with the sub-arctic low, while summertime high-latitude dust particles in both hemispheres are emitted from ice-free land surfaces. The local dust sources are shown to provide an important source of ice-nucleating particles and nutrient iron supply in summer when the long-range transport of aerosols from the mid-latitudes is limited. The E3SM dust simulations are compared with the long-term surface measurements at the DOE/ARM Barrow site in Alaska and the shipboard measurements of dust deposition fluxes in the high latitudes as well as the CESM2 model results. The contribution of high-latitude dust to the surface and top of the atmosphere energy balance will also be presented.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/971491

2022059919 Field, Leslie A. (Stanford University, Department of Electrical Engineering, Stanford, CA); Strawa, Anthony W.; Manzara, Anthony; Johnson, Doug and Das, Soumitra. Saving glacial ice through localized surface albedo modification [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC35E-0748, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

It is well known that global warming has had an outsized effect in the Arctic and Himalayas. Temperatures in the Arctic have risen 2-3 times faster than the rest of the planet, threatening glaciers in Greenland and the Himalayas. The loss of glacial ice and the higher temperatures have already had a devastating effect on the people, flora and fauna in the Arctic and Asia. Approximately 70 percent of the infrastructure in the global Arctic region is built on permafrost and much of this is at risk due to rising temperatures. Freshwater runoff from Greenland's glaciers is accelerating, and could cause a future disruption of the Atlantic Meridional Overturning Circulation (AMOC), which would further disrupt historic weather patterns in Europe and North America. Complete melt of Greenland's glaciers would add 7 meters to sea level rise, inundating coastal communities worldwide.Ice melt in the Himalayas (the third pole) leads to another set of humanitarian and environmental problems of absolutely critical international importance. The glaciers are retreating so rapidly that the central and eastern Himalayan glaciers could disappear by 2035. The melting is threatening the life of the 240 million people who live on the mountains and hills. These glaciers feed 10 largest rivers in Asia, and nearly 1.7 billion people depend on these rivers for drinking water, agriculture, and hydroelectric power, while 3 billion people consume the food produced in these river basins. The rapid retreat and disappearance of these glaciers would have devastating impacts on these people and could destabilize the world. This paper posits that the Arctic Ice Project's technology of Surface Albedo Modification that is proposed to preserve and regrow sea ice can also be used effectively to prevent glacial melt and stabilize Arctic infrastructure. A heat transfer analysis supports this idea. A phased approach toward proof-of-concept studies in Greenland and the Himalayas is also presented.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/963863

2022057090 Fields, Jordan (Dartmouth College, Department of Earth Sciences, Hanover, NH); Perrotti, John; Dethier, Evan and Renshaw, Carl E. Climate-driven changes to channel erosion rates in the Mackenzie River basin since 1985 [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP51B-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Recent work in high-latitude regions has shown that permafrost is melting at an unprecedented rate, with important implications for global greenhouse gas emissions. Yet, the fate of carbon-rich sediments depends partially on if, and how, they are mobilized in the environment. Here, we ask whether channel-floodplain interactions of high-latitude rivers have changed as Arctic temperatures have warmed. Using satellite imagery from 1985-2020 at ~4,500 study sites across the entire Mackenzie River Basin in the Canadian Arctic, we show that channel migration rates have increased throughout the basin over the study period. However, changes in channel erosion are non-uniform. River channels at the basin's middle latitudes (58.72-62.72°N) have experienced more rapid change than those at the southern and northernmost latitudes. In those middle latitude channels, the annual bank area eroded per 5 years has increased >50% on average since 1985. Additionally, lower-order river channels have experienced greater planform changes than the main stem of the Mackenzie. Rather than directly responding to the absolute magnitude of temperature change, our data show that regions experiencing the most rapid increase in channel migration rate are those areas experiencing the most rapid increase in degree days (summed degrees above 0°C for each day). To the extent that the rate of change in degree days drives permafrost melting, these results suggests that the increase in erosion rates may be driven by changes in permafrost extent. Yet, significant variance in the data remain unexplained by temperature alone, especially at the highest latitudes, and we therefore discuss potential variables driving changes in the arctic beyond rising temperatures.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/997311

2022056024 Frederick, Jennifer Mary (Sandia National Laboratories, Albuquerque, NM); Eymold, William Karl; Nole, Michael; Conley, Ethan W. and Wagman, Benjamin M. Quantifying the known unknown; including marine sources of greenhouse gases in climate modeling [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45K-1763, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Researchers have recently estimated that Arctic submarine permafrost currently traps 60 billion tons of methane and contains 560 billion tons of organic carbon in seafloor sediments and soil (Sayedi et al. 2020), a giant pool of carbon with potentially large feedbacks on the climate system. For comparison, humans have released a total of »500 billion tons of carbon into the atmosphere since the Industrial Revolution. Unlike terrestrial permafrost, the submarine permafrost system has remained a "known unknown" because of the difficulty in acquiring samples and measurements. Consequently, this potentially large carbon stock never yet considered in global climate models or policy discussions, represents a real wildcard in our understanding of Earth's climate. This presentation will detail current work towards quantifying Arctic methane gas releases from the sediments to the water column, and potentially to the atmosphere, where positive climate feedback may occur. Newly developed modeling capability at Sandia National Laboratories and the U.S. Naval Research Laboratory now gives us the ability to probabilistically map gas distribution and quantity in the seabed by using a hybrid approach of geospatial machine learning, and predictive numerical thermodynamic ensemble modeling. The novelty in this approach is its ability to produce maps of useful data in regions that are only sparsely sampled, a common challenge in the Arctic, and a major obstacle to progress in the past. By applying this model to the circum-Arctic continental shelves, and integrating the flux of free gas and dissociating gas hydrates from the sediment column under climate forcing, we aim to provide the most reliable estimate of a time-varying source term for greenhouse gas flux that can be used by global oceanographic circulation and Earth system models. The result will allow us to better understand the wildcard of the submarine permafrost carbon system, and better inform us about the severity of future national security threats that sustained climate change poses. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. SAND2021-9330 A.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/872152

2022057042 Gao, Bo (Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN) and Coon, Ethan. Analysis of the impact of physics representation on permafrost modeling [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0943, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost degradation due to climate change is expected to affect the hydrology and ecology of the Arctic system, which will further impact human infrastructure and Arctic communities. To reduce the potential damage, better understanding and representation of Arctic physics is required for improved prediction of permafrost dynamics. Generally, incorporating full physical processes will improve modeling accuracy, while also resulting in increased runtime. Any numerical experiment must choose between representing more complex physics and computational expense. Therefore, the purpose of this work is to provide permafrost hydrology modelers important references for better choosing the right model representation for a given modeling experiment by formally studying the tradeoff between complexity and runtime under relevant physical metrics. Specifically, this work will discuss the following three common physics simplifications in permafrost modeling, as well as the corresponding hydrological responses: (1) assuming equal density of ice and liquid water in frozen soil; (2) neglecting advective heat transfer during soil freezing and thaw; (3) neglecting the cryosuction effect in unsaturated freezing soil. We will show a comparison between assuming the simplification and including full physics for the three cases using various modeling scenarios that explore different scales, distinct soil properties and meteorological conditions from different sites. The results of this comparison show the influence of the representation of these physics on active layer thickness, evaporation, discharge, and local temperature and water content, demonstrating the sensitivity of these metrics to each of the processes considered.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/924133

2022056000 Gay, Bradley (George Mason University, Department of Geography, Fairfax, VA); Armstrong, Amanda Hildt; Montesano, Paul; Osmanoglu, Batuhan; Schaefer, Kevin M.; Epstein, Howard E. and Ranson, Kenneth. Understanding active layer thickness variability under changing climatic conditions across the North American taiga-tundra ecotone [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31E-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In Alaska, pervasive irregularities of permafrost coverage and associated boreal forest heterogeneity within the North American Taiga-Tundra Ecological Transition Zone (TTE) are becoming more apparent as the climate warms. These anomalies correspond to extensive shifts in active layer thickness (ALT), carbon cycle disruption, and ecosystem response patterns. The feedback complexities associated with these climate-induced disturbances are evaluated with the integration of remote sensing, modeling, field observations, data assimilation and harmonization techniques, and artificial intelligence technology. In this study, to improve our understanding of shifting belowground dynamics and how they associate with aboveground vegetation patterns, we used the SIBBORK-TTE model to derive permafrost degradation and ecosystem transiency at high-resolution in this study. The intercomparison of model version output was first examined; then, multiple verification and validation methodologies revealed distinct historical and future implications resulting from ALT variability within four regions of the Alaska TTE domain (North Slope, Yukon Delta, Seward Peninsula, Interior). To quantify historical thaw variability and identify seasonality patterns across these regions of interest, in situ ALT point measurements were collected from two campaigns (CALM, SMALT) to cross-validate ALT-derived SAR data (AirMOSS, UAVSAR) and below-ground SIBBORK-TTE simulations between 1990-2020. Future conditions were then projected with a warming climate function and CMIP6 data from CNRM-CERFACS SSP126/585 scenarios. Initial results for derived and measured annual maximum ALT yield a mean-error performance metric of 0.2294. Paradoxically, future climate conditions advance the ubiquity of permafrost thaw and seasonality widening across the TTE. With this investigative approach, spatiotemporal variability in ALT provides a unique signal to enhance model precision and lower uncertainty through fine-tuning driver forcing and modular parameterization, forecast permafrost distribution, and identify the climatic and topographic mechanisms of earth system feedbacks and land cover change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/979064

2022055959 Genet, Helene (University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK); Jafarov, Elchin; Rogers, Brendan M.; Natali, Susan and Watts, Jennifer. The Arctic carbon monitoring and forecasting system; a novel forecasting framework to build new understanding and reduce model uncertainty of the permafrost carbon-climate feedback [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15A-1409, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In light of the magnitude and pace of the environmental changes in the northern permafrost zone (NPZ) and their feedbacks to climate, contemporary, accurate and quantitative ecological forecasting has never been so paramount to the development of climate change adaptation and mitigation strategies. Yet, uncertainties associated with carbon (C) projections in the NPZ remain the largest to projections of global C budget and climate. While there are persisting lacks of data documenting important and emerging soil and vegetation dynamics in the NPZ, the volume, variety and accessibility of observational data in the NPZ has grown exponentially over the past decades and significantly improved our understanding of terrestrial C dynamic. Yet, a lag persists between large availability of historical, new and iterative data collections and the capacity of terrestrial biosphere models to fully incorporate this information, limiting advances in reducing the uncertainty of ecological forecasting in the NPZ. In this new project, we are developing the Arctic Carbon Monitoring and Prediction System (ACMPS), a data assimilation system that will use the information from field observations from ecological networks, remote sensing data and ecological modeling to reduce the uncertainty of the terrestrial carbon balance in the NPZ. The ACMPS will be coupling model development and testing, data-assimilation techniques and near-term forecasting capacity to improve the accuracy of historical and future simulations of ecosystem permafrost and C dynamics across the NPZ. We will present the structure and workflow of the ACMPS, as well as preliminary assessment of model sensitivity and uncertainty analysis of soil and vegetation carbon fluxes, using a terrestrial biosphere model specifically developed to represent permafrost, vegetation and carbon dynamics in arctic and boreal ecosystems.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/962951

2022059915 Gering, Skylar (Harvey Mudd College, Claremont, CA); Dorheim, Kalyn; Ha, Natanel; Fuhrman, Jay; Woodard, Dawn and Bond-Lamberty, Benjamin. Using a simple climate model to track global carbon flows under negative-emissions scenarios [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC15C-0707, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Computationally efficient simple climate models are valuable tools for large-ensemble sensitivity studies, rapid-turnaround analyses, and model coupling experiments. One example is Hector (URL: https://github.com/JGCRI/hector), an open-source model featuring an adaptive timestep solver, multiple biomes, ocean chemistry, and a novel permafrost implementation. We developed a new feature for this model: the capability to track the flow of carbon from one carbon pool (e.g., atmosphere) to another and report, at the end of a model run, the origin of the carbon within each pool. Our implementation thus records the origin pools of the carbon in every model pool, determined at the start of a run or some user-defined timepoint; if carbon tracking is enabled, this origin record is updated every timestep to reflect the model's carbon fluxes (pool-to-pool transfers). To demonstrate this capability, we reconstruct and visualize the movement of carbon for several negative-emission runs, deep decarbonization scenarios in which technologies such as direct air carbon capture and storage sequester atmospheric carbon. This allows us to understand the sources of the removed carbon, in spite of the model's complex feedbacks and internal carbon cycling. Hector is the only simple climate model that we are aware of with this ability, which opens up opportunities for deeper exploration of the effects of human intervention in the global carbon cycle, as well as supporting future model development such as carbon isotopes.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/845663

2022057075 Gibbs, Ann (U. S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA); Erikson, Li H.; Engelstad, Anita; Jones, Benjamin M. and Richmond, Bruce M. Influence of waves and temperature on permafrost bluff retreat at Barter Island, NE Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP22A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Coastal permafrost bluffs are highly vulnerable to climate change, as their erosion is largely driven by a combination of thermo-mechanical and thermo-denudational processes. Despite this vulnerability, the understanding of how Arctic permafrost bluffs change through time is poor because of the limited archive of observational data. Barter Island, Alaska located on the coast of the Arctic National Wildlife Refuge, is one of few locations where an extensive observational dataset exists which allows for a detailed assessment of coastal change trends over decadal to annual time scales.At Barter Island, bluff-edge positions were delineated from maps, aerial photographs, and satellite imagery acquired between 1950 and 2020, and at a nearly annual rate since 2004. Change rates and retreat distances were calculated on 332 transects spaced 10-m alongshore. On average, bluffs retreated 114 m during the 70-year period (-1.6±0.1 m/yr), with a maximum value of 163 m. Annual rates of change were highly variable, with individual years having retreat rates over 4x higher than the long-term average (-6.6±1.9 m/yr; 2012-2013). Both long-term (multi-decadal) and short-term (annual/semi-annual) rates show a steady increase in retreat through time, with consistently higher rates since 2015, suggesting an acceleration in retreat that is independent of large spatial and temporal variations observed on an annual basis.Rates and patterns of bluff retreat were correlated to likely drivers of coastal change, including modeled incident wave energy, and air and water temperatures. Wave energy was found to be the dominant driver, followed by sea-surface temperatures and warming air temperatures that were used as proxies to evaluate thermo-erosion and denudation. Acceleration in retreat rates at Barter Island may be related to increases in both thermo-denudation, associated with increasing air temperature, and the number of niche forming and block collapsing episodes associated with higher air and water temperature, more frequent storms, and longer ice-free conditions in the Beaufort Sea.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/954111

2022059949 Goldtooth, Aaron (University of Arizona, Tucson, AZ); Agnihotri, Jetal; Neto, Antonio Alves Meira and Niu, Guo-Yue. Impacts of warming on frozen soil permeability over the Ohio River basin through recession flow analysis [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H45D-1210, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

There has been preliminary research into the use of recession flow analysis of catchment areas to measure permafrost thawing rates due to warming. These results indicate a correlation between changes in permafrost depth and coverage and recession flow data in regions that support frozen soils. Here, we aim to test this hypothesis in the Ohio-Tennessee combined river basin--a snowmelt-dominated watershed in the US to further generalize these relationships. The Ohio-Tennessee River Basin in North America covers a large area in the Midwestern United States, from the Appalachian range to the Mississippi River basin and from the Great Lakes region to just south of Tennessee. The basin covers 189,422 square miles (490,600 km2), the 8th largest in the US, with the 2nd largest discharge rate. The USGS has a network of streamgage sites throughout the Basin that have discharge flow rates from as far back as 1933, well before the current warming period that began approximately in the 1980s. Having such an elaborate dataset will prove to be valuable for demonstrating the efficacy of recession flow analysis in catchment areas that lie below subarctic latitudes (below 50°N latitude). Changes in recession of the streamflow (drainage of groundwater) due to warming should be reflected in higher permeability of frozen soil due to lower ice content. Recession flow analysis of seventy-year long streamflows from eleven streamgages spread throughout the Ohio-Tennessee River basin showed decreasing trends in nine gauges for permeability over time with the greatest changes coming from streamgages within the largest sub-basins and the strongest trend correlations due to latitude. In the future, further research goals may include an analysis over other river basins that are more affected by frozen soil in higher latitudes to further test the effects of latitude on results. Additionally, running analyses of air temperature and snow depth using mechanistic modeling (with process-based land surface models) could provide more information on the overall shift in climate of a basin area.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/993859

2022059976 Gorkavyi, Nick (Science Systems Applications, Lanham, MD). Investigation of geomorphological signatures of permafrost in the polar lunar areas with VIPER [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract P55E-1979, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

A study of images of the polar regions shows that small craters near the poles of the Moon are distinguished by the following features: 1. they have a smoother shape--see Fig (a); 2. patterned ground ("wrinkled skin") is often observed in and around the crater--see Figs (a,b,c); 3. outside the craters landslides and cracks are noticeable--see Fig (d); 4. layers or scarps are often visible on the inner slope--see Fig (e). These features (scarps and patterned ground) are typical for Martian craters in the permafrost zone (see Fig f), as well as for similar zones on Earth. It is hypothesized that these features of lunar craters are associated with the presence of permafrost in the polar regions of the Moon. In 2023, the VIPER rover will investigate the distribution of ice (volatile) deposits in the region of the Moon's South Pole. VIPER navigation cameras represent a unique opportunity for the geomorphological analysis of the lunar surface and the study of physical properties of regolith due to multiple key factors: - A large number of high-quality digital images with a good resolution of the South Pole of the Moon, which is a key region for the landing of manned expeditions. - A low position of the Sun, which generates long shadows, creates favorable conditions for object recognition algorithms. - A presence of a rover track in the images enables VIPER wheels to be used as tools for the study of the regolith and the development of a geotechnical model of regolith in the South Pole region. Rover navigation cameras will allow investigation of the distribution and shape of small craters and other structures along the path of the rover and test the hypothesis about geomorphological signatures of permafrost in the lunar polar areas. If a relationship between characteristics of lunar craters and the distribution of permafrost is confirmed, this will open a possibility to remotely determine the deposits of lunar ice from satellite imagery.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/900187

2022059926 Grebenets, Valery I. (Lomonosov Moscow State University, Moscow, Russian Federation). Methods of maintenance of stability of engineering infrastructure in Eurasian cryolithozone [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55E-0478, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

During the last decades, the problem of stability of buildings and constructions in permafrost zone has been significantly aggravated. In the cities of the Northern Russia, the tendency toward the development of total deformation of constructions has been appeared. Thus, in Khatanga, Vorkuta, Igarka, over 50% of buildings and constructions were deformed. In Norilsk, the largest Trans-Polar industrial center, about 40% of buildings were deformed and 50 ones of 5-10--stored and 10-40 years old are highly emergent and have to be teared down. In has been found that the activity of dangerous cryogenic processes is increasing. The main reasons of deformations are negative technogenic effect on the geocryological and geoecological environment, while the global climate warming still does not affect on the bearing capacity of frozen bases. The complex of engineering measures for the stabilization of the situation in important centers of the Northern Russia as well as specific methods of strengthening of frozen bases has been worked out and experimentally tested. The major measures are: 1) application of artificial cooling of grounds through the use of liquid and vapor-liquid; 2) the cementation of local talics, statical pressing of piles; 3) use of wide range of methods of prevention of consequences of dangerous cryogenic processes. Among the measures of managing of geocryological situation in large urban territories, new techniques for laying of underground collectors for engineering communications have been used, as well as additional cooling of underground communications, increasing of ventilation of cold bases, devising of counterfiltration screens in technogenic embankments, regulation of the snow cover regime in built up areas, organization of the run-off of rain and flood water, management of waste, etc. This work was supported by the RFBR project 18-05-60080 "Dangerous nival-glacial and cryogenic processes and their impact on the infrastructure in the Arctic".

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/856758

2022059935 Grewal, Arsh (McMaster University, School of Earth, Environment & Society, Hamilton, ON, Canada); Nicholls, Erin M. and Carey, Sean. The influence of shrub expansion, frozen ground, and seasonality on diurnal patterns of stream discharge and chemistry in a subarctic headwater catchment, Yukon, Canada [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H14E-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Diurnal patterns in radiation, discharge, water temperature, and stream chemistry are ubiquitous in freshwater ecosystems. Diurnal patterns in flow and chemistry respond to radiation fluxes, antecedent moisture, and the physical properties of the contributing area. Consequently, changes in diurnal patterns can be used to infer changes in watershed structure and function and inform processes of water storage and hydrologic connectivity. Throughout circumpolar regions, warming has accelerated permafrost thaw, lengthened the growing season, and expanded shrub ecosystems; all of which influence hydrological and biogeochemical processes. In this study, we use long-term hydro-chemical data from Granger Creek, a well-studied and rapidly changing headwater basin within the Wolf Creek Research Basin in Yukon Territory, Canada to evaluate drivers of diurnal stream fluxes and assess the influence of frozen ground and shrub expansion that have occurred through time. Additionally, we examine the role of seasonality on catchment function by analyzing the influence of energy fluxes and plant water use on diurnal patterns of discharge, conductivity, pH, and colored Dissolved Organic Matter (cDOM). Results show a strong relationship between incoming solar radiation and diurnal streamflow, with a positive relationship during June, where diurnal streamflow is primarily driven by snowmelt, and a negative relationship from late July to the end of September, where diurnal streamflow is primarily driven by evapotranspiration (ET). Significant increases in amplitude of discharge for snow free months were also detected over a 10-year period. The rate of change of flow corresponded more closely to solar peaks during July and August than September. These results suggest shrubification and changes in seasonal ET processes can be detected through changes in the diurnal stream pattern. Diurnal timing of minimum concentrations of cDOM was close to solar peak during both ET and snowmelt dominant periods, showing evidence of photodegradation of cDOM as the dominant process in Granger Creek during summer baseflow.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/988062

2022056013 Griffin, Claire (University of Virginia, Charlottesville, VA); Kent, Kelcy; Epstein, Howard E. and Liljedahl, Anna. Effects of watershed position, landscape connectivity, and ice wedge degradation on dissolved organic matter dynamics at Prudhoe Bay, AK [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1749, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Degradation of ice-wedge polygons in Arctic landscapes can lead to dramatic, interconnected changes in both the physical environment and biogeochemical cycling. As ice wedges thaw, poorly drained, low-centered polygons transform into well-drained high-centered polygons, surrounded by connected water-filled troughs. As permafrost thaws and landscape connectivity increases, dissolved organic matter (DOM) may be mobilized, resulting in changes in the amount and composition of DOM lateral transfer, and potentially increased remineralization. As yet, it is poorly understood how the connectivity of ice-wedge polygon landscapes contributes to in situ losses of DOM and the lateral movement of DOM through a watershed. We collected water samples from surface water and porewaters along a gradient of ice wedge degradation and from a field-mapped flowpath near Prudhoe Bay, Alaska, in July 2019. The field data was complemented by a hydrological model based on the WAter flow and balance SImulation Model (WaSiM), to gain a high-resolution, accurate assessment of hydrological flow throughout the landscape. Our goal is to understand the interactions between watershed position and ice wedge degradation in controlling the transport and transformations of DOM. We measured dissolved organic carbon (DOC), chromophoric dissolved organic matter (CDOM), dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON) at each site. Previous work has established clear signs of degradation and stabilization in the study area, through repeat aerial imagery, high-resolution GPS data, and soil cores, resulting in increased water connectivity over the past fifty years. DOC concentrations were lowest at the outlet, and increased going upstream along the flowpath. There was no difference in either DOC concentration or DOM composition between troughs and ponds, indicating the importance of connectivity. The clearest differentiation between site types was based on pore versus soil water samples, with highest DOC, DON, and DIN at sites closer to the soil-water interface.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/998788

2022059986 Guillemot, Antoine (ISTerre Institute of Earth Sciences, Saint Martin d'Heres, France); Baillet, Laurent; Larose, Eric; Helmstetter, Agnes; Bodin, Xavier and Mayoraz, Raphael. Seismic monitoring of rock glaciers; new insights on observations and modelling permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract S53A-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Rock glaciers are mountain permafrost landforms composed of a heterogeneous mixture of rock debris, ice and liquid water. They can reach surface velocities of several m/yr for the most active ones, and can therefore cause an emerging risk that needs to be monitored. Several geophysical methods (radar, seismic refraction, geoelectrics) provide interesting tools for investigating the subsurface, while in-situ and remote sensing methods make it possible to follow the kinematics of these study objects. However, all these methods do not offer sufficient temporal resolution for continuous monitoring at depth.Passive seismic instrumentation can overcome this difficulty by providing continuous ambient noise and microseismicity data. Such instrumentation has been deployed for several years at Gugla (Valais, Switzerland) and Laurichard (Hautes-Alpes, France) rock glaciers.From these data, Coda Wave Interferometry and spectral analysis of seismic ambient noise provide daily observables (relative change velocity of the surface waves, and resonance frequencies of the glacier's vibration modes) which are directly linked to the elastic properties of the medium at depth, and therefore its rigidity and density.For the two sites studied, the seasonal variations of these observables show a cyclic freeze-thawing effect on the mechanical properties of the medium subjected to seasonal hydro-thermal forcing. Mechanical modelling using a poroelastic approach was built to quantify the effect of seasonal freezing on the global stiffening into the medium at depth, and on the measured seismological observables. A simple viscoelastic model can also be used to explain the seasonal variability of the deformation rate of rock glaciers. In the long term, analyzing the multiannual trend in seismological parameters could help to detect changes in ice content and thus quantify the permafrost degradation.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/936781

2022057045 Guimond, Julia (Dalhousie University, Department of Civil and Resource Engineering, Halifax, NS, Canada); Mohammed, Aaron; Walvoord, Michelle A.; Bense, Victor and Kurylyk, Barret. Feedbacks between sea-level rise, groundwater flow, and permafrost extent in the coastal zone [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In some Arctic regions, sea-level rise (SLR) is driving coastal erosion and inundation. In the subsurface, SLR also drives the landward migration of the freshwater-saltwater interface, but the impacts of saltwater intrusion on permafrost-bound coastlines are unclear. To date, sparse field data and the absence of numerical models that can simulate complex salinity-dependent processes in the coastal zone have hampered present understanding of coastal subsurface dynamics. In this study, we build on previously developed cold-regions groundwater numerical models through incorporation of salinity-dependent freeze-thaw with solute exclusion and variable-density fluid flow. Using this newly developed model, we investigate SLR coupled to land and ocean warming impacts on coastal ice-rich permafrost extent. Results suggest that SLR drives lateral thaw due to the intrusion of saltwater into unfrozen pore space and subsequent depression in freezing temperature. Warming of the ocean and land surface drives top-down thaw, and thus the combination of SLR and warming result in extensive coastal ice-rich permafrost loss. Under high SLR and low warming scenarios, thaw driven by SLR can exceed warming-driven thaw when normalized to the surface area influenced. This study highlights an overlooked feedback mechanism between SLR and permafrost thaw with potential implications for coastal stability and infrastructure, carbon mobilization, and groundwater and solute discharge to the coastal ocean.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/823226

2022057026 Guo, Hong (University of Arkansas, Fayetteville, AR) and Feng, Song. Detection and attribution of active layer changes in the Northern Hemisphere [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35D-0911, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Due to rapid warming in the cold regions, massive permafrost destruction has been documented in recent decades. Given the significant consequences of permafrost change, it's essential to consider the causes of active layer thickness (ALT) deepening. The use of detection and attribution analysis to explore the contributions of multiple factors to observed climate changes is a novel method. The Stefan equation and the air temperature from the Climatic Research Unit (CRU) were used to estimate observational ALT and validate the CESM simulations. To assess the relative contributions of internal and external variability on permafrost change in the Northern Hemisphere during the timespan 1921-2100, model outputs from the Community Earth System Model Large Ensemble (CESM-LENS) and Observational Large Ensembles (OBS-LENS) were employed in this study. To examine the relative contribution of internal climatic variability or forced signals, the signal-to-noise ratio (SNR, the ratio of external forcings to internal climatic fluctuation) was also adopted. In both CRU observational data and CESM simulations, the results demonstrate a considerable increase in ALT. External forcing has a large warming influence in the Northern Hemisphere, but internal variability has resulted in cooling in some high-latitude areas. We also discovered that the SNR in the CESM simulations may be underestimated. Between 1921 and 2005, our study reveals that anthropogenic factors are the primary driver of observed permafrost deterioration around the south limit of the permafrost zones, while internal climate variability dominates driven changes in other places. Anthropogenic forcing has grown more important than internal variability since 2005.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/956178

2022057039 Haagenson, Ryan (Johns Hopkins University, Baltimore, MD); Rajaram, Harihar; Kansara, Prakrut O.; Kim, Kyung Yoon and Lakshmi, Venkataraman. Assessing permafrost behavior in high mountain Asia with physics-based models [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0939, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Though permafrost plays a significant role in the hydrologic systems of mountainous terrain, observations of subsurface thermal conditions and the occurrence of frozen ground in high mountain Asia are sparse. Hence, methods other than in-situ measurement for estimating the extent of permafrost in this remote region is required. In contrast to previous studies based on empirical relationships, we attempt to understand the extent and behavior of permafrost in high mountain Asia through high-fidelity, physics-based modeling. The goal is to constrain variables such as ground temperature profiles, permafrost depth, and active layer dynamics across the region based on the best available meteo-hydrologic forcing datasets and subsurface characterizations. Through this approach, we hope to gain insight into the physical phenomena that control permafrost dynamics in the highly variable conditions of high mountain Asia. For example, differences in snowpack depth and timing between the western regions (e.g. Pamir and Hindu Kush ranges) and the central or eastern Himalayas (where precipitation is dominated by the seasonal monsoon cycle) may lead to drastically different behavior in permafrost dynamics as the ground is insulated from air temperatures and solar radiation during different times of the year. Moreover, strong spatial variations in cloud coverage are likely to influence the incoming solar radiation to the ground surface, altering the ground surface energy exchange and thermal state of the subsurface. These unique climatological features of high mountain Asia, combined with the typical complexities of modeling permafrost in mountainous terrain, create a challenging task.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/966603

2022056017 Halas, Agnieszka (Polish Academy of Sciences, Institute of Geography, Warsaw, Poland); Lamentowicz, Mariusz; Lucow, Dominika; Loiko, Sergey; Konstantinov, Alexandr; Krickov, Ivan V. and Slowinski, Michal M. A new local testate amoebae transfer function from northwest Siberian permafrost peatlands [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1753, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Testate amoebae (TA) transfer functions have been used in palaeoecological studies for more than 30 years. Several widely used transfer functions are available; however, studies have shown that the performance of the transfer function declines if it is applied outside the area of its development. This observation and the increasing use of TA in research conducted on a wide range of peatlands in Asia have resulted in a recently constructed Asian data set. However, this continental-scale training set does not include data from newly collected Sphagnum-dominated northwest (NW) Siberian peatlands. Because of the presence of permafrost and ongoing thawing processes, this specific mosaic ecosystem creates unique living conditions for microorganisms (e.g., TA). Therefore, to decode the history of this area more accurately the local transfer function is needed. Our aim was to make a new local transfer function based on surface samples from peatland collected in the irregular permafrost area - Khanymey region (NW Siberia, Russia). A total of 76 surface samples were collected from location along microtopographic gradient of peatlands, including hummocks, hollows, lawns and pools. For TA analysis, the upper 5 cm of growth of Sphagnum spp., brown mosses, and Cladonia sp. were collected. During the sampling the DWT or permafrost (when water table was not present) was measured. The collected samples represented the moisture gradient from +38 cm (terrestrial habitat) to -20 cm (inundated surface) including the permafrost area. In each sample, 150 shells were counted. TA was identified using a consensus taxonomic framework, which led to the creation of a list of TA from NW Siberian permafrost peatlands. We also developed new local TA-based hydrological transfer functions using software C2. We noted that the occurrence and properties of the active layer creates significantly different moisture conditions for TA, leading to changes in TA composition. Contrastingly, some inundated habitats (including associated TA communities) might occur due to permafrost thawing as an effect of the global warming. We plan to use the new transfer function in the analysis of a core collected from the same area. The study was supported by the National Science Center (Grant no. 2019/35/O/ST10/0290) and INTERACT No. 730938 - PeatHOT project.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/930037

2022057066 Hasan, Amit (University of Connecticut, Department of Natural Resources and the Environment, Groton, CT); Udawalpola, Mahendra; Liljedahl, Anna K. and Witharana, Chandi. Understanding the effect of image augmentation methods on automated recognition of permafrost features from high-resolution satellite imagery [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Commercial satellite sensors offer the luxury of 'sub-meter view' for the entire Arctic. Big imagery repositories position the permafrost science at the precipice of revolution. We ideally gain the imagery-enabled power to map, monitor, and document individual permafrost features and their change over time. When confronted with hundreds-to-thousands of imagery, manual interpretations and conventional image classification methods show little success except for site-/local scale analysis. Artificial intelligence (AI) methods, especially deep learning (DL) convolutional neural nets (CNNs), demonstrate a remarkable success in automated analysis of semantically complex imagery in multiple domains. By design, inferential strengths of CNN models are primarily driven by the quality and volume of training data. Production of hand-annotated samples is a time-, labor-, and knowledge-intense process. This is particularly true for regional-scale mapping applications, such as permafrost feature detection across the Arctic, where landscape complexity would spontaneously inflate the semantic complexity of sub-meter resolution imagery. Additionally, image dimensions, multispectral channels, imaging conditions, seasonality, coupled with multiscale organization of geo-objects pose extra challenges on the generalizability of DLCNN models. Image augmentation is a strategic 'data-space' solution to synthetically inflate the size and quality of training samples without additional investments on hand-annotations. A plethora of augmentation methods have been proposed under the auspices of two general categories: data warping and oversampling. The performances of image augmentations methods largely depend on the image recognition problem in hand and characteristics of underlying data. In this study, we systematically investigate the effectiveness of a series of augmentation methods, such as color space and feature space augmentation, geometrical transformations, random erasing, and kernel filter when applied to CNN algorithms to automatically recognize ice-wedge polygons from commercial satellite imagery.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/953703

2022057038 Hassan, Javed (China-Pakistan Joint Research Center on Earth Sciences, Pakistan); Chen Xiaoqing; Sher, Muhammad and Bazai, Nazir Ahmed. Rock glacier inventory, permafrost probability distribution modeling and associated hazards in the Hunza River basin, western Karakoram, Pakistan [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0938, illus. incl. sketch maps, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The destabilization of rock glaciers and permafrost variations is of great importance to the safety of the population and infrastructure in the Karakoram region because of their effects on land stability and river obstructions. In this study, we compiled the first complete rock glacier inventory for the Hunza Basin, western Karakoram, of 616 rock glaciers with an area of 194 km2 between 2800 and 5700 m a.s.l. We categorized the rock glaciers as intact or relict, and their distributions and destabilization were further analyzed and used along with in situ climate and elevation dataset to model the permafrost probability distribution. The modeled areas where the permafrost zonation index (PZI) is 0.5-1.00 indicate that permafrost occurs over 85% of the catchment area and lies above 3525 m a.s.l., which closely matches the zero-degree isotherm of 3800 m a.s.l. Based on the sensitivity analysis of the independent variables, elevation is the most sensitive variable, followed by net radiation, for predicting the probabilities of the presence and absence of permafrost. The model distributions are quite precise, with median posterior areas under the curve of 0.98 and 0.96 for model training and testing, respectively. We analyzed the rock glacier destabilization for 68 rock glaciers that interacted with river channels, of which 50 blocked or diverted river channels. Destabilized rock glaciers can be closely linked to the 0°C isotherm between 3400 and 4600 m a.s.l. The significant damage caused by periodic floods from the subsequent blockage of river channels by landslides can be attributed to variations in permafrost which demolished infrastructure, including a hydropower plant, suspension bridge and water supply system in Hassan-abad catchment. Quantification of rock glacier dynamics and permafrost in the region can further improve policies related to the reduction in disaster risk and mitigation of associated hazards.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/934763

2022055993 Heffernan, Elise (University of Virginia, Charlottesville, VA); Armstrong, Amanda Hildt; Epstein, Howard E.; Montesano, Paul; Osmanoglu, Batuhan; Ranson, Kenneth and Shugart, Herman Henry. Assessing Canadian boreal forest-tundra growth drivers via community analysis [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31A-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The primary vegetation growth drivers at the Arctic treeline vary among locations, leading to a heterogeneous response of treeline advance, infill, and retreat. Using National Forest Inventory (NFI) data and remotely sensed vegetation data, we analyzed plant species distribution from 134 plots from the Northwest Territories, Canada, using nonmetric multidimensional scaling (NMDS) to assess which environmental factors may be most indicative of treeline response to climate change. The environmental variables used in our analysis included field plot data from the NFI along with remotely sensed indices (treeline ecotone plant density, NDVI change over time, and percent cover shifts from broadleaf to coniferous species). By combining field and remote sensing data, we were able to match dynamic vegetation changes observed from satellite sensors with more localized plot and soil characteristics. Initial assessments of plant species distribution showed latitude and live tree biomass were highly correlated with axes 1 and 2 of the NMDS, while elevation and depth to permafrost were correlated with axis 3. By assessing the entire species distribution (not just tree and shrub species), we were able to investigate how non-target species might be representative of complex processes. The indicator species analysis used ecotone clusters to determine species significance and found the presence of shrubs, moss, and lichen to be more indicative of the different ecotone clusters than any tree species. Examining fine spatial resolution field data with dynamic, coarser satellite data enabled us to identify potential drivers of tree growth across the boreal forest-tundra ecotone.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/970064

2022055978 Heim, Birgit (Alfred Wegener Institute Helmholtz-Center for Polar, Marine Research Potsdam, Polar Terrestrial Environmental Systems, Potsdam, Germany); Shevtsova, Iuliia; Buchwal, Agata; Rachlewicz, Grzegorz; Lisovski, Simeon; Runge, Alexandra; Fuchs, Matthias; Grosse, Guido; Kruse, Stefan; Herzschuh, Ulrike and Bartsch, Annett. Above ground biomass stocks, pool ages and fluxes in the largest Arctic delta, the Lena Delta in Siberia [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B22D-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Vegetation biomass is a globally important climate-relevant terrestrial carbon pool. Landsat, Sentinel-2 and Sentinel-1 satellite missions provide a landscape-level opportunity to upscale tundra vegetation communities and biomass in high latitude terrestrial environments.We assessed the applicability of landscape-level remote sensing for the low Arctic Lena Delta region in Northern Yakutia, Siberia, Russia. The Lena Delta is the largest delta in the Arctic and is located North of the treeline and the 10 °C July isotherm at 72° Northern Latitude in the Laptev Sea region.During the LENA2018 expedition, we set up plots for plant projective cover and Above Ground Biomass (AGB) and sampled shrubs for shrub-ring analyses. AGB is providing the magnitude of the carbon flux, whereas stand age is irreplaceable to provide the cycle rate. AGB data and shrub age data clearly show a separation between i) low disturbance landscape types with dominant AGB moss contribution, but always low vascular plant AGB (-2) characterised by old shrubs of several decades of stand age versus ii) a much higher vascular plant AGB contribution (> 0.5 kg m-2) with only young shrubs in high disturbance regimes. The low disturbance regimes are represented on the Holocene and Pleistocene delta terraces in form of azonal polygonal tundra complexes and softly dissected valleys with zonal tussock tundra. In contrast, the high disturbance regimes are sites of thermo-erosion such as along thermo-erosional valleys and on floodplains. We upscaled AGB and above ground carbon pool ages using a Sentinel-2 satellite acquisition from early August 2018. We classified via classification training using Elementary Sampling Units that are the 30 m x 30 m vegetation field plots. We then used the land cover classes and grouped them according to their settings either in high disturbance or low disturbance regimes with each associated AGB value ranges and shrub age regimes. We also evaluated circum-Arctic harmonized ESA GlobPermafrost land cover and vegetation height remote sensing products covering subarctic to Arctic land cover types for the central Lena Delta. The products are freely available and published in the PANGAEA data repository under URL: https://doi.org/10.1594/PANGAEA.897916, and URL: https://doi.org/10.1594/PANGAEA.897045. ESA GlobPermafrost land cover and vegetation height remote sensing products and our Sentinel-2 derived AGB product for the central Lena Delta shows realistic spatial patterns of landcover classes and biomass distribution at landscape level. However, in all products, the high biomass patches of high shrubs in the tundra landscape could not spatially be resolved as they are confined to patchy and linear distribution, not representing large enough areas suitable for upscaling. We found that high disturbance regimes with linked high and rapid AGB fluxes are distributed mainly on the floodplains and as patches along thermoerosioal features, e.g. valleys. Whereas the low disturbance landscapes on Yedoma upland tundra and Holocene terraces occur with larger area coverage representing decades slower and in magnitude smaller AGB fluxes.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/879218

2022055989 Hessilt, Thomas Duchnik (Vrije Universiteit Amsterdam, Amsterdam, Netherlands); Abatzoglou, John; Chen, Yang; Randerson, James Tremper; Scholten, Rebecca; van der Werf, Guido and Veraverbeke, Sander. Future increases in lightning-ignited boreal fires driven by joint increases in dry fuels and lightning [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24E-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Fire is the most important landscape disturbance in the boreal forest of North America. Burned area has increased over much of the boreal region in the last decades, and approximately 90% of the burned area originates from lightning-induced fires. Lightning density in the Northwest of the North American boreal forest is predicted to increase with 76 ± 20% by end-of-century compared to present day based on different model estimates. This may increase the number of lightning ignitions and result in further increases in burned area. It is essential to understand the drivers of these lightning-induced fires to evaluate the consequences of future changes in lightning density and ignition efficiency. We assessed the lightning ignition efficiency i.e. the probability that a lightning strike starts a fire, for Alaska and the Northwest Territories between 2001 and 2018 in function of lightning characteristics, topography and fire weather. We combined predictions of future lightning activity and fire weather using a high emissions scenario (representative concentration pathway 8.5) to project future lightning ignition efficiency and ignitions. Fire weather was a strong predictor of lightning ignition efficiency in our logistic regression model (area under the curve > 0.83), whereas the lightning characteristics and topography showed little contribution to the model performance. The short-term drying of fuels was the most important variable for lightning-induced fire, and, under a warming scenario, increased drying would result in lightning ignition efficiency increases of 10 ± 6% and 13 ± 8% per 1 degree Celsius increase for Alaska and the Northwest Territories. Combined with future projections of lightning activity, we predicted an increase in lightning ignition of up to 53 ± 6% and 52 ± 10% per 1 degree Celsius increase for Alaska and the Northwest Territories by 2100. In addition to predicted increases in lightning, this amounts to two-fold increases in lightning ignitions. These additional ignitions will likely lead to additional burned area in carbon-rich forested peatlands underlain by permafrost. Our research shows that increases in the availability of dry fuels and lightning density over the boreal region will reinforce each other and lead to more boreal fires and consequent carbon emissions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/900179

2022057030 Hinzman, Alexa (Vrije Universiteit Amsterdam, Amsterdam, Netherlands); Schaap, Peter; Sjoberg, Ylva; Lyon, Steve W. and van der Velde, Ype. Potential influences of rising non-linearity in catchment storage-discharge relationships as the extent of frozen ground decreases [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0930, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The relationship between groundwater and stream discharge in Arctic and sub-Arctic regions is strongly controlled by permafrost. Previous work has shown that Arctic catchments with thawing frozen soils due to the warming climate are expected to show changes in the storage-discharge relationship. Specifically, greater influence of some controlling factors on the storage discharge relationship emerge as new flow paths open. With this study, we use a mechanistic modelling approach to demonstrate that the actual effect of permafrost thaw, conceptualized as the reduction of an impermeable layer in the subsurface, will likely only be clearly visible in the change in the recession curve as the soils thaw for catchments with hillslope gradients greater than 1%. For flat catchments (1% hillslope gradient), the recession curve slope signal will likely be dominated by active layer parameters, such as changes in shallow surface permeability and shallow surface & subsurface water retention. Moderately sloped Arctic catchments (5% and 10% hillslope gradients) suggest the recession curve slope signal is dominated by changes in the domain length and subsurface hydraulic properties, with minimal impact from overland flow properties and changes in meteorological factors. Several parameters are more likely than others to evolve with the ongoing Arctic climate change. These findings are based on an analysis of stream flow recessions. It is a step forward in the interpretation of recession curve slopes for the Arctic, which provides insight on the hydraulic parameters that are causing the increasing non-linearity in the storage discharge relationship.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/964511

2022057047 Hosekova, Lucia (University of Washington, Applied Physics Laboratory, Seattle, WA); Thomson, Jim; Eidam, Emily and Rainville, Luc. Coastal wave exposure in northern Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Alaskan coastlines are exposed to increasing wave activity linked to sea ice retreat. Waves and storm surges are among leading environmental drivers of coastal erosion due to their ability to suspend and remove sediment. These mechanical processes can exacerbate thermal processes (i.e., notching the toe of permafrost bluffs).We use field measurements from three coastal sites in the Beaufort and Chukchi Seas collected over a seasonal cycle to quantify coastal wave exposure and the dissipative role of nearshore ice. The dataset highlights differences between wave-ice interactions during melt and freeze-up seasons. During spring sea ice retreat, the persistent landfast ice resulted in complete attenuation of incident waves and this caused significant delays in wave onset near the coast. In contrast, during the autumn ice advance the waves were only partially attenuated in newly forming pancake and frazil ice. This is relevant to studies using global reanalysis products to assess the effects of waves on coastal erosion. Local ice conditions, in particular the presence of landfast ice, are generally not represented in global reanalysis datasets and can lead to biases in estimated incident wave energy. The biases are particularly severe for long term trends. We quantify coastal wave exposure using several metrics and compare our observations to ERA5 reanalysis. We find that unresolved landfast ice causes ERA5 to overestimate the total spring wave exposure near the Chukchi coast by up to 47%, and propose a method to correct this bias. Supported by the National Science Foundation and Office of Naval Research.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/912074

2022057037 Hu Yan (Chinese University of Hong Kong, Hong Kong, China); Liu Lin; Huang Lingcao; Zhao Lin and Wu Tonghua. Inventorying rock glaciers in the arid West Kunlun of China using SAR interferometry and deep learning [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0937, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Rock glaciers manifest the creep of mountain permafrost occurring in the past or at present. Their presence and dynamics are important indicators of permafrost distribution and changes in response to climate forcing. However, knowledge of rock glaciers is completely lacking in the West Kunlun, one of the driest mountain ranges in Asia, where widespread permafrost is rapidly warming. In this study, we first mapped and quantified the kinematics of active rock glaciers based on satellite Interferometric Synthetic Aperture Radar (InSAR) and Google Earth images. Then we trained DeepLabv3+, a deep learning network for semantic image segmentation, to automate the mapping task. The well-trained model was applied for a region-wide, extensive delineation of rock glaciers from Sentinel-2 images to inventory the landforms that were previously missed in the InSAR-based identification. Finally, we inventoried 413 rock glaciers across the West Kunlun: 290 of them were active rock glaciers mapped manually based on InSAR and 123 of them were newly outlined by deep learning. The inventory also classifies the rock glaciers by their spatial connection to the upslope units into four types, namely the glacier-connected (total number: 202), the debris-mantled slope-connected (143), the glacier forefield-connected (41), and the talus-connected (27). All the rock glaciers are located at altitudes between 3389 m and 5541 m with an average size of 2600 m2 and a mean slope angle of 17°. The mean and maximum surface downslope velocities of the active ones are 0.24 m yr-1 and 1.27 m yr-1, respectively. Characteristics of the inventoried rock glaciers hold implications on the interactions between glacial and periglacial processes in the West Kunlun. The method of combining InSAR and deep learning proves to be effective for compiling rock glacier inventories with kinematic information over a significant extent of cold regions, e.g., the Tibetan Plateau, which provides a baseline dataset and allows the monitoring of rock glaciers as indicators of permafrost state and potential water sources in a changing climate.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/922785

2022056002 Humphreys, Elyn (Carleton University, Ottawa, ON, Canada); Bieniada, Aneta and Todd, Aaron. An analysis of methane emissions from four peatland sites in the Hudson Bay Lowlands [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B32E-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

We present eddy covariance measurements of ecosystem scale methane (CH4) emissions at four peatland sites in the Canadian Hudson Bay Lowlands (HBL). The study sites vary widely in vegetation, hydrology, and soil thermal characteristics and their potential environmental response to climate change. Two study sites are in a region of permafrost in Polar Bear Provincial Park, about 30 km inland of Hudson Bay. Climate warming is expected to convert drier peat plateau underlain by permafrost (site: CA-PB1) to wetter, sedge-dominated peatlands (site: CA-PB2) and may enhance methane emissions. About 250 km to the south, the two study sites include a treed bog (CA-ARB) and treed fen (CA-ARF) where climate warming may result in drier peat in summer and potentially reduce methane emissions. For simplicity, we call the sites PB1, PB2, ARB, and ARF, respectively. Fluxes were measured between April and November for 6, 7, 2 and 1 seasons at ARB, ARF, PB2, and PB1, respectively. At daily to monthly time steps, Tsoil was the main driver of temporal variations in CH4 fluxes. However, the Tsoil measurement that explained the most variation in daily CH4 emissions was not from the same depth within the peat profile for any of the sites. This suggests that the different soil thermal characteristics and rates of methane production/consumption, storage, and transport processes impact temporal variations in methane emissions differently at the four sites. Methane emissions were sensitive to VWC at the end of summer at ARB and ARF. Total seasonal CH4 emissions also varied with soil moisture status among sites. Emissions were greatest at the wettest site, ARF (4.8 - 7.2 g m-2 season-1), followed by PB2 (3.7 - 4.5 g m-2 season-1), ARB (3.0 - 4.5 g m-2 season-1), and PB1 (1.7 g m-2 season-1), the driest site. This research highlights the variability in methane emissions in diverse northern peatlands and can inform the modelling and inventory of current and future peatland methane emissions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/919139

2022056016 Hung, Jacqueline (Woodwell Climate Research Center, Falmouth, MA); Treitz, Paul and Scott, Neal A. Soil moisture inputs from enhanced snowfall impact nitrogen availability and the greenhouse gas balance of High Arctic mesic tundra [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1752, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic warming and changing precipitation regimes are altering nutrient availability and processes that control the greenhouse gas balance of high latitude ecosystems. Climate warming is expected to increase Arctic winter precipitation, and models show that Arctic precipitation may become rainfall dominated. Changes to biogeochemical processes as a result of climate change and altered moisture regimes will ultimately determine whether the Arctic will enhance or dampen future climate feedbacks. At the Cape Bounty Arctic Watershed Observatory, a full factorial International Tundra Experiment site was established in 2008, allowing for the investigation of ten years of experimental warming and increased snowfall on nutrient availability and greenhouse gas release in this mesic heath tundra across two growing seasons (2017 and 2018). Ambient snowfall conditions had deeper thaw depths than those under enhanced snow conditions, and differences in thaw depth across experimental treatments decreased as the growing season progressed, driven by rainfall. Seasonal and interannual variability in nitrogen availability, carbon dioxide release, and nitrous oxide fluxes were driven by elevated late season rainfall in 2018. While experimental warming decreased soil moisture and ammonium availability and increased CO2 release, these effects were enhanced under wetter conditions. Coupled interactions of enhanced snow and experimental warming also increased nitrate availability, and this corresponded with increased N2O release. Together, results from this study suggest that the greenhouse gas balance of High Arctic environments is closely tied to the interaction between soil moisture and nitrogen availability, which will be moderated by future shifts and interactions between climate variability and ecological responses to permafrost thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/977920

2022057024 Irrgang, Anna M. (Alfred Wegener Institute Helmholtz, Center for Polar and Marine Research, Potsdam, Germany); Jones, Benjamin M.; Farquharson, Louise Melanie; Baranskaya, Alisa; Belova, Nataliya; Bendixen, Mette; Boisson, Antoine; Forbes, Donald L.; Freitas, Pedro Antonio Faria; Gibbs, Ann; Günther, Frank; Jaskolski, Marek W.; Kokin, Osip; Kroon, Aart; Manson, Gavin K.; Maslakov, Alexey; Novikova, Anna V.; Ogorodov, Stanislav A.; Overduin, Paul; O'Rourke, Michael; Strzelecki, Matt C.; Tweedie, Craig E.; Veremeeva, Alexandra; Vieira, Goncalo; Whalen, Dustin and Lantuit, Hugues. News from the pan-Arctic initiative on the spatial and temporal dynamics of Arctic coasts [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C25F-0884, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic coasts are a hotspot for rapid landscape change - coasts made up of ice-rich permafrost which are exposed to high wave energy can retreat over 30 m per year, even though sea ice limits erosion to three to four months per year. Climate warming intensifies environmental factors that govern shoreline changes, for example rising air and water temperatures, increasing wave energy and growing sea level. Thus, with ongoing climate warming, more dynamic and in particular more rapidly eroding shorelines are to be expected. The Arctic coastal zone also provides a hub for human activities; almost half of all Arctic permafrost residents are living in coastal settlements, and the Arctic coastal population is projected to increase in the coming decades. These two developments of accelerating shoreline retreat and human migration bring to a head the issue of quantifying and analyzing present shoreline change rates in order to create a reliable database that will enable us to build projections for future shoreline changes and provide a foundation for sound management choices. In a joint effort of the EU project NUNATARYUK and the NSF project PerCS-Net, we seek to build this foundation by collecting and analyzing all accessible high-resolution shoreline position data for the Arctic. With our database structured to be open for new data submissions, we processed all available data from the Russian, Svalbard and the Canadian Arctic coast that reached us by the end of July 2021. We used the Esri ArcGIS DSAS (Digital Shoreline Analysis System) extension tool to calculate shoreline change statistics. First results show us that despite some natural variability, which is particularly high over short time-period analyses, shorelines are tending towards more rapid shoreline retreat in numerous places across all three regions. The data will contribute to an updated version of the ACD database, which pursues the long-term goal of providing a comprehensive collection of standardized and ready-to-use shoreline change data for the Arctic coast.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/933920

2022059927 Iurov, Fedor (Lomonosov Moscow State University, Moscow, Russian Federation). Risks of stability of transport systems in the western sector of the cryolithozone of Russia with the development of dangerous cryogenic processes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55E-0479, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The western sector of the Russian Arctic is a promising and quite actively developing region, which is due to its importance for the fuel and energy complex of Russia and Western Europe. For the stable functioning of the region, it is necessary to create and ensure the stability of an extensive network of transport infrastructure. n permafrost-geological terms, the studied region has an extremely heterogeneous structure. The permafrost thickness and its distribution (from isolated patches to continuous), the depth of seasonal thawing, ice content and other parameters vary a lot. Beyond that, the region is heterogeneous in terms of terrain, there are parts of mountain and lowland permafrost. The most dangerous groups of cryogenic processes for the linear infrastructure were selected: frost cracking, icing, frost heaving, slope processes, thermal erosion and thermal abrasion of the shores, thermokarst. The risk assessment was carried out according to three main indicators: the degree of affection by the cryogenic process of the territory of the laying of transport routes, the duration of exposure and the probability of their activisation. The product of these indicators allowed us to obtain a relative degree of risk from the effects of cryogenic processes. Studies have shown that the complex of cryogenic processes that are dangerous for the transport infrastructure is directly related to the landscape-permafrost and engineering-geological conditions of the territory. For example, thermokarst is the most dangerous for linear objects in the northern part of the Yamal Peninsula, where highly ice rich soils are common. There, the risk level is estimated at 0.08 (high risk), while in foothill areas where rocks lie close to the surface (for example, in the area of the village of Harp), this indicator is only 0.0006. In turn, in the area of the Polar Ural, the danger to the linear infrastructure is extremely high with the activisation of slope processes (0.003 for the settlements of Harp and Yeletsky), while in the flat territories (Tarko-Sale, Labytnangi, Novy Urengoy, etc.), the risk index for the activation of cryogenic landslides and kurums is actually 0. This work was supported by the RFBR grant 20-35-90009 "Features of the impact of hazardous cryogenic processes on the transport infrastructure of the Arctic region"

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/963748

2022057064 Iwahana, Go (University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK); Busey, Robert; Muskett, Reginald R.; Zwieback, Simon; Meyer, Franz Josef; Ohno, Hiroshi; Uchida, Masao and Saito, Kazuyuki. Fine-scale ground truth of ground displacement in the Anaktuvuk River fire (ARF) for satellite and airborne L-band SAR [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Spatial variations in inter-annual and seasonal ground displacements are essential information to estimate the rate of permafrost degradation. The differential SAR interferometry (DInSAR) has been deployed in permafrost regions to evaluate freeze/thaw-related ground surface displacement. However, the interpretation of the DInSAR results over permafrost terrains was often performed without detailed knowledge about ground surface conditions. To better understand the nature of DInSAR signals over changing permafrost lands, we investigated surface displacement caused by frozen ground dynamics and thermokarst development triggered by a tundra wildfire in Alaska. The Anaktuvuk River Fire (ARF) combusted surface vegetation and organic mat of the tundra region underlain by variously ice-rich permafrost in 2002. High-precision GNSS survey, thaw depth, and surface moisture were measured along 60-200 m transects at three representative sites in ARF during snow-free seasons in 2017-2019. The three sites were located in the northernmost fire boundary, the central area, and the southernmost of the ARF burn scar underlain by differently ice-rich permafrost. High-resolution (~1 m) DInSAR signals by UAVSAR depicted enhanced seasonal thaw settlement not only in the burned area but also a liner pattern development of larger subsidence in unburned areas, which coincides with slightly concaved linear micro-topography at Site N. Significant thermokarst subsidence and seasonal thaw settlement were measured along a Yedoma hill slope both by ground survey and DInSAR at Site M. The intensive permafrost degradation on the slopes was also confirmed by frozen ground coring and optical image analysis. The ground measurements of surface displacement were aligned well with DInSAR displacement using UAVSAR and ALOS2 data except for the anomaly subsidence along the troughs of ice-~wedge polygons at earlier thermokarst stages. Less intensive ground surface displacement was observed at Site S, underlain by less ice-rich permafrost. Our results indicate that seasonal thaw settlement was governed mainly by spatial variation in soil frost-susceptibility and thermokarst subsidence by ground ice distribution.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/997364

2022057086 Jacquemart, Mylene (ETH Zurich, Zurich, Switzerland); Shugar, Daniel H.; Higman, Bretwood M.; Loso, Michael; Kääb, Andreas; Leinss, Silvan and Geertsema, Marten. Detecting the imprint of climate change in high mountain hazards; challenges and opportunities [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP51B-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

On 7 February 2021, a massive debris flow, triggered by a 27´106 m3 rock and ice avalanche released from Ronti Peak at an elevation of around 5300 m asl, descended the Ronti Gad, Rishiganga, and Dhauliganga valleys. The event claimed the lives of more than 200 construction workers working at two hydro-power projects, the infrastructure of which was completely destroyed. The sediment plume could be tracked all the way to the Indian Ocean. On two summer days, 5 August 2013 and 25 July 2015, the detachments of Flat Creek Glacier in Wrangell St. Elias National Park, Alaska, removed most (24.4-31.3´106 m3) of the little glacier's ice in just a few moments. Downstream of the glacier, ice and debris buried 400-year old forest as far as 11 kilometers from the source and up to 30 m thick. Flat Creek glacier is one in a series of glaciers that have experienced this catastrophic fate that we are only just beginning to understand. Not far from Flat Creek, in Prince William Sound, Alaska, a large landslide is threatening to fall into the fjord below, as the glacier that previously buttressed its toe is retreating. What became known as the Barry Arm landslide is now threatening to collapse into a deep, ice-free waters where it can generate a far reaching tsunami. But the Barry Arm landslide is not a unique case. Rather, geomorphic evidence all around coastal Alaska indicates we may need to rapidly alter the way we think about coastal landslide hazards. These events, and many alongside them, are in line with what has been predicted for decades: Anthropogenic climate change will lead to an increase of hazardous mass movements from alpine regions due to glacier retreat and permafrost thaw. And reports from all around the world seem to support this notion. However, with rapidly increasing coverage of events happening around the globe through social media and readily available satellite imagery, it is hard to disentangle the increase in observations from the true signal. Here, we put these recent events in context with climate change and highlight the need, challenges, and opportunities of detecting the imprint of climate change on high mountain hazards.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/806812

2022059985 James, Stephanie R. (U. S. Geological Survey, Denver, CO); Minsley, Burke J.; McFarland, Jack W. and Waldrop, Mark P. Tracking soil thaw and permafrost degradation across multiple timescales using ambient seismic noise [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract S32B-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

High-latitude ecosystems are experiencing substantial changes in permafrost stability-driven by both above and below ground factors-which can significantly impact plant, animal, and human communities as well as the global carbon budget. Detecting changing conditions below Earth's surface is critical to understanding the mechanisms and impacts of permafrost degradation. The recent rise in passive seismic methods brings new opportunities for quantifying subtle changes in water and ice content in permafrost environments, across a range of temporal and spatial scales. Here, we present results from a multidisciplinary field study at a thermokarst site in Interior Alaska where ambient seismic noise has been recording continuously on a small-aperture seismic array since April 2018. By using multi- and single-station coda-wave interferometry, we track relative velocity variations caused by freeze/thaw and water saturation changes within the near surface (<5 m depth) on daily, seasonal, and interannual timescales. Single-station cross-correlations captured velocity variations (dv/v) at each seismometer location, ranging seasonally between +2.5% and -15% relative to January 2019. Discrete drops in summer velocity correspond with rainfall events and increases in soil moisture and thaw depth, while winter variations signify subtle changes in near-surface ice content in response to air temperature fluctuations. Multi-station dv/v records were inverted using 2D tomography to produce timelapse images showing spatial patterns in water accumulation and thaw extent across the study site, highlighting potential areas of enhanced thaw and thermokarst expansion. Lastly, horizontal-to-vertical spectral ratios provided an alternative method for quantifying high-temporal resolution changes in active-layer thaw depth and soil moisture at individual sites. Yearly records of seasonal thaw progression indicate maximum thaw depth is deepening at some sites, primarily those suspected to have higher ground-ice indicating these areas are most vulnerable to future thaw. These results demonstrate the power of passive seismic techniques for detailed monitoring of near-surface thermal and hydrologic conditions within the rapidly changing permafrost domain.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/798202

2022055970 Jones, Benjamin M. (University of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, AK); Kanevskiy, Mikhail Z.; Shur, Yuri; Jorgenson, Mark T.; Iwahana, Go; Gaglioti, Benjamin; Jones, Melissa Ward; Larsen, Chris; Miller, Eric A.; Miller, Charles E. and Jandt, Randi. Degradation, stabilization, and initial aggradation of permafrost following an Arctic tundra fire [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1443, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Anaktuvuk River fire severely burned more than 1,000 km2 of arctic tundra in northern Alaska in 2007. Since the fire burned tundra vegetation and organic-rich soils underlain by a range of permafrost ground ice conditions, long-term observations of the landscape can help understand how the Arctic will change as more area burns. Some outstanding questions in this regard are: What is the trajectory and longevity of fire-induced permafrost degradation, and can permafrost in burned tundra landscapes stabilize following disturbance? Post-fire thaw-related effects at the Anaktuvuk River tundra fire through 2014 included the development and stabilization of localized active layer detachment slides and retrogressive thaw slumps, but the widespread and ongoing degradation of ice wedges. In this study, we update observations on near-surface permafrost in the Anaktuvuk River tundra fire burn area through 2021 using ground temperature measurements, cryostratigraphic studies, optical satellite imagery, and repeat airborne LiDAR data. We focus on a 50 km2 mosaic of ice-rich permafrost terrain in the Yedoma "silt belt" region of the burn. Annual mean ground temperature data collected at a depth of 1 m at burned and unburned observation sites show that the permafrost was 2.2°C warmer in the burned area 7-8 years following the fire, but only 1.1°C warmer 12-13 years post-fire. Several permafrost boreholes drilled in ice wedge troughs and polygon centers 14 years post-fire revealed the presence of a thaw unconformity that was overlain by a 10-25 cm thick ice-rich intermediate layer, indicating aggradation of permafrost following thermokarst development. Remote sensing-based change detection of surface water in thermokarst pits and repeat analysis of airborne LiDAR data collected in 2009, 2014, and 2021 add further supporting evidence for the cessation of thaw subsidence of the ice-rich permafrost terrain. Taken together, our observations highlight that the initial degradation of ice-rich permafrost terrain in the first ten years following the Anaktuvuk River tundra fire was followed by a period of permafrost aggradation and terrain stabilization. The result is a post-fire landscape that shows evidence of being disturbed by fire-induced thaw, but one that is likely more resilient to future disturbance.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/847668

2022059929 Jones, Melissa Ward (University of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, AK); Jones, Benjamin M.; Gannon, Glenna; Schwoerer, Tobias; Kanevskiy, Mikhail Z.; Shur, Yuri; Gaglioti, Benjamin; Parlato, Nicholas; Fedorov, Alexander; Ping, Chien-Lu; Chapin, Carolyn; Sutton, Iris; Russell, Jill M.; Russell, Dave E.; St. Pierre, Brad and St. Pierre, Christine. Understanding permafrost and agriculture interactions for ensuring sustainable, adaptable and resilient permafrost-agroecosystems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55J-0526, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The rapid degradation of near-surface permafrost is widespread, being driven by a warming Arctic as well as changes in land-surface disturbances with cascading effects on high-latitude ecosystems and communities. Most research is currently focused on the biophysical changes of the Arctic System and understanding how these biophysical changes are affecting northern economies and industry sectors is still in its infancy. A new agricultural frontier is expected to emerge in the discontinuous permafrost region, where suitable area to grow globally important crops (for example, wheat, potato, and maize) is predicted to disproportionately increase. While agricultural activity has long been practiced in areas of discontinuous permafrost, the interactions between cultivation and permafrost has received little attention to date and the potential impact to the future of critical crop production from climate-driven thaw following land clearing is not yet understood. This research primarily focuses on land clearing and cultivation of permafrost terrain in the lower Tanana River Valley, Alaska, USA, where conventional agricultural practices began in the early 1900s and continue to expand through present day. Using remote sensing techniques, we present historical image time series of the expansion and evolution of cultivation practices and their interaction with near-surface permafrost between 1938 and 2021. We also quantify thaw subsidence in cultivated fields between 2011 and 2021 using LiDAR and UAV survey data. Based on remote sensing and prior field observations, we have developed four conceptual scenarios of permafrost degradation associated with cultivated fields that reflect the type of permafrost present and the agricultural practices being used. Furthermore, we discuss how co-producing knowledge between researchers and the Arctic farming community can support adaptable, resilient, and sustainable permafrost-agroecosystems. A better understanding of the feedbacks and interactions between cultivation and permafrost, co-produced with and for Arctic farmers, is necessary to ensure the northern expansion of agriculture is solution-oriented and successful.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/813745

2022055972 Jones, Melissa Ward (University of Alaska Fairbanks, Fairbanks, AK); Jones, Benjamin M.; Walker, Donald A.; Kanevskiy, Mikhail Z.; Shur, Yuri; Peirce, Jana; Zwieback, Simon; Breen, Amy Lynn; Liljedahl, Anna; Natali, Susan; Miller, Charles E.; Larsen, Chris and Iwahana, Go. Preliminary assessment of the micro-topographic impacts of ice-wedge systems using remote sensing and field observations [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1447, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Ice-wedges, forming polygonal terrain, are the most common type of massive ground ice in the Arctic. In northern Alaska, approximately 60% of the Arctic Coastal Plain is estimated to be underlain by wedge ice. In this region, ice-wedge surfaces are typically located near the permafrost table, so any increases in active layer thickness will melt the top surface of the ice-wedge, causing thermokarst. This impact on micro-topography further impacts surface hydrology, snow cover distribution, geochemical fluxes, vegetation patterns, and ground temperatures in ice-wedge systems. Our research is using sub-meter LiDAR and UAV datasets to quantify the micro-topography of ice-wedge systems within the ABoVE domain regions of Alaska and the Yukon and Northwest Territories of Canada. We present preliminary results from sites in Alaska using field data collected at Prudhoe Bay between 2014 and 2016 and from the Teshekpuk Lake Observatory (TLO) between 2020 and 2021. Generally, ice-wedge polygon centers have the lowest mean annual ground temperatures (MAGT; depths ranging between ground surface and 1 m), the warmest summer, and the coolest winter ground temperatures when compared to ice-wedge troughs. At Prudhoe Bay, topography varied by »0.5 m and MAGT varied by »2.2 °C between polygon centers and troughs. At the TLO, topography varied by »0.4 m and MAGT by »0.4 °C. Ground temperature trends between ice-wedge troughs of varying depths were less clear and more analysis is needed to partition ground temperature trends based on soil moisture and surface vegetation cover. Recent observations show ice-wedges are degrading rapidly throughout the Arctic. Micro-topography evolution will drive significant ecosystem changes and feedbacks. It is critical to better understand these fine-scale system processes to ensure we understand the large-scale impacts of these ubiquitous features in permafrost affected areas. Future research will focus on the variability in ice-wedge system micro-topography as a driver of key arctic ecosystem characteristics and processes, including ground temperature, thaw depth, soil moisture, snow depth, vegetation height and type, CO2, and CH4 fluxes.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/918008

2022059931 Kholodov, Alexander L. (University of Alaska Fairbanks, Fairbanks, AK). Potential for development of the process of thermokarst in the zone of discontinuous permafrost in Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55J-0530, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

As a climatically driven phenomena permafrost recently is undergoing the process of degradation following the global trends of air warming. This process can be subdivided in two stages - (1) warming of frozen deposits to the range of phase transition of soil water (sensible heat) and (2) intensive melting of ground ice (latent heat). In Alaska within the zone of discontinuous permafrost now days mean annual ground temperature had reached the critical values and the process of degradation passes in the second phase. Depending on ground ice content it might be realized by two ways: first - formation of taliks, i.e. perennial unfrozen horizon between seasonally frozen layer and permafrost, when ice content does not exceed soil porosity and second - the thermokarst, i.e. subsidence and collapsing of the ground surface due to melting of excessive ground ice. Within the boreal forest ecotype which spans the most of the area of Interior Alaska presence of ice-rich deposits depends on the history of wild fires, while within the tundra biome which occurs in this region at the hilltops (alpine tundra) and at the Seward Peninsula excessive ground ice is more common feature. In this presentation we will discuss the case studies of the potential of thermokarst development in the alpine tundra north from Alaska range (Healy) and tundra at Seward Peninsula (Council). Deep (5 to 7 meters) frozen cores were collected and analyzed for cryostratigraphy and the basic soil properties. The values of volumetric ice content exceed the soil porosity in both analyzed cores. Three boreholes (2 at Healy and one at Council) were instrumented for long-term geothermal measurement. Results of temperature measurements indicate extreme deepening of active layer and active thawing of upper horizons of permafrost. Visible evidences of the thermokars development were also noticed at both research sites.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/969427

2022057036 Kim, Kyung Yoon (University of Virginia, Department of Engineering Systems and Environment, Charlottesville, VA); Kansara, Prakrut Haresh; Haagenson, Ryan; Rajaram, Harihar and Lakshmi, Venkataraman. A comparison of first-order permafrost estimates in high mountain Asia using remotely sensed land surface temperature, air temperature, and snow reanalysis products [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0936, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The projected thawing of alpine permafrost in the 21st century will trigger major challenges related to slope instability, carbon emissions, public health, and water resource management in mountain communities and their downstream neighbors. Thus, accurate estimates of permafrost extent at high resolution are desirable, especially in data sparse regions like HMA, where highly rugged terrain renders in-situ data collection difficult. By definition, a mean annual ground temperature (MAGT) of or below 0°C for at least two consecutive years determines permafrost presence in a given area. However, the mean annual air temperature (MAAT) and increasingly, the mean annual land surface temperature (MALST) are often used as proxy variables in lieu of direct MAGT measurements due to the accessibility of weather station and remotely sensed observations. This research leverages the sampling frequency and spatial coverage of gap-filled daily MODIS (Moderate Resolution Imaging Spectroradiometer) LST and monthly AIRS (Atmospheric Infrared Sounder) AT products to map permafrost zonation indices (PZI) based on a cumulative normal distribution function used by Gruber (2012) in HMA. Additionally, mean snow depths for the HMA region provided by Liu et al. (2021) are incorporated into a modified equation based on weighted freezing/thawing degree day indices originally derived by Smith & Riseborough (2002) to account for the insulating effect of snow cover on the MAGT. Preliminary estimates of total permafrost area are calculated based on the resulting PZI for the following sub-regions of HMA: the Tien Shan (94,300 km2), Pamirs (159,000 km2), Hindu Kush (36,800 km2), Himalayas (151,000 km2), Qinghai-Tibetan Plateau (1,380,000 km2), and Hengduan (105,000 km2).

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/808862

2022059921 Kobylkin, Dmitry (Russian Academy of Sciences, Siberian Branch, V.B. Sochava Institute of Geography, Irkutsk, Russian Federation); Sizov, Oleg; Kuklina, Vera; Bilichenko, Irina; Krasnoshtanova, Natalia; Petrov, Andrey N.; Bogdanov, Victor and Shiklomanov, Nikolay I. Connecting permafrost degradation and informal road network development in subarctic taiga [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC52C-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The climatic changes are having a significant impact on highly sensitive landscapes of the Eurasian boreal region. Simultaneously, Siberian Taiga is subjected to increasing anthropogenic pressure associated with resource extraction, transportation, and recreational infrastructure development. The combination of climate- and human-induced changes has significant impacts on warm sporadic and/or discontinuous permafrost of the region. In turn, permafrost changes have direct implications for land use, the economy, subsistence, and the social life of local residents. This paper focuses on landscape indication of permafrost degradation associated with the network of informal (e.g., lacking official state control and governance) roads in boreal landscapes of the Northern Baikal region of Russia. Such roads were initially developed for various natural resource exploration and extraction activities and are presently used by the local Indigenous population to access substance grounds. Based on the combination of remote-sensing imagery, detailed field studies at representative sites, and traditional knowledge of local residents we have analyzed the relations between permafrost degradation and surface disturbance associated with informal roads and spatially assessed the vulnerability of permafrost-affected landscapes to the development and use of informal roads. The results of our analysis will be utilized for a comprehensive assessment of the sustainability of Eurasian boreal landscapes for subsistence activities under climatic and development pressures.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/875085

2022057061 Koenig, Cassandra (BGC Engineering, Vancouver, BC, Canada); Arenson, Lukas U.; Hauck, Christian and Hilbich, Christin. Modelling water release from degrading permafrost in arid mountain environments [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55D-0626, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Numerical cryo-hydrogeology models can be useful tools for understanding thermal and hydrological feedbacks that influence water flow in periglacial environments. With climate change expected to modify permafrost distribution globally, there is growing interest in developing such models for planning purposes, particularly in arid mountainous environments where headwaters can be important water sources to downstream users. In the arid Central Andes, permafrost is ubiquitous and debated as a possible resource to moderate water scarcity under climate change and drought. At many locations in the region, permafrost is in disequilibrium with existing climate and therefore expected to degrade even if current air temperatures are maintained. The coupled finite element codes TEMP/W and SEEP/W were used to explore a range in hydrologic outcomes from degrading permafrost within a typical watershed for such an arid region, subject to a suite of characteristic permafrost distribution, ground ice content and hydrogeologic conditions. A 3 km-long 2D cross-sectional numerical model was developed using simplified topography (altitude up to ~6000 m), and ground temperatures representative of the region. The model uses constitutive relationships that consider conductive and advective heat transport, as well as unsaturated water flow, and includes surface boundary conditions derived from local monitoring data. Predictive simulations were performed to estimate changes in water quantities and flow-paths should current temperature conditions in the watershed persist. Preliminary results for a continuous permafrost case suggest an overall decrease in downstream discharge as ground-ice thawed. As permafrost degraded laterally and the active layer thickened, supra-permafrost water migrated downward through the unsaturated zone toward the regional ground water system. It is noted that these results are strongly subject to the assigned initial conditions and simplified topography. Future efforts will explore scenarios with more complex landform topography and permafrost distribution, under climate change influences.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/998416

2022059961 Kuras, Oliver (British Geological Survey, Nottingham, United Kingdom); Cimpoiasu, Mihai; Harrison, Harry; Meldrum, Philip; Wilkinson, Paul B. and Chambers, Jonathan Edward. Year-round geoelectrical monitoring of recently deglaciated soils in the High Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS11A-02, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Accelerated warming in the Arctic is causing significant reductions in the extent of glaciers and ice sheets, which thus far have dominated the Arctic landscape. As glaciers retreat, pioneer soils are uncovered, supporting emerging microbial communities which drive biogeochemical transformations. Understanding these emerging systems and their impact on the global carbon budget is important, which makes monitoring processes at the soil-atmosphere-cryosphere boundary essential. Geoelectrical methods have emerged as a fast, cost-effective and minimally invasive way of imaging soil moisture dynamics in the shallow subsurface. The SUN-SPEARS project aims to investigate the benefits of 4D geoelectrical monitoring on an emerging forefield at the Midtre Lovenbreen glacier near Ny-Alesund, Svalbard. Year-round under-snow geoelectrical tomography requires careful consideration of power requirements and system resilience. BGS PRIME technology has been adapted to facilitate low-power remote measurements, allowing over-winter operation without mains recharge. Undisturbed cores were sampled from the top soil horizon at four different locations on a forefield chronosequence, with the youngest soils found closest to the glacier snout. Soil ages correspond to roughly 5, 20, 80 and 120 years. Additionally, in July 2021, two PRIME systems were deployed at sites corresponding to very young and medium ages. The systems use arrays of surface electrodes to measure electrical resistivity within the uppermost ~2 m of soil, allowing assessment of moisture dynamics and freeze-thaw within the permafrost and the active layer. These processes are currently underexplored due to the inaccessibility of field sites outside of the short Arctic summer. Solar and wind power help supplement battery power whenever possible. We present early results obtained during PRIME installation and compare these with laboratory measurements on soil cores. Pedophysical relationships describe changes in resistivity with temperature and moisture content. These will serve to calibrate the year-round datasets. Furthermore, integrated analysis of the geoelectrical datasets with other environmental parameters and microbiological activity will contribute to a more comprehensive biogeochemical model of soil evolution over time.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/936849

2022056021 Kwon, Min Jung (University of Hamburg, Hamburg, Germany); Ballantyne, Ashley; Ciais, Philippe; Qiu, Chunjing; Salmon, Elodie; Guenet, Bertrand; Goeckede, Mathias; Euskirchen, Eugenie Susanne; Nykanen, Hannu; Schuur, Edward; Turetsky, Merritt R.; Dieleman, Catherine M. and Zona, Donatella. Drying reduces carbon sink strength and carbon stock in northern circumarctic peatlands [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45K-1757, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Peatlands in the high latitudes have accumulated over 400 Pg of carbon (C) because saturated soil conditions inhibit carbon decomposition. This substantial amount of C in Arctic and Boreal peatlands is potentially subject to increased decomposition when they are dried due to anthropogenic activities or permafrost thaw. Here, we use a version of the Organizing Carbon and Hydrology In Dynamic Ecosystems model modified to northern peatlands (ORCHIDEE-PEAT-METHANE) and investigate the changes of C fluxes as well as C stock in response to peatland drying. By calibrating key parameters associated with CO2 and CH4 fluxes, we simulate CO2 and CH4 fluxes of Arctic and Boreal 6 peatland sites, within which drying manipulation experiments were carried out. Without drying, Arctic and Boreal peatlands currently act as C sinks in most years. Drying by 20 cm compared to the in-situ control water table (WT) decreased the net annual CO2 sink strength by up to 80% and CH4 emission by up to 75%, and the decreasing rate differed by initial WT and the existence of permafrost. Due to larger increases in CO2 emissions than the reductions in CH4 emissions, peatlands C stock decreased in response to 100 years of drying. Predicting the peatland C stock is highly uncertain because of potential secondary effects, such as changes in C input (e.g., increasing plant biomass and litter input) and C loss (e.g., deeper rooting depth accelerating C decomposition in deep soils), but peatland drying likely accelerates C loss, more strongly in non-permafrost peatlands.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/935741

2022057014 Lainis, Alexi (Denver Water, Denver, CO); Neupauer, Roseanna; Koch, Joshua and Gooseff, Michael N. Numerical simulation of groundwater flow in partially frozen soils to investigate aufeis formation [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C22C-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Aufeis (also known as icings) are large sheet-like masses of layered ice that form in river channels in arctic environments, where permafrost is present at shallow depths and an upper active layer is frozen part of the year. Aufeis are important sources of water for arctic river ecosystems because they melt late into the summer, providing a source of water to rivers when other water resources are reduced. The aim of this research is to use numerical simulations to evaluate a conceptual model of subsurface hydrogeothermal conditions that can lead to the formation of aufeis in the Kuparuk aufeis field on the North Slope of Alaska. Above the permafrost, ~15 m of the shallow subsurface remains unfrozen all year long (also known as a talik). Groundwater in this talik is forced to the surface through unfrozen gaps in the active layer when it encounters a fully frozen subsurface downstream. We developed a 2-D heterogeneous vertical profile model to show that subsurface water can flow to the land surface through subvertical high permeability pathways during winter months when the lower permeability soils near the land surface are frozen. The water that exits the subsurface would then freeze on the surface, contributing to aufeis formation throughout the winter. We have performed sensitivity analyses on subsurface properties and surface temperature forgings. We show that certain parameter sets produce a contiguous unfrozen pathway through which groundwater can flow, reducing the quantity of water that is available to exit at the surface and form aufeis; while other parameter sets lead to conditions consistent with the conceptual model. An understanding of the processes that lead to the formation of aufeis is necessary to be able to predict how rising temperature may affect aufeis formation and the availability of water in Arctic river ecosystems.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/833296

2022059944 Lamb, Jack (Lawrence Berkeley National Laboratory, Berkeley, CA); Wielandt, Stijn; McClure, Patrick; Uhlemann, Sebastian; Wang, Chen; Peruzzo, Luca and Dafflon, Baptiste. Development and assessment of a quick subsurface thermal characterization method to map soil thermal and physical properties [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H35C-1053, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The subsurface composition including carbon, minerals, and water are essential attributes of terrestrial ecosystems which are potentially subject to change under a warming climate. Mapping their distribution and heterogeneity is critical to understanding physical and biological processes modulating these changes, yet this task remains a significant challenge using traditional measurement techniques. Recent development of low-cost Distributed Temperature Profiling (DTP) systems provides improved spatial resolution for measuring in-situ temperature time series. Such spatial refinement holds promise for characterizing the heterogeneity of soil thermal and physical properties, leading to a better understanding of subsurface stores. In order to minimize the amount of time needed to estimate thermal parameters from temperature time-series, here we developed a novel combination of instrumentation and software tools to quickly measure soil thermal properties with high spatial resolution. The system was used at about 300 locations in the upper East River watershed in Colorado, USA and in a discontinuous permafrost environment near Nome, Alaska. For this study, DTP probes were specially designed to be quickly deployed and recovered. Each location required between 1 and 5 minutes of active work, enabling up to a few hundred measurement locations per day. For each location, temperature time series were recorded for at least 30 minutes along a 75 cm vertical profile with 5 cm spacing. Along with recording temperature, the first 5 minutes of temperature equilibration data were compared with results from a forward finite volume model, allowing for inversion of thermal parameters. Our approach was assessed with independent measurements of the soil thermal parameters. Combined with measured petrophysical relationships, these inversion results provided insight into the distribution of and heterogeneity of soil composition and moisture content. The results underline the potential of this novel approach, as well as the remaining challenges, such as unknown contact resistance and variable petrophysical relationships.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/835855

2022057053 Lara, Mark J. (University of Illinois at Urbana Champaign, Urbana, IL); Chen, Yaping and Jones, Benjamin M. Recent warming reverses forty-year decline in catastrophic lake drainage and hastens gradual lake drainage across northern Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-03, illus. incl. sketch map, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Lakes represent as much as ~25% of the total land surface area in lowland permafrost regions. Though decreasing lake area has become a widespread phenomenon in permafrost regions, our ability to forecast future patterns of lake drainage spanning gradients of space and time remain limited. Here, we modeled the drivers of gradual (steady declining lake area) and catastrophic (temporally abrupt decrease in lake area) lake drainage using 45 years of Landsat observations (i.e., 1975-2019) across nearly 35,000 lakes spanning climate and environmental gradients across northern Alaska. We mapped lake area using supervised support vector machine classifiers and object based image analyses using five-year Landsat image composites spanning ~385,000 km2. Drivers of lake drainage were determined with boosted regression tree models, using both static (e.g., lake morphology) and dynamic predictor variables (e.g., temperature). Over the past 45 years, gradual drainage decreased lake area between 10-16%, but rates varied over time as the 1990s recorded the highest rates of gradual lake area losses associated with warm periods. Interestingly, the number of catastrophically drained lakes progressively decreased at a rate of »37% decade-1 from 1975-1979 (102 to 273 lakes draining year-1) to 2010-2014 (3 to 8 lakes draining year-1). However this 40 year negative trend was reversed during the most recent time-period, with observations of catastrophic drainage among the highest on record, the majority of which occurred in northwestern Alaska. Gradual drainage processes were driven by lake morphology, summer air and lake temperature, snow cover, active layer depth, and the thermokarst lake settlement index (CV=0.35), whereas, catastrophic drainage was driven by the length of growing season, total precipitation, permafrost thickness, and lake temperature (CV=0.67). Models forecast a continued decline in lake area across northern Alaska by 15 to 21% by 2050. However these estimates are conservative, as the anticipated amplitude of future climate change were well-beyond historical variability and thus insufficient to forecast abrupt "catastrophic" drainage processes. Results highlight the urgency to understand the potential ecological responses and feedbacks linked with ongoing Arctic landscape reorganization.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/794394

2022059979 Lattaud, Julie (ETH Swiss Federal Institute of Technology, Zurich, Switzerland); Eglinton, Timothy I.; Haghipour, Negar; Giosan, Liviu and Bröder, Lisa. Radiocarbon constraints on the sources and cycling of organic carbon in Mackenzie Delta lakes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract PP25D-0956, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic is undergoing accelerated changes in response to ongoing alterations to the climate system (Arctic report card 2019), and there is a need for local to regional scale records of past climate variability in order to put these changes into historical context. The Mackenzie Delta region (Northwestern Territories, Canada) is populated by numerous small shallow lakes. They are classified as no-, low- and high-closure lakes, reflecting varying degrees of connection to the river main stem, and as a result, have different sedimentation characteristics. As for much of the Arctic region, the Mackenzie Delta is expected to undergo marked environmental perturbations such as earlier melting of river ice. As a consequence, the annual flood pulse (freshet) may decline, potentially resulting in the disconnection of some lakes from the river, leading to their subsequent desiccation (Lesack et al., 2014; Lesack & Marsh, 2010). In contrast, abrupt permafrost thaw and enhanced thermokarst-related processes might lead to additional lake formation and deepening of already formed lakes. In this study, we used sediment cores originating from several lakes within the Mackenzie Delta, representing the three types of connectivity to the river (Lattaud et al., 2021). Radiocarbon and stable carbon isotopic signatures of two groups of compounds--fatty acids and isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs)--are employed as tracers of carbon supply to, and cycling within the different lakes. Short-chain fatty acids as well as GDGTs serve as putative tracers of microbial production while long-chain fatty acids originate from higher terrestrial plants. The carbon isotopic signatures are used to distinguish between the relative importance of carbon inputs derived from in situ production, as well as from proximal (lake periphery) and distal (Mackenzie River) sources to the different lakes in the context of their degree of connectivity. Down-core molecular 14C measurements provide insights into the temporal evolution of the lakes, providing context for their response to past and future climate change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/942827

2022059918 Lee, Walker (Cornell University, Ithaca, NY); MacMartin, Douglas; Visioni, Daniele and Kravitz, Ben. A geoengineered Arctic; optimizing high-latitude stratospheric aerosol geoengineering via seasonal injection and analyzing the effects on sea ice, permafrost, and ice sheet melt [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC35E-0735, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Stratospheric aerosol injection has been shown to increase summer sea ice extent, increase permafrost area, and reduce land ice sheet melt in earth system model simulations. High-latitude injection could preserve the Arctic climate more efficiently and safely than low-latitude injection; our simulated experiments take steps toward optimizing a high-latitude geoengineering strategy and analyzing the effects on the Arctic and global climates. Firstly, we demonstrate that seasonal injection is more efficient than year-round injection at high latitudes; because the Arctic receives much more sunlight in summer than in winter, concentrating the injection in the spring (so that aerosols are present through the summer) achieves greater aerosol optical depth and restores September sea ice twice as efficiently as year-round injection. Secondly, we design simulations that use springtime high-latitude injections to restore and maintain September sea ice, and we then examine the effects of these strategies on various Arctic and global climate metrics, including permafrost and ice sheet melt. Finally, we compare the impacts of our high-latitude experiments to the impacts of various low-latitude geoengineering strategies from previous studies.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/820230

2022057087 Li, Dongfeng (National University of Singapore, Department of Geography, Singapore, Singapore); Lu, Xixi; Walling, Desmond E.; Wasson, Robert James; Harrison, Stephan; Nepal, Santosh; Steiner, Jakob F.; Nie Yong; Immerzeel, Walter W.; Shugar, Daniel H.; Zhang, Ting; Yegorov, Alexandr and Bolch, Tobias. Climate change and landscape instability in High Mountain Asia [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP51B-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Climate change in High Mountain Asia (HMA) not only affects hydrological processes and Asian Water Tower but also results in landscapes instability and catastrophic geohazards, potentially threatening over 2 billion people's lives in the downstream river basins. Specifically, climate change is causing landscape instability through glacier retreat and detachments, permafrost thaw and associated landslides, debris flows, outburst floods from (pro)glacial- and landslide-dammed lakes with potential runout distances of hundreds of kilometers. Moreover, greater amounts of sediment are mobilised and fluvial sediment fluxes are increasing. Such instability threatens many existing and planned hydropower dams and reservoirs through dam failures, high sedimentation rates and associated storage loss, and high turbine abrasion reducing hydropower generation. Adaptation measures are urgently needed to inform sustainable and resilient development in the region. We recommend adaptation measures based on extensive and continual monitoring of the glaciers, permafrost, and unstable paraglacial landscapes, to better understand compound and cascading hazards. We also highlight future research directions regarding climate change and landscape instability in high mountain areas.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/847342

2022057062 Liljedahl, Anna K. (Woodwell Climate Research Center, Falmouth, MA); Jones, Matthew B.; Budden, Amber E.; Witharana, Chandi; Cervenec, Jason M.; Jones, Benjamin M.; Jones, Christopher S.; Marini, Luigi; Walker, Lauren; Hasan, Amit; Nitze, Ingmar; Wind, Galina; Brubaker, Michael; Thiessen-Bock, Robyn and McHenry, Kenton. The permafrost discovery gateway [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost thaw has been observed at several locations across the pan-Arctic in recent decades, yet the pan-Arctic extent and potential spatial-temporal variations in thaw are poorly constrained. Thawing of ice-rich permafrost can be inferred and quantified with satellite imagery due to the subsequent differential ground subsidence and erosion that in turn affects land surface cover. Information contained within existing and rapidly growing collections of high-resolution satellite imagery (Big Imagery) is here extracted across the Arctic region through a collaboration between software engineers, computer- and earth scientists. More specifically, we are a) developing geospatial data down to sub-meter resolution, and also b) enabling discovery and knowledge-generation through visualization tools. This cyberinfrastructure platform, the Permafrost Discovery Gateway (PDG), is being designed with input from users of the PDG, e.g. primarily the Arctic earth science community but also the general public. The PDG builds upon other NSF supported data management resources (Arctic Data Center and Clowder) and the Fluid Earth Viewer. The Fluid Earth Viewer, the first visualization tool implemented into the PDG, was initially created for the public to explore atmospheric and oceanographic visualizations in coarse spatial resolution (15 km) and is here modified to support permafrost geospatial products, and a number of community built analytic tools to identify permafrost artifacts within satellite imagery. New tools include the ImageryViewer and the PLotViewer, which are aimed for visualization and analysis of big data. The effort also includes workflow optimization of remote sensing code for pan-Arctic sub-meter scale mapping of ice-wedge polygons from optical imagery. We are additionally actively engaging with the user-community to ensure that the PDG becomes useful, both in terms of the type of data contained within the PDG and the design of the visualization tools. The PDG has the potential to fill key Arctic science gaps, such as bridging plot to pan-Arctic scale findings, while also serving as a resource informing decisions regarding the economy, security, and resilience of the Arctic region

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/996585

2022057074 Lilly, Michael R. (Geo-Watersheds Scientific, Fairbanks, AK); Brown, Jerry; Thornley, John; Tahirkheli, Sharon; Eitler, Mary Ann; Levine, Kristina; Kubacki, Elizabeth and Fu, Leyton. The Permafrost Monthly Alert (PMA) program; improving international access to permafrost literature in engineering and science [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract ED52A-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The U.S. Permafrost Association (USPA) and the American Geosciences Institute (AGI) developed the Permafrost Monthly Alert (PMA) program to enhance access and discovery of relevant and professionally reviewed international permafrost engineering and science literature on a regular monthly schedule. Results are made available in multiple locations on the Internet that are regularly indexed by major search engines. The monthly-updates portion of the PMA program are available through the USPA website (www.uspermafrost.org). The current ten-year collection (2012-2021(June)) includes over 113 monthly and special updates containing over 8,581 citations. The vast majority of the references have abstracts and are organized in five major categories: journals, conferences, thesis, reports and maps. Monthly accessions are uploaded to the AGI publicly accessible database COLD (developed from the Bibliography of Cold Regions Science and Technology database). COLD is a searchable database with more than 33,500 current and historical permafrost references, and indexed by various search engines. Average annual usage of the PMA service exceeded 11,700 inquiries (views by readers) for 2018 through 2020. The total usage from 2012 through July 2021 is over 89,000 inquiries. Special Alerts of permafrost-related conferences are a recent addition to PMA; over 200 abstracts were identified from the 2020 AGU Fall Meeting. The PMA Program utilizes the AGI reference database GeoRef. GeoRef is updated continuously from reference sources from over 106 countries and 44 languages. Reference sources include journals, reference libraries, conferences and other sources from over 8,000 national and international sources. From this ongoing retrieval of information, select terms are used to search GeoRef each month to develop the Monthly Alerts and to add to monthly updates of COLD. The content provided through this program also benefits other reference databases, such as the Canadian CanGeoRef Database. These results help demonstrate the benefits and importance of organizing references in strategic ways to improve both the timeliness and ease of access.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/998668

2022056008 Liu, Futing (American Geophysical Union); Kou Dan; Chen Yongliang; Xue Kai; Ernakovich, Jessica Gilman; Chen Leiyi; Yang Guibiao and Yang Yuanhe. Altered microbial structure and function after thermokarst formation [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-09, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost thaw could induce substantial carbon (C) emissions to the atmosphere, and thus trigger a positive feedback to climate warming. As the engine of biogeochemical cycling, soil microorganisms exert a critical role in mediating the direction and strength of permafrost C-climate feedback. However, our understanding about the impacts of thermokarst (abrupt permafrost thaw) on microbial structure and function remains limited. Here we employed metagenomic sequencing to analyze changes in topsoil (0-15 cm) microbial communities and functional genes along a permafrost thaw sequence (1, 10, and 16 years since permafrost collapse) on the Tibetan Plateau. By combining laboratory incubation and a two-pool model, we then explored changes in labile and stable soil C decomposition along the thaw sequence. Our results showed that topsoil microbial a-diversity decreased, while the community structure and functional gene abundance did not exhibit any significant change at the early stage of collapse (1 year since collapse) relative to non-collapsed control. However, as the time since the collapse increased, both the topsoil microbial community structure and functional genes differed from the control. Abundances of functional genes involved in labile C degradation decreased while those for stable C degradation increased at the late stage of collapse (16 years since collapse), largely driven by changes in substrate properties along the thaw sequence. Accordingly, faster stable C decomposition occurred at the late stage of collapse compared to the control, which was associated with the increase in relative abundance of functional genes for stable C degradation. These results suggest that upland thermokarst alters microbial structure and function, particularly enhances stable C decomposition by modulating microbial functional genes, which could reinforce a warmer climate over the decadal timescale.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/809197

2022055964 Lockwood, Margaret (University of Kansas, Lawrence, KS); Seitz, Taylor J.; Haan, Tracie and Drown, Devin. Changing soil communities in the Arctic; impact of disturbance induced permafrost thaw on microbial communities [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15B-1423, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Disturbance events such as wildfires, drought, deglaciation, and infrastructure development are frequent. Climate change impacts the frequency and intensity of disturbances. Disturbance events create changes in the ecosystem including permafrost thaw, which may lead to changes in plant and microbial community composition. The specific changes in microbial community composition changes in response to permafrost thaw remain unclear. Comparing disturbed and undisturbed soil communities could indicate changes in greenhouse gas flux triggered by permafrost thaw. This comparison could also lead to the identification of pathogens released from permafrost, which impact human and environmental health. How does disturbance induced permafrost thaw impact microbial communities? We explore this question using active layer soil samples from a permafrost thaw disturbance gradient located in Interior Alaska. This permafrost thaw gradient was created in 1947 aiming to mimic wildfire disturbance and study the impact of disturbance on permafrost. One plot was left undisturbed and is underlain with permafrost. In the second plot, the top level of vegetation was removed inducing permafrost thaw of five meters. In the third plot, vegetation and organic matter was removed inducing a substantial thaw of ten meters. We collected soil samples across this gradient in both 2018 and 2021 to document changes over time. Through characterizing the soil microbial communities using the 16S rRNA gene region, we find a variation in predominant taxonomic classes including Polyagnia, Vicinamibacteria, and Verrucomicrobiae. Disturbance increased diversity and decreased soil acidity. We also observed changes in soil chemistry that may provide clues to changes in microbial communities. Moreover, Acidobacteriae, a microbe class known to indicate healthy plant growth, is largely absent from the site with substantial permafrost thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/959045

2022055980 Loranty, Michael M. (Colgate University, Department of Geography, Hamilton, NY); Talucci, Anna; Berner, Logan T.; Breen, Amy Lynn; Buma, Brian; Delcourt, Clément; Dieleman, Catherine M.; Douglas, Thomas A.; Frost, Gerald V., Jr.; Gaglioti, Benjamin; Gibson, Carolyn; Hewitt, Rebecca E.; Hollingsworth, Teresa; Lara, Mark J.; Mack, Michelle C.; Manies, Kristen; Natali, Susan; O'Donnell, Jonathan A.; Olefeldt, David; Paulson, Alison K.; Rocha, Adrian V.; Rogers, Brendan M.; Sistla, Seeta; Sizov, Oleg; Turetsky, Merritt R.; Veraverbeke, Sander and Walvoord, Michelle A. A synthesis of wildfire impacts on permafrost thaw depth across Arctic and boreal ecosystems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B23C-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Amplified climate warming across northern high latitudes has increased the annual area burned in Arctic and sub-Arctic ecosystems in recent decades. While fires have occurred across the region for millennia, this recent intensification of the fire regime has the potential to alter regional ecosystem structure and function in ways that will act as positive feedbacks to Earth's climate. In ecosystems underlain by permafrost, combustion of insulating soils and vegetation, surface charring, and direct effects of warming all contribute to increases in permafrost thaw, thermokarst development, and ground surface subsidence after fire. To achieve a broader understanding of how fire impacts permafrost, we assembled a dataset of active layer depths spanning the pan-Arctic and -Boreal regions. Our data set includes 50,000 active layer depth measurements that span a range of boreal and tundra ecosystems. The data set includes sites that represent over 70 unique fires in North America and Eurasia with measurements ranging from 0 to 60 years post-fire accompanied by reference measurements from nearby unburned areas. On average, we find greater increases in depth of thaw in boreal ecosystems (»20 cm or 35%) relative to tundra ecosystems (»6 cm or 15%) despite mean number of years post-fire being greater for boreal forests (»16 and »8 years post-fire for boreal and tundra, respectively). These patterns are maintained when data are restricted to only active layer depth (i.e mid growing season) or active layer thickness (i.e. end of season maximum depth) measurements. Using information on climatic and ecological factors, we analysed the factors that drive heterogeneity in wildfire impacts on active layer dynamics across spatial and temporal scales increasing our understanding of how concurrent changes in climate and fire regimes will impact active layer dynamics.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/818424

2022055966 Ludwig, Sarah (Lamont-Doherty Earth Observatory, Palisades, NY); Natali, Susan and Commane, Roisin. Hot spots of methane and carbon dioxide fluxes from eddy covariance measurements in the Yukon-Kuskokwim Delta, Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1432, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic stores vast quantities of carbon in soil and permafrost that is sequestered from the active carbon cycle. The Arctic is now warming at an accelerated rate and recent research has shown that increasing emissions of methane and carbon dioxide from ecosystems is causing the Arctic to switch from a net sink to a net source of carbon to the atmosphere in some locations. Atmospheric models of the circumpolar Arctic using airborne methane data have shown the Yukon-Kuskokwim (YK) Delta to be a regional hot spot of methane emissions, but there have been few on the ground measurements of methane flux to properly identify and attribute the specific ecosystems contributing to these high fluxes. The YK Delta is located in subarctic tundra with discontinuous carbon-rich permafrost. In this study we report results from carbon dioxide and methane fluxes from an eddy covariance tower installed in the YK Delta in July 2019. Fluxes for both carbon dioxide and methane were similar in seasonal amplitudes to tundra North Slope flux tower sites such as Toolik Lake and Imnaviut, though with a longer growing season. The YK Delta was a net sink of carbon dioxide through the summer, but became a net carbon dioxide source by September 2019 and October 2020. Methane fluxes were positive year-round but peaked in September 2019. We used footprint modeling and high-resolution landcover classifications derived using machine learning to decompose the landscape-level flux into the influence from respective landcover types. Though the peak footprint influence was usually over tundra, the highest methane fluxes came predominantly from wind directions corresponding a peatland fen and an area of disturbed permafrost near the edge of the flux footprint. This study demonstrates the importance of carbon dioxide and methane flux observations in understudied, heterogenous tundra.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/978259

2022057072 MacDonald, Erin (Woodwell Climate Research Center, Falmouth, MA); Virkkala, Anna-Maria; Gerlt, Bob; Rogers, Brendan M.; Fiske, Greg; Watts, Jennifer; Grayson, John; Treharne, Rachael; Potter, Stefano and Natali, Susan. UnstableGround; an interactive website to visualize and communicate how the Arctic is changing [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract ED34A-12, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic, comprising the tundra and boreal biomes, is warming more rapidly than anywhere else on the planet, prompting scientific endeavors to increase in recent years. As the body of scientific knowledge continues to grow, so too does the challenge of communicating these findings. This is of particular concern because changes in the Arctic will have implications for the Earth system and society on local, regional, and global scales. Despite the far-reaching implications, most people who live in lower latitudes are unaware of the state of the Arctic or how rapidly it is changing. To increase awareness of the rapidly changing Arctic, scientific information needs to be shared in different ways beyond academic publications, particularly through stories that resonate with broader audiences. To this end, we created a science communication and data visualization website using the Esri Hub platform. We combined compelling photographs of the Arctic with informative maps and statistics to showcase how climate change is affecting Arctic ecosystems, permafrost, fires, and carbon. We included interactive mapping applications that encourage users to engage with the data more effectively by, for example, comparing the rate of warming in their location to that in the Arctic region. The website is designed to engage different types of audiences, including the general public, students, policy-makers, and media. In addition to the clear language and emphasis on visuals that will resonate with the general public, we include maps with long-term monitoring of key variables for geospatial specialists and other scientists, and distill complex information into stories that are relevant to policy-makers. In the future, we plan to expand our community and data availability components to include two-way information sharing and comprehensive data sets, as well as different content types such as blogs, infographics, and news. Our site provides broad audiences with important information through various media that helps them to better understand the changing Arctic and its local to global impacts.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/969471

2022057011 Mack, Mikhail (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Quinton, William L.; McLaughlin, James and Hopkinson, Chris. Latitudinal permafrost peatland distribution and land cover changes in the Hudson Plains, Canada [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B55D-1231, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Thawing discontinuous permafrost in subarctic peatland-dominated landscapes is increasingly recognized as an indicator of a warming climate and potentially shifting peatland-dominated landscapes from atmospheric carbon store to source. Furthermore, in certain discontinuous permafrost landscapes (e.g., northwest Canada) the thaw of permafrost peatlands leads to a reorganization of near-surface flow paths as permafrost-free peatlands expand, connect, merge, and drain. Collectively, these permafrost-thaw-driven land cover and hydrologic changes have increased runoff and altered biogeochemical cycles threatening natural resources and critical infrastructure in Indigenous peoples' traditional territories along with aquatic and terrestrial wildlife habitat. Owing to the region's remote position and vast scale, comparatively less is known about the land cover and hydrological impacts of permafrost thaw in the Hudson Plains, the world's third largest peatland complex (370,000 km2) and southern most extent of non-alpine permafrost. Using a high-resolution LiDAR DEM, historical air photographs, and recent panchromatic and multispectral satellite imagery along a latitudinal transect, this study aims to answer two fundamental questions: (1) Which permafrost peatland forms occur along a latitudinal transect? and (2) where have permafrost peatland land cover complexes changed over the past four decades in the Hudson Plains? We present a distribution of permafrost peatlands (peat plateaus, palsas, and fen ridges) along a latitudinal transect and then discuss where along an adjacent transect peatland land cover has changed most. Finally, we present a conceptual classification map of permafrost peatland complexes susceptibility to permafrost-thaw-driven land cover and hydrologic change along a 285 km ´30 km latitudinal transect.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/998236

2022055974 Madani, Nima (Jet Propulsion Laboratory, Pasadena, CA) and Parazoo, Nicholas. Response of Arctic ecosystems to climate trends in the last two decades [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1450, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Terrestrial ecosystem productivity as the largest land-atmosphere annual carbon flux and the primary mechanism of creation of organic matter by plants, is critical component to reverse the impact of anthropogenic CO2 emissions. In this regard, carbon cycling in arctic and boreal ecosystems, which contain large carbon stocks and are rapidly changing, strongly impact Earth's climate-carbon feedback. The Arctic-Boreal zone in the last few decades has experienced widespread warming and coherent changes in various ecosystem components including land surface characteristics, vegetation productivity, hydrological cycles, permafrost thaw and fire disturbance. Recent observations and models suggest that summer carbon sequestration is becoming increasingly offset by release of carbon from soils due to warmer and dryer climate. Reduced carbon uptake during the peak of the growing season and increasing in fire activity could turn these biomes to a net carbon source. Here, we use a suite of satellite observation and models to assess the response of Arctic and boreal ecosystems to changes in climate in the last two decades.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/868267

2022059994 Manos, Elias (University of Connecticut, Department of Geography, Groton, CT); Hasan, Amit; Udawalpola, Mahendra; Liljedahl, Anna and Witharana, Chandi. Automated recognition of human-built infrastructure in the Arctic permafrost landscapes using commercial satellite imagery [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract U24A-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Very high spatial resolution (VHSR) commercial satellite imagery affords permafrost scientists the ability to monitor the pan-Arctic system at a fine-scale, enabling detailed monitoring of both the natural and human environments. Geo-AI mapping applications based on the deep learning (DL) convolutional neural network (CNN) have been successful in translating this big imagery resource into Arctic science-ready products. However, many models are computationally intensive due to the constraints of the large geographical extent and complexity of VHSR imagery. In addition, feature recognition is challenged by scarcity of manually-annotated training data and image complexity at fine scales. In this exploratory study, we investigated the ability of a lightweight U-Net DLCNN to efficiently perform semantic segmentation of VHSR commercial satellite imagery with limited training data in automated recognition of human-built infrastructure, including residential, industrial, public, commercial buildings, and roads, in the permafrost affected regions of the Arctic. We conducted a systematic experiment to understand how image augmentation improves the performance of DL-based semantic segmentation of VHSR imagery. Different standard augmentations, including flipping, rotation, and transposition, were applied to input imagery in order to test their impacts on infrastructure recognition and determine the optimal set of augmentations. With a relatively low number of model parameters, limited labelled training data, short training time, and high segmentation accuracy, our findings suggest that overall, the U-Net DLCNN, coupled with image augmentation, could serve as an accurate and efficient method for mapping infrastructure in the Arctic permafrost environment without compromising spatial details and geographical extent.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/919762

2022059924 Marchenko, Sergey S. (University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK); Jin Huijun and Luo Dongliang. The features of hydrologic and thermal regimes of coarse, blocky materials in high mountains, Central Asia and their impact on river runoff [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55E-0475, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Mountain permafrost and associated periglacial landforms contain large quantities of stored fresh water in the form of ice. The moraines, rock glaciers and other coarse debris and blocky materials have especially high ice content (sometimes more than 30-50% by volume). We conducted observations on seasonal ground ice accumulation and ablation inside of coarse debris, runoff, precipitation, and temperature dynamics in blocky materials of various genesis and altitudes. The mean annual temperatures inside of coarse debris are typically 3-5°C lower than mean annual air temperature. In such conditions, ice-rich permafrost may develop within coarse debris even in areas with mean annual air temperatures above 0°C. The result is an ice-block mass with ice content as high as 10-30% by volume. Over a warm season, the melted seasonal ice is an important portion in seasonal redistribution of the total river runoff. Knowledge gained in this study will improve the socio-economic vulnerability assessment of local communities whose livelihoods depend on the quantity and seasonality of water discharges of these mountain ecosystems.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/959458

2022056006 Matamala, Roser (Argonne National Laboratory, Environmental Science Division, Argonne, IL); Jelinski, Nicolas; Ping, Chien-Lu; Ainuddin, Irfan; Hoffmann, Scott; Lederhouse, Jeremy S.; Vugteveen, Timothy W. and Jastrow, Julie D. Soil properties, soil organic matter composition and vulnerability of Arctic hillslope catenas [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Hillslope landscape position contributes substantially to the uncertainty in estimates of soil organic carbon (SOC) stocks for permafrost regions. In particular, perennially frozen hill-toe soil deposits are one of the highest uncertainties at the circumpolar scale. Hillslope processes are impacted by the added complexity of permafrost-affected solifluction and other lateral mass movements, cryoturbation, and patterned-ground formation. The vulnerability of hillslope SOC stocks depends on ice contents and the amount and composition of soil organic matter occurring at different depths across the landscape. We are investigating how pedogenic processes in hilly terrains of the continuous permafrost zone affect soil properties, water/ice contents, and SOC stocks by sampling catenas formed on differing land surface ages in the Arctic Foothills of Alaska. Here, we compare results from catenas formed on loess over mid-Pleistocene till at Happy Valley and early-Pleistocene till at Sagwon Hills. Measurements include profile variations in texture, pH, soil organic matter composition (organic functional groups and minerals), SOC density, and water/ice contents at comparable hillslope positions for each catena. Seven hillslope positions (summit, shoulder, upper and lower backslope, upper and lower footslope, and basin) were sampled to depths of 1-3 m. Ice-wedges were observed at summit, shoulder, lower footslope, and basin positions, and ice-wedge polygons were clearly present in the basins but less so at other positions. Both hillslopes contained large SOC stocks across all positions to 1 m depth. Volumetric ice content was high across all positions with pore ice and ice lenses forming a range of soil cryostructures. Nevertheless, clear differences between the two catenas were observed. Although SOC concentrations in the toeslope and basin positions (particularly at deeper depths) were greater at Sagwon Hills than Happy Valley, several factors including greater ice contents affected SOC density, with greater SOC density in the first 1m of soil for these positions at Happy Valley than Sagwon Hills. Differences in soil organic matter composition and potential effects on the vulnerability of SOC stocks at different hillslope positions and between the two catenas will also be discussed.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/983558

2022057092 McClelland, James W. (University of Texas at Austin, Marine Science Institute, Austin, TX); Gurtovaya, Tatiana Yu.; Holmes, Robert Max; Scott, Lindsay; Moatar, Florentina; Shiklomanov, Alexander I.; Suslova, Anya; Spencer, Robert G.; Tank, Suzanne and Zhulidov, Alexander. Shifting biogeochemistry in Arctic rivers; patterns emerging from 17+ years of sampling by the Arctic Great Rivers Observatory [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP54A-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic Great Rivers Observatory (ArcticGRO, initiated as the PARTNERS project in 2003) was established to improve understanding of fluvial export from the six largest rivers draining the pan-Arctic watershed, and to define baselines against which future changes could be measured. Now, as we approach the 20 year mark for this project, remarkable patterns of change are emerging. This presentation highlights results from recent efforts to analyze trends within the ArcticGRO dataset and considers how observed changes in fluvial biogeochemistry relate to climate. Pan-Arctic changes in measurements such as alkalinity point to ubiquitous changes in hydrology (e.g. changes in precipitation regimes and water flow paths through soils as permafrost thaws) and associated mineral weathering. Changes in measurements such as stable isotope ratios of particulate nitrogen point to changes in organic matter sources and/or processing within the rivers. Seasonality, inter-annual variations, and natural modes of variability that oscillate at 5-10 year timescales make it challenging to isolate climate effects, but collective evidence from ArcticGRO suggests that widespread, long-term changes in Arctic river biogeochemistry are afoot. These changes have important implications for biogeochemical cycling and productivity within the Arctic Ocean.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/813786

2022056020 McDonough, Liza (Australian Nuclear Science and Technology Organization, Lucas Heights, N.S.W., Australia); Meredith, Karina; Saunders, Krystyna M. and Baker, Andy. Carbon cycling in sub-Antarctic and Antarctic lakes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1756, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Between 2000 - 2010, anthropogenic carbon emissions rose at rates of 2.2% year-1, a 70% increase above the annual rates observed between 1970 - 2000. This has accelerated global temperature increases. As a result, carbon fluxes to and from aquatic environments have changed, affecting microbial community compositions, and impacting the ability of some environments to act as carbon stores. Whilst the factors influencing nutrient cycling in many aquatic environments, including major rivers and oceans, have been well studied, little is known about the biogeochemical processes driving aquatic carbon cycling in sub-Antarctic and Antarctic lakes, and how this may be impacted by climate change. This is in part because sampling programs designed for such isolated environments take years to plan and require international collaboration. The isolation of these lakes however mean that many are relatively undisturbed by human activities, making them ideal locations to study the interactions between hydrological and biogeochemical processes, and the impact of climate change on natural carbon sources, transformation and storage. We aim to analyse Antarctic and sub-Antarctic lake water using organic carbon characterisation techniques such as fluorescence, liquid chromatography organic carbon detection and synchrotron characterisation, as well as radiocarbon and stable carbon isotopes of dissolved organic carbon (14CDOC and 13CDOC) and dissolved inorganic carbon (14CDIC and 13CDIC). This will allow us to identify key carbon sources such as terrestrial vegetation, groundwater and permafrost thaw, carbon age, and cycling via biodegradation or other processing mechanisms. The data collected for this project will form the first comprehensive spatial and temporal survey of dissolved carbon in both organic and inorganic phases in lakes across the region, aimed at understanding present-day environmental processes and their drivers. These data also have the potential to calibrate palaeo-records such as peat and lake archives which will assist in the understanding of the impacts of large-scale climate variability and environmental changes that may occur in the future.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/879073

2022055952 McSweeney, Killian (University of Georgia, Athens, GA) and Kooperman, Gabriel J. Influence of natural variability on simulated changes in Arctic permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A55N-1593, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic is especially vulnerable to climate change and is warming faster than the global average. Changes in this region pose a serious threat to the future of the planet due to the immense amount of methane and carbon dioxide frozen as organic material in the soil. If the frozen soil (i.e., permafrost) were to melt, it would release these gases into the atmosphere, leading to further warming. Permafrost thaw can also result in infrastructure damage that impacts many Arctic populations, and can disrupt the hunter-gatherer lifestyle many Arctic Indigenous Peoples rely on. A better understanding of potential changes and uncertainties in permafrost melt will inform climate adaptation or mitigation plans needed to prevent serious harm. This research project investigated projected changes in 21st century Earth system model simulations, based on a scenario of continued reliance on fossil fuels (RCP8.5). The study assessed changes to Arctic permafrost and focused on simulations from the National Center for Atmospheric Research's Community Earth System Model Large Ensemble experiment. We found that the vast majority of Arctic permafrost is completely lost by the end of the 21st century, but the exact timing varies across regions, and with soil depth. Natural variability plays a significant role in the timing of this melt, with a 10-20 year standard deviation in melt timing across most of the Arctic.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/964583

2022055988 Mekonnen, Zelalem A. (Lawrence Berkeley National Laboratory, Berkeley, CA); Riley, William J.; Bouskill, Nicholas; Shirley, Ian and Grant, Robert F. Wildfire accelerates carbon losses of high-latitude ecosystems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24E-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Historical Arctic and boreal forest soil organic carbon (SOC) decomposition is slower than plant growth, resulting in accumulated SOC trapped in permafrost. Anthropogenic climate warming has threatened this historical trend by accelerating SOC decomposition and altering the disturbance regime. Here we show that warmer climate and increases in wildfire may alter the net carbon balance of ecosystems across Alaska. We accurately modeled (compared with observations), the biomass and carbon emissions from wildfires across Alaskan ecosystems under the current climate. Future warmer climate and elevated atmospheric CO2 resulted in gains in plant biomass. However, increased carbon losses from (1) wildfire combustion, and (2) rapid SOC decomposition primed by the vegetation change, accelerated soil carbon turnover rate and led to soil carbon losses across Alaska. Our results show that projected wildfire and its subsequent effect on plant and soil carbon may accelerate high-latitude soil carbon losses resulting in positive feedback to the climate system.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/991110

2022055963 Mevenkamp, Hannah (University of Alaska Fairbanks, Fairbanks, AK); Euskirchen, Eugenie Susanne; Carman, Tobey; Serbin, Shawn; Genet, Helene; Wunderling, Nico; Winkelmann, Ricarda and Donges, Jonathan Friedemann. Reducing uncertainty of Arctic ecosystem models through identification of key parameters [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15A-1413, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Changes in vegetation and permafrost dynamics are altering carbon budgets and might push the Arctic from a carbon sink to a source. Yet, projections from terrestrial ecosystem models remain highly uncertain, limiting their relevance for climate change risk management. The significant mismatch between data availability and data needs for modeling leaves many parameters poorly constrained, and this parameter uncertainty then propagates through the models, making up a significant proportion of the output's uncertainty. Additional field samples of those parameters can thus be an efficient way to refine Arctic ecosystem models. For this study, we compared three models, DVM-DOS-TEM, ED2, and SiPNET, to evaluate how model structure can impact parameter uncertainty. To identify which parameters should be prioritized in field efforts, we identify the mismatch between data needs and data availability in various databases, including the TRY Plant Trait Database, the Biofuel Ecophysiological Traits and Yield database (BETY), the Arctic Long Term Ecological Research database (LTER), the Next-Generation Ecosystem Experiments Arctic data catalogue (NGEE Arctic), and the Fine-Root Ecology Database (FRED). To further refine which parameters to target, we compare the models to a causal loop diagram of the Arctic ecosystem, which includes unquantified, and thus unmodeled, processes. We map model parameters to processes in the causal loop diagram and identify important feedbacks via the internal network structure. One important network substructure, the so-called feed forward loops, quantify processes that are linked through both a direct and an indirect process, via one intermediary variable. These indirect processes might be implicitly included in the model if parameter values are accurately depicting field conditions. We find that the parameters related to minimum and optimum temperature for photosynthesis are associated with a particularly high number of feed forward loops, but are not constrained well by existing data. Through both methods combined, i.e. the identification and use of parameters from the databases and analysis in the causal loop diagram, we identify which model parameters play a key role in model precision and should be prioritized for further sampling in the field to reduce model uncertainty.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/811265

2022057041 Mitchell, Raven Jezell (Michigan State University, East Lansing, MI); Klene, Anna E.; Shiklomanov, Nikolay I.; Nyland, Kelsey E.; Streletskiy, Dmitry A. and Nelson, Frederick E. Snow-cover effects on the active layer above permafrost; results of long-term ground surface temperature observations in northern Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0941, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Snow cover impacts the permafrost system through insulative effects. Snow cover is spatially variable in areas affected by permafrost, owing to heterogeneous vegetation types, local topography, and redistribution by wind. Snow depth measurements are difficult to collect over large areas and monitoring sites are sparse in permafrost-affected regions. Long-term (>20 yr) active layer thickness (ALT) and temperature (ground and air) monitoring stations are maintained by the Circumpolar Active Layer Monitoring (CALM) program across Arctic Alaska. CALM records show that summer temperature records cannot fully explain the observed long-term active layer trends. Discrepancies between ALT and summer temperature trends indicate that winter dynamics, specifically snow cover, play an important role in permafrost-climate interactions in this region. We present long-term air and ground-surface temperatures, snow depth, and snow period duration trends employed to explore wintertime characteristics with respect to ALT dynamics. Monthly snow depth and winter precipitation data from SNOTEL sites near CALM sites (Prudhoe Bay, Imnavait Creek, Sagwon) were used in conjunction with snow cameras (located at CALM sites) as indicators for snow cover. Preliminary results show increasing differences in ground surface and air temperatures. Snow cover duration data from three CALM sites show a decreasing trend from 2013-2019. SNOTEL monitoring site records show stability or decreasing trends in snow depth and increasing trends in accumulated precipitation. The results of this work help to better characterize the impacts of heterogenous snow cover on the permafrost system and cast new light on ALT trends not easily explained by summer temperatures alone.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/977883

2022055956 Moritz, Hannah Holland (University of New Hampshire, Durham, NH); Cronin, Dylan R.; Aroney, Sam; Woodcroft, Ben J.; Tyson, Gene W.; Rich, Virginia Isabel and Ernakovich, Jessica Gilman. Assembly of microbial communities in thawing permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B11D-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic permafrost soils store one third of the world's soil carbon and amplified Arctic warming is resulting in permafrost thaw. Permafrost thaw allows microorganisms to access previously unavailable soil organic matter and release greenhouse gases through decomposition. The rate and type of greenhouse gases released during decomposition depends on thaw-induced changes in microbial community structure and functional capacity. However, predicting these community changes and the subsequent carbon release is challenging as changes in community structure - collectively known as assembly - are the result of a combination of eco-evolutionary and environmental processes, some of which can be directly predicted through species identity ("deterministic" forces) and others which are random with respect to species identities ("stochastic" forces). Due to the potential for hysteresis during community assembly and compounding perturbations to communities over time, predicting the multi-year effects of thaw on communities is particularly challenging without first understanding which deterministic and stochastic forces are in play. However, this mechanistic understanding of community assembly is vital to design more accurate predictive models of permafrost carbon dynamics. To better understand how the ecological processes structuring these microbial communities and their functions change over time, we used shotgun metagenomic sequencing to investigate the changes in active layer soil microbial communities over six years (2011 - 2017) along a permafrost thaw gradient in Stordalen Mire, near Abisko Sweden. We then used ecological models to identify processes governing assembly and found that soils experienced a transition from homogenizing to heterogeneous selection as permafrost thawed, and that habitat-specific selection increased across years. These results, suggest a switch from abiotic pressure to competition during thaw which became more pronounced from 2011 to 2017. We also identified genes and organisms most associated with selective forces and thus most likely to be affected in thawing permafrost. The results from this study give us a better idea of the ecological forces driving post-thaw community assembly, and will help us better predict carbon dynamics in thawing permafrost ecosystems.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/991346

2022055948 Mudryk, Lawrence (University of Toronto, Department of Physics, Toronto, ON, Canada); Burke, Eleanor; Krinner, Gerhard; Collier, Nathan; Derksen, Chris and Lawrence, David M. Simulation of cold processes in the CMIP6 land-historical simulations [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A45F-1903, 4 ref., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Model evaluation is a necessary component of climate research. While the snow and soil components of land-surface models have been previously evaluated using standalone simulations (Dirmeyer et al., 1999; Slater et al., 2001; Dirmeyer, 2011), the Land Surface, Snow and Soil moisture Model Intercomparison Project (LS3MIP; van den Hurk et al., 2016) is the first CMIP framework that coordinates both components and integrates them into the larger suite of CMIP experiments. Here we analyze output from the "offline" global land surface simulations, forced by historically observed meteorological conditions, and compare them to the fully coupled and AMIP historical CMIP6 simulations. In this context, we focus on high-latitude processes and variables, in particular snow and permafrost. We demonstrate that there are marked differences in the representation of snow between the coupled and "offline" simulations, in both their climatological extent and total mass, as well as their variability. For snow, differences in the balance of accumulation and ablation between the coupled and uncoupled simulations yield differences in climatological snow extent and snow mass. However, these differences do not mar the representation of historical snow variability. The strong influence of driving temperature and precipitation variability results in a clear improvement of historical snow variability in the "offline" simulations for both long term trends and interannual variability. For permafrost, errors in the functional relationships that control permafrost extent and soil temperature are large and much more important than differences due to improved representation of historical temperature, precipitation or other meteorological drivers. These differences suggest that the added value of standalone land model simulations in the suite of CMIP6 experiments will depend on the land-model variable of interest. References: Dirmeyer (2011), URL: https://doi.org/10.1175/JHM-D-10-05010.1 Dirmeyer et al. (1999), URL: https://doi.org/10.1175/1520-0477(1999)0802.0.CO;2 Slater et al. (2001), URL: https://doi.org/10.1175/1525-7541(2001)0022.0.CO;2 van den Hurk et al. (2016), URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/832480">https://doi.org/10.5194/gmd-9-2809-2016

https://agu.confex.com/agu/fm21/meetinga ...

2022059922 Mutter, Edda A. (Yukon River Inter-Tribal Watershed Council, Anchorage, AK); Kholodov, Alexander L. and Elder, Kelly. Effect of the deepening of driven active layer on the hydrology and hydrochemistry within the Yukon River basin [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC52C-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Yukon River Basin (YRB) is underlain by discontinuous and sporadic permafrost zone, a landscape ecologically most fragile to a warming climate. The Indigenous Observation Network (ION) is a partnership between the Alaska Native Tribes and First Nations, the Yukon River Inter-Tribal Watershed Council (YRITWC), the United States Geological Survey (USGS), the United States Forest Service (USFS), and the University of Alaska, Fairbanks (UAF) that combines local environmental observation and physical science to address concerns with regards to past and current changes to the landscape and hydrology. The community-based research program has developed two projects that focus on the greater integration of hydrology, fluvial biogeochemistry and seasonal active layer dynamics. The Active Layer Network (ALN) has been established following the Circumpolar Active Layer Monitoring program protocol since 2009, to measure physical active layer depth as well as soil moisture, soil temperature, and air temperature sensor data collection at 18 sites across the YRB. The active layer is defined as the top layer of soil that thaws during the summer and freezes again during the autumn. In this presentation, we will discuss the influence of active layer dynamics processes on changes in discharge and groundwater contribution and, eventually, water quality. Leveraging historical data from the USGS and ION over the past decade hydrological active layer trend analysis show correlation between the increase of annual fluxes of weathering ions, Dissolved Organic Carbon (DOC) and O18 and the increase of active layer thickness across the YRB. Additionally, we highlight the ION monitoring efforts to assist Alaska Tribes and Yukon First Nations to assess and to develop climate adaptation and water governance strategies to mitigate effects on freshwater systems, food security, and both human and ecosystem health.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/976611

2022059946 Nair, Akhilesh Sivaraman (Indian Institute of Technology Bombay, Department of Civil Engineering, Mumbai, India); Indu, J. and Semenova, Olga. Improving land surface seasonal dynamics in permafrost areas by using soil moisture assimilation [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H35W-1295, 2 ref., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Soil moisture (SM) is an important component of land surface dynamics, exerting a substantial impact on the interchange of water and energy fluxes between land and atmosphere. SM modelling over frozen regions remains challenging. Despite the fact that satellite measurements provide reliable SM estimates, the improved capability of land data assimilation in the permafrost zone is unknown. This study investigates the possibility of satellite SM assimilation to enhance LSM seasonal dynamics by utilizing blended SM from the European Space Agency's Climate Change Initiative. The Noah LSM model is used in this work because of its capacity to capture the influence of SM on soil thermodynamics and surface energy balance. [Nair and Indu, 2016; 2019]. The Ensemble Kalman Filter (EnKF) technique is used to integrate the SM observation across the Iya River basin (in South-Eastern Siberia, Russia), that has a catchment area of 14500 sq. m. Because the area is plagued by permafrost, only the summer season (June to August) is used for assimilation (June to August). Results of this study are validated with field measurements from two stations. Assimilation reduces the dry bias in Noah LSM by up to 6%, which is particularly evident in the Iya basin's north region. Furthermore, the results show a significant improvement in correlation between SM after assimilation (0.94) and before assimilation (0.84) with respect to station observations. The results also show a strong coupling between SM and surface energy balance, allowing assimilation to lower the sensible heat flow across the river basin's northern section.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/853644

2022056005 Natali, Susan (Woodwell Climate Research Center, Falmouth, MA); Rogers, Brendan M.; Bronen, Robin; Clement, Joel; Duffy, Phil; Fiske, Greg; Genet, Helene; Jafarov, Elchin; Holdren, John P.; MacDonald, Erin; Peter, Darcy; Pomerance, Rafe; Potter, Stefano; Treharne, Rachael; Virkalla, Anna and Watts, Jennifer. Incorporating permafrost into climate mitigation and adaptation policy and action [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The arctic and boreal regions are warming at more than twice the global rate, with temperatures already greater than 2°C above preindustrial levels. Rapid warming is intensifying wildfires and thawing permafrost, both of which are transforming northern ecosystems and creating hazardous conditions that are forcing arctic communities to make difficult and urgent adaptation decisions. These changes can also impact global climate through carbon feedbacks, and thus there is an urgent need to reduce the uncertainties that observational and modeling gaps create in understanding the current and future state of permafrost feedbacks. Despite this need, at present, not even current scientific understanding of future emissions from a warming Arctic is reflected in most climate policy planning. Carbon emissions from thawing permafrost and intensifying northern wildfires present a major challenge to meeting the Paris Agreement's already difficult goal of holding the global average temperature increase to well below 2°C above preindustrial levels. We present a synthesis of current knowledge gaps and uncertainties in permafrost science in the context of regional to global policy initiatives and describe an approach for integrating permafrost science into climate mitigation and adaptation policy and action. This approach includes strategic monitoring of current carbon fluxes to address critical knowledge gaps across the arctic and boreal regions; comprehensive modeling guided by stakeholder needs and that includes key processes (e.g., abrupt and fire-induced thaw) at relevant spatial and temporal scales; co-production of an Arctic community-led adaptation process that protects the human rights of climate threatened communities; and coordination between science outputs and policy needs. While more observational data and model improvements are needed, these scientific advances alone will not lead to appropriate action without coordinated and intentional communication between scientific communities, Arctic residents, and policy makers. A strategic commitment to engaging with relevant audiences requires time and resources but, in return, will result in more effective transfer of knowledge and, ultimately, more effective climate change policies that are urgently needed to address the global climate crisis.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/934832

2022059933 Nelson, MacKenzie (American Geophysical Union); Shaban, Mirella; Epstein, Howard E.; Cho, Leena; Douglas, Thomas A.; Griffin, Claire G.; Cooke, Aaron; Jull, Matthew G.; Murillo, Luis Felipe Rosado; Nelson, Lars and Wylie, Caitlin D. Understanding the changing natural-built landscape in an Arctic community; an integrated sensor study in Utqiagvik, Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55J-0532, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Utqiagvik, Alaska is home to thousands of residents, including the native Inupiat who have occupied the land for thousands of years. Thawing permafrost and anthropogenic changes to the landscape are altering the Arctic tundra from its current conditions. A critical question for sustainability is - How are the built and natural environments interacting in the context of climate change to affect natural system components, such as land-atmosphere exchange and hydrochemistry? As part of an NSF Navigating the New Arctic project, academic and applied researchers are collaborating with community participants in Utqiagvik to answer this critical question, and to better project the on-going complexities of these systems and inform plans for the future of Arctic communities. The proposed project methodology includes deployment of complementary terrestrial micro-meteorological and aquatic sensors coupled with geotechnical surveys throughout the community to assess the interactions of the urban infrastructure with surrounding air, ground, and water systems. The terrestrial sensor network array will be a twenty-station deployment across multiple coastal and urban transects in Utqiagvik intended to create a comprehensive picture of environmental variations throughout the community. Combined terrestrial sensor network and geotechnical survey transects conducted by CRREL (Cold Regions Research and Engineering Laboratory) will explore the connections among infrastructure, tundra, and permafrost. The aquatic sensor network will monitor key water resources in Utqiagvik, with a focus on the changing hydrologic connectivity of water bodies with urban infrastructure development. Stand-alone aquatic sensors will be placed in fifteen ponds and three multi-parameter sondes will be deployed in nearby lagoon systems of the city to measure temperature, water depth, conductivity, and additional hydrochemistry parameters. With continued climate variability and urbanization, Utqiagvik faces increased vulnerability at the intersection between natural and built systems. The multi-disciplinary collaboration of environmental scientists, architects, data scientists, social scientists, and Arctic residents in our study will co-produce informed and accessible knowledge of the transforming Arctic landscape.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/893640

2022059923 Newman, Andrew James (National Center for Atmospheric Research, Hydrometeorological Applications Program, Boulder, CO); Cheng, Yifan; Musselman, Keith N.; Craig, Anthony; Swenson, Sean C.; Hamman, Joseph and Lawrence, David M. High-resolution regional climate simulations of Alaskan hydroclimatic change [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55A-0408, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic has warmed during the recent observational record and is projected to keep warming through the end of the 21st century in nearly every future emissions scenario and global climate model. This will drive continued thawing of permafrost-rich soils, alter the partitioning of rain versus snow events, and greatly affect the water cycle and land-surface processes across the Arctic. However, previous analyses of these impacts using dynamical models have relied on global climate model output or relatively coarse regional climate model simulations potentially limiting process understanding and change representation. Here, we discuss recent work examining high-resolution (4 km grid spacing) regional climate simulations over Alaska and NW Canada. Simulation results are very encouraging and show the regional climate model yields a realistic representation of the seasonal and spatial evolution of precipitation, temperature, and snowpack compared to previous studies across Alaska and other Arctic regions. A paired future climate simulation using the Pseudo-Global Warming approach shows large changes in major components of the hydroclimate (e.g. precipitation, temperature, snowpack). For example, the seasonal snow cover in some regions is projected to mostly disappear. However, there are also projected increases in snowpack in historically very cold areas that are able to stay cold enough in the future. Finally, we will present a new project to couple an advanced land-surface model, the Community Terrestrial Systems Model (CTSM), within the Regional Arctic Systems Model (RASM) in an effort to better represent complex land-surface and subsurface (e.g. permafrost, streamflow availability timing and temperatures) processes for climate change impact studies. CTSM is a complex physically based land-surface model that is able to represent multiple snow layers, a complex canopy, and multiple soil layers including organic matter and frozen soils, which enables us to explicitly represent spatial variability in the regional hydroclimate and land states (e.g. permafrost) at relatively high spatial resolutions relative to other simulations (4 km land and atmosphere grids). Successful coupling of CTSM within RASM has been completed and we will discuss some preliminary land-atmosphere coupled test results.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/959931

2022057040 Nicolsky, Dmitry (University of Alaska Fairbanks, Fairbanks, AK); Farquharson, Louise Melanie; Romanovsky, Vladimir E.; Douglas, Thomas and Schmidt, Jennifer. Permafrost hazard mapping in the discontinuous permafrost zone of Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0940, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost degradation is expected to cause extensive damage to infrastructure across the Arctic and sub-Arctic in coming decades. This poses a hazard to both communities and industry and is expected to result in significant economic impacts. Permafrost degradation can lower the bearing capacity of soils leading to the failure of building foundations, and where excess ground ice is present can lead to ground collapse and water ponding. Hazard maps for both the present and future can potentially assist communities in hazard mitigation and adaptation. Here we present hazard maps for the Fairbanks North Star Borough (FNSB), interior of Alaska. To establish a current (2020) hazard map for the FNSB we combined a suite of data sets to characterize both the distribution and cryolithological characteristics of permafrost across the Borough. Data sources included existing non-digitized permafrost maps, Department of Natural Resources well logs, Department of Transportation boring logs for road alignments, and an array of ground temperature station measurements from several entities including the U.S. Army Cold Regions Research and Engineering Laboratory, and numerous research groups from the University of Alaska Fairbanks. For the 2050 hazard mapping we employed a high-resolution ecotype-based numerical model of the temperature dynamics. Model parameters, such as thermal properties, were estimated using collected temperature measurements and were upscaled using 30-m resolution vegetation maps derived with the scope of the NASA Arctic Boreal Vulnerability Experiment (ABoVE) initiative. Temperature dynamics, talik development and the potential for thermokarst degradation is estimated for IPCC Representative Concentration Pathway scenarios 4.5 and 8.5. The modelling results show wide spread talik formation across the region in 2020-2030, which is corroborated by present-day observations. Warming permafrost, potential ground subsidence, and the development of taliks will have serious implications for ecosystems, human activities, and potential feedbacks to climate change. The permafrost characteristic maps that we have developed are sought to provide guidance to homeowners and borough planners about the present and future permafrost conditions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/979306

2022057004 Nitze, Ingmar (Alfred Wegener Institute Helmholtz Center for Polar and Marine Research Potsdam, Potsdam, Germany); Heidler, Konrad; Barth, Sophia; Grosse, Guido and Targowicka, Aleksandra. Evaluating a deep-learning approach for mapping retrogressive thaw slumps across the Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B51B-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Retrogressive thaw slumps (RTS) are typical landforms indicating processes of rapid thawing and degrading permafrost. Their abundance is increasing in many regions and quantifying their dynamics is of high importance for assessing geomorphic, hydrologic, and biogeochemical impacts of climate change in the Arctic. Here we present a deep-learning (DL) based semantic segmentation framework to detect RTS, using high-resolution multi-spectral PlanetScope, topographic (ArcticDEM elevation and slope), and medium-resolution multi-temporal Landsat Trend data. We created a highly automated processing pipeline, which is designed to allow reproducible results and to be flexible for multiple input data types. The processing workflow is based on the pytorch deep-learning framework and includes a variety of different segmentation architectures (UNet, UNet++, DeepLabV3), backbones and includes common data transformation techniques such as augmentation or normalization. We tested (training, validation) our DL based model in six different regions of 100 to 300 km2 size across Canada, and Siberia. We performed a regional cross-validation (5 regions training, 1 region validation) to test the spatial robustness and transferability of the algorithm. Furthermore, we tested different architectures, backbones and loss-functions to identify the best performing and most robust parameter sets. For training the models we created a database of manually digitized and validated RTS polygons. The resulting model performance varied strongly between different regions with maximum Intersection over Union (IoU) scores between 0.15 and 0.58. The strong regional variation emphasizes the need for sufficiently large training data, which is representative of the diversity of RTS types. However, the creation of good training data proved to be challenging due to the fuzzy definition and delineation of RTS. We are further continuing to improve the usability and the functionality to add further datasets and classes. We will show first results from the upscaling beyond small test areas towards large spatial clusters of extensive RTS presence e.g. Peel Plateau in NW Canada.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/966053

2022059957 Nitze, Ingmar (Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research, Potsdam, Germany); Tang, Hui and Grosse, Guido. How to discover an unknown mega-landslide in the Siberian Far-East [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NH33A-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Using our custom visualization tool for multitemporal Landsat satellite imagery we discovered, to our knowledge, an undocumented mega-landslide in far-east Siberia, which occurred in summer 2017 (URL: https://bit.ly/2WYRLM1; 61.55°N; 170.01°E). To create and visualize this unique dataset, we processed temporal trends of multispectral indices of >100,000 Landsat images for a period from 2000-2019 using the freely available Google Earth Engine cloud processing platform (URL: https://ingmarnitze.users.earthengine.app/view/hotspottcvisapp). The megaslide has a size of 3.66 km2 and using the ArcticDEM data we estimate a volume movement of ~20 Mm3. With this size and volume, the landslide is among the largest globally known in recent decades. The landslide is accompanied by a smaller one (0.31 km2, 1 Mm3) about 600 m further east, which already occurred in summer 2015. The large landslide caused the formation of several small lakes by blocking two valleys with debris and within newly formed crevasses near the hilltop, which are still persisting as of August 2021. As this event occurred in a remote valley far from any settlement, no visible damage to infrastructure or human livelihoods was detected. The remoteness has likely led to being not detected, like many similar, albeit a lot smaller, erosion features in the Arctic permafrost region. In this presentation we will show the main properties of the landslide, potential trigger mechanisms in the traditional sense. As this region is located along the fringes of permafrost presence we will discuss its potential connection to the rapidly warming climate in the high latitudes. Further, we will discuss how such a large event remained undetected for several years. We discuss and highlight the value of our landscape change visualization tool based on Landsat trend analysis (see Nitze et al., AGU 2020), which helped us to identify this extreme event. With more and more available data sources, this tool in addition to automated image analysis (e.g. deep-learning) or seismic analysis will help to uncover the hidden processes and dynamics of the Earth's surface.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/968107

2022057015 Nyland, Kelsey E. (George Washington University, Washington, DC); Streletskiy, Dmitry A.; Shiklomanov, Nikolay I.; Nelson, Frederick E.; Klene, Anna E. and Moore, Nathan J. Long-term trends from the Circumpolar Active Layer Monitoring (CALM) program [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C22C-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The World Meteorological Organization's Global Climate Observing System (GCOS) identified active layer thickness (ALT) as an essential climate variable for understanding and modeling natural processes in cold regions. The standardized monitoring of ALT in representative landscapes of the Arctic, Antarctic, and high-elevations of the mid-latitudes is the primary objective of the Circumpolar Active Layer Monitoring (CALM) program, a component of the GCOS Global Terrestrial Network for Permafrost (GTN-P). The CALM program is a collaborative network of researchers from 15 countries who have maintained these ALT monitoring sites since 1991. This presentation provides a synthesis of long-term ALT trends based on central tendencies of CALM sites from major monitoring regions of the Arctic, Antarctic, and alpine mid-latitudes. Only sites with a minimum of 10 consecutive years of data that have reported within the last four years were included in this analysis. CALM data from around the world show variable, but generally thickening active layer trends. The greatest rates (>10 cm/yr) were observed in bedrock sites in the European Alps. The majority of sites in unconsolidated sediments in the Arctic showed trends from 0.2 to 3.5 cm/yr. The greatest positive trends were observed in the Russian European North and Northwest Siberia and the lowest on the Alaskan North Slope. Antarctic regions showed minor to insignificant trends. Globally increasing ALT trends have major implications for the functioning of Arctic hydrology, geomorphic processes, ecosystems, and human settlements, which confirms the need for continued and expanded observation.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/975222

2022057068 Ohara, Noriaki (University of Wyoming, Department of Civil and Architectural Engineering, Laramie, WY); Jones, Benjamin M.; Parsekian, Andy; Hinkel, Kenneth M.; Yamatani, Katsu; Kanevskiy, Mikhail Z.; Rangel, Rodrigo Correa; Breen, Amy Lynn and Bergstedt, Helena. Optimal talik geometry under thermokarst lake in quasi equilibrium state in Arctic Coastal Plain [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Geomorphology in arctic tundra is considered one of the key processes that influences the global carbon cycle under evolving climate, particularly due to the role of thermokarst lakes in thawing permafrost. Here we introduce a new variational principle that determines the optimum thermokarst lake thaw bulb "talik" geometry in the continuous permafrost region under quasi-equilibrium state. We found that the three-dimensional (3D) Stefan equation beneath a thermokarst lake should be in the form of a semi-ellipsoidal function using functional analysis. The Euler equation in the calculus of variations was analytically solved for an extremum of the functional describing the phase boundary area with a fixed total talik volume. We show that the semi-ellipsoid geometry of the talik minimizes the total permafrost thaw under the lake for a given annual heat input. The derived 3D Stefan equation also serves to relate the talik width-depth ratio and the vertical temperature gradient under the lake. This may be one of main reasons that oval shaped lakes are widespread across the Arctic Coastal Plain (ACP), although the lake cross-sectional bathymetry tends to be a flat-bottomed rectangular (less elliptic) due to the presence of near-surface ice-rich layers in the permafrost. We successfully verified the model by comparing predicted talik geometry below Peatball Lake on the ACP of Alaska against transient electromagnetic (TEM) geophysical field data. We also reviewed existing hypothetical models in the literature to determine the applicability of the 3D Stefan equation for thermokarst lake characterizations including lake orientation. Incoming solar radiation energy inequality on the sloped lake bank was found to be marginal compared to wind wave and wind-induced current effects on lake elongation. However, thaw subsidence due to talik development may diminish the wind-wave effect as suggested by the remotely-sensed lake geometry statistics. This study combining theory and observation suggests that wind-induced waves and currents are likely responsible for the elongation and orientation of thermokarst lakes while talik development stabilizes thermokarst lakes by ground subsidence due to permafrost thaw in the ACP of northern Alaska.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/905065

2022057052 Olefeldt, David (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Aragones, Cristian Estop; Harris, Lorna I.; Heffernan, Liam; Kuhn, McKenzie Ann; Marouelli, Kate; Schulze, Christopher; Shewan, Renae; Tanentzap, Andrew and Thompson, Lauren. Impacts of permafrost thaw on the biogeochemistry of boreal peatland complexes; accounting for all ecosystem transitions [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Boreal peatlands are widespread in the discontinuous permafrost zone, and have accumulated vast stores of peat during the Holocene. Rapid ongoing permafrost thaw is re-organizing the hydrology and ecology of these peatlands, causing relatively dry, forested peat plateaus to collapse and transform into bogs, fens, and ponds. These transitions have drastic implications for the biogeochemical processes controlling the greenhouse gas exchange, but also the downstream export of solutes such as dissolved organic matter and methylmercury. To study the implications of thaw, we have studied thermokarst bogs, fens, and ponds within peatland complexes in boreal western Canada. In this region, permafrost aggraded ~1,500 to 4,000 years ago, so a majority of the peat stores had already accumulated prior to permafrost aggradation. We find that development of thermokarst bogs leads to increased methane emissions but more or less neutral carbon balance, and very little aged dissolved organic carbon is exported downstream. Elevated methane emissions during the early bog stage are driven by both thermal regimes and microbial communities. The thermokarst fens have greater variability in environmental conditions and vegetation composition than the bogs, due to variable groundwater influence - but have generally greater potential for both higher methane emissions and the production and downstream mobilization of methylmercury. Thermokarst pond expansion led to the highest observed methane emissions, driven primarily by ebullition of millennial-aged methane. Our research shows that it is crucial to account for all ecosystem transitions within boreal peatlands in order to understand the overall impact of permafrost thaw on carbon cycling and downstream water quality.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/794120

2022055953 Opfergelt, Sophie (Catholic University of Louvain, Department of Environmental Sciences, Louvain-La-Neuve, Belgium); Hirst, Catherine; Mauclet, Elisabeth; Monhonval, Arthur; Thomas, Maxime; Gaspard, François; Villani, Maëlle and Dailly, Hélène. Changing conditions for mineral-organic carbon interactions across the permafrost landscape; hot moments more than hot spots? [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B11B-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Earth's high latitude regions are warming twice as fast as the global average which enhances the thawing of permafrost. According to geological archives, abrupt thaw and thermokarst formation in the past have induced changes in redox conditions in ice-rich permafrost deposits, affecting iron distribution and interactions between organic carbon and iron (Monhonval et al. 2021), modifying thereby the protective role of minerals for organic matter. This example illustrates that the evolution of mineral-organic carbon interactions with permafrost thaw is a potentially important player in the modulation of permafrost carbon emissions. The stability of mineral surfaces and the availability of metal ions for binding organic carbon are likely to vary upon changing water saturation in response to permafrost thaw and deepening of the active layer. Using the distribution of mineral elements with direct (Fe) or indirect (Si) interactions with organic carbon, we investigate the changing conditions for mineral-organic carbon interactions on a variety of scales across the modern permafrost landscape. Our results show that at the pedon scale localized freeze-thaw events occurring during the winter period create hot moments for soil biogeochemical reactions in microenvironments (»10 to 20 cm thick soil layers) and that these reactions affect the solute transfer from soils to rivers. Our data also support that hot spots for biogeochemical reactions are created in the novel active layer resulting from thermokarst slump deposits upon abrupt thaw. The temporal and spatial heterogeneity in the distribution of unfrozen soil microenvironments in the permafrost landscape is more complex than previously thought. The role played by ice and frost at structuring and compartmentalizing microenvironments hosting mineral-organic carbon interactions in permafrost soils should be seen as more variable seasonally and spatially. Monhonval et al. 2021. Iron redistribution upon thermokarst processes in the Yedoma domain. Front. Earth Sci. 9, doi.org/10.3389/feart.2021.703339.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/801733

2022057080 Overeem, Irina (University of Colorado at Boulder, Boulder, CO); Piliouras, Anastasia and Nienhuis, Jaap. Arctic deltas are ice-dominated; development of a quantitative descriptor of ice as a process control [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP31B-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic deltas form a critical interface between the Arctic terrestrial domain and the global oceans. They filter freshwater, sediment, and carbon fluxes from ~14 million km2 of permafrost terrain. We postulate that Arctic deltas are 'ice-dominated systems', affected by both permafrost and sea ice in their modern morphodynamic behavior. Arctic deltas' controlling river and marine processes are strongly seasonal, with frozen, dormant conditions dominating for 7-9 months. Permafrost limits channel migration even during the active months, because channel bank erosion requires thermo-incision of frozen, highly cohesive banks. When river flood water arrives in the spring melt season, land-fast sea ice is still present in many Arctic deltas. Under ice transport creates shallow prodelta ramps that are not found in temperate or tropical deltas, representing a unique feature of ice covered deltas. Open-ocean conditions promoting marine reworking of river deposits only last for a few months in the fall. We capture 'ice-dominance' of the processes in a metric that quantifies the time-window of overlap between early season river flood arrival, sea ice presence, and permafrost abundance. We use a coupled model-data compilation of continental Arctic deltas and find that present sediment and carbon fluxes are substantially lower than for lower latitude deltas. Arctic delta morphodynamics are also markedly subdued, with about 8-fold less land-water conversion in the active river mouth regions. This may be explained by the unique ice processes in Arctic deltas, which result in preferential floodplain and submarine sedimentation. Future trajectories of controlling factors indicate that Arctic deltas will transition away from ice-dominance. Permafrost thaw is a slow process, but model projections show doubling of the active layer depth, which may be most impactful in delta distributary networks, where bank heights are lower. The open water season is expanding rapidly, with a 3-fold increase in wave energy expected by 2100. Arctic deltas will thaw and experience increased wave influence, with poorly understood consequences for delta morphodynamics and carbon cycling. Process studies under current transitional conditions are needed to further develop predictive models.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/955855

2022055983 Pan, Naiqing (Auburn University, International Center for Climate and Global Change Research, Auburn, AL); Tian, Hanqin; Pan, Shufen; Shi, Hao; Canadell, Josep Gili; Chang Jinfeng; Ciais, Philippe; Davidson, Eric A.; Hugelius, Gustaf; Ito, Akihiko; Jackson, Robert B.; Joos, Fortunat; Millet, Dylan B.; Olin, Stefan; Patra, Prabir Kumar; Thompson, Rona; Wells, Kelley C.; Wilson, Chris J. and Zaehle, Sönke. Increased soil N2O emissions from the Arctic-boreal region; non-negligible non-carbon climate feedback [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24B-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Nitrous oxide (N2O) is a potent greenhouse gas with 298 times the global warming potential (GWP) of CO2 on a 100-year time horizon. Atmospheric N2O burden significantly increased since the preindustrial period, mainly because of the enhanced soil N2O emissions. The Arctic-Boreal region stores about half of the global soil N stock, and undergoes amplified climate change which enhances N mineralization and promotes nitrification and denitrification. Moreover, warming leads to permafrost loss, as a result, large quantities of previously frozen soil N stocks become substrate for N2O production. However, this non-carbon climate feedback hasn't been studied at the regional scale. Here, we quantifies historical soil N2O emissions from the Arctic-Boreal region using process-based ecosystem models and disentangles the contributions of different driving factors by setting a series of simulation experiments. Our results show that N2O emissions from the Arctic-Boreal region (north of 50°N) increased by 82% since the 1860s. Climate change was a major driver, contributing to 37.2% of the increase, and it made a larger contribution in permafrost-affected regions. Although both temperature and precipitation play important roles in regulating local soil N2O emissions, temperature made a larger contribution to the increase of total emissions than precipitation, likely because warming is more pronounced and spatially prevalent. Atmospheric inversion models yield generally comparable spatial pattern of N2O emissions with that of bottom-up approach, but give lower estimations of regional total emissions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/996407

2022055965 Park, Hansu (Seoul National University, School of Earth and Environmental Sciences, Seoul, South Korea); Ko, Nayeon; Kim, JeongEun; Opel, Thomas; Meyer, Hanno; Wetterich, Sebastian; Fedorov, Alexander; Shepelev, Andrei G. and Ahn, Jinho. Gas compositions and origins of greenhouse gas in permafrost ice wedges at Batagaika megaslump, Yana Uplands, northeast Siberia [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15B-1424, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Batagaika megaslump (Yana Uplands, Northeast Siberia) exposes a massive stratigraphy with two ice complexes. Previous studies suggest the ages as MIS4-2 and MIS16 for the Upper and Lower Ice Complexes, respectively. In this study, we present gas compositions (O2, N2, Ar, CO2, CH4, and N2O) of air bubbles entrapped in the permafrost wedge ice of both ice complexes. We extracted gas in bubbles by both wet and dry extraction methods. Then, the mixing ratios were analyzed using gas chromatography. The d(N2/Ar) values range from -8.06% to 33.86% for the Lower Ice Complex and -5.49% to 30.64% for the Upper Ice Complex. The d(N2/Ar) values indicate that there is little melting during and after the ice complex formation, which is also supported by investigation of the bubble shapes. On the other hand, the d(O2/Ar) values range -89.01 to -67.43% and -98.07 to -47.06% for the Lower and Upper Ice Complexes, respectively. Highly depleted d(O2/Ar) values may indicate strong oxidation reactions by microbial activities and/or abiological oxidation reactions. CO2, N2O, and CH4 concentrations are highly variable. We observe CO2 concentrations of 1.9-10.3%, N2O of 0.1-8 ppm, and CH4 of 30-170 ppm for the Lower Ice Complex, while CO2 of 0.03-8.89%, N2O of 0.3-70 ppm, and CH4 of 5-980 ppm for the Upper Ice Complex. The high N2O concentration in the Upper Ice Complex is distinctive compared with other permafrost regions. The CH4 shows a weak negative correlation with N2O in both ice complexes. Our future study includes 14C dating of CO2, and determination of the greenhouse gas origins with isotope analyses such as d15N of N2O and d13C of CO2.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/875263

2022059971 Parsekian, Andy (University of Wyoming, Laramie, WY). Near-surface cryosphere geophysics as a nexus for interdisciplinary research between the Arctic hydrosphere, biosphere, and permafrost systems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS43A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The frozen regions of the earth--known as the cryosphere--are some of the most challenging locations to measure subsurface parameters, but these can also be critically important places to understand earth system processes due to their exposure to environmental change. A variety of cryosphere science questions are being addressed using near-surface geophysical measurements, and many are highly relevant to climate change. The consequences of a warming environment are reflected in altered hydrological processes, rapid geomorphological evolution, and resulting influences on biological patterns--parameters related to each of these disciplines may be acquired using near-surface geophysical measurements. Geophysical measurements from small to large scale are well suited to observe below-ground or ice-bound targets and contrasts between frozen and unfrozen materials. Geophysical measurements are actively used to retrieve parameters vital to understanding cryo-system function, often in 2D or 3D space or over time. In this talk, I will discuss recent results from cryosphere geophysics investigations at several scales, highlight exciting new research directions, and illustrate the strong connection between near-surface geophysics and cryosphere science with particular focus towards lakes and permafrost on the North Slope of Alaska. I will include examples related to spaceborne and ground-based geophysics and highlight radar, electromagnetic, and nuclear magnetic resonance methods. Finally, I will provide context about how the interdisciplinary cryosphere science community can be empowered through the enhanced availability of near-surface geophysical instrumentation.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/798829

2022055973 Pastick, Neal J. (U. S. Geological Survey, Earth Resources Observation and Science Center, Sioux Falls, SD); Zhu, Zhiliang; Genet, Helene; Koch, Joshua; Rey, David; Striegl, Robert G.; Wickland, Kimberly and Stephani, Eva. Quantifying hydrologic and cryologic conditions of dominant landscapes on the coastal plain of the Arctic National Wildlife Refuge [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1448, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Areas along the Arctic coast are changing the fastest among all of Earth's habitats due to climate change. In addition, there is growing interest in exploring for oil and gas resources in these areas which provide habitat for migratory birds, fish, caribou, and other species that are endangered or critical for local subsistence living. With ongoing permafrost thaw, future warming and interests in oil and gas extraction in the coastal plain (1002 area) of the Arctic National Wildlife Refuge, it is urgent to improve the understanding of this area and its vulnerability to change. To this end, we describe planned activities and showcase preliminary results from year 1 of a 3-year project aimed at developing detailed maps of the 1002 area, documenting soil temperature and moisture changes, measuring surface water flow and routes to rivers, lakes and ponds, and simulating surface and subsurface hydrology. This research leverages (1) field surveys to assess vegetation, topography, permafrost conditions and river discharge, (2) airborne and satellite imagery to document surface conditions and water flow through time and in unprecedented detail, and (3) advanced modeling to simulate historic (1950 - 2020) and future (2021 - 2100) land cover, permafrost, water flow, and nutrient and carbon dynamics assuming changes in climate and development. We will discuss designs of the study and describe initial results including the development of a high-resolution topographic map, time series of hydrologic and permafrost conditions, and field observations made in the summer of 2021. These data will help identify and model areas vulnerable to change and will allow managers to better understand risks and guide oil and gas development if it occurs.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/907605

2022059984 Paulus, Samantha (Virginia Polytechnic Institute and State University, Blacksburg, VA); Pearl, Brandon; Martin, Eileen Rose; Jensen, Anne M.; Ji, Xiaohang; Liew, Min; Nicolsky, Dmitry; Roth, Nolan; Zhu, Tieyuan and Xiao, Ming. Real-time data product streams for permafrost monitoring with distributed acoustic sensing [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract S15F-0314, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In August 2021, a fiber optic distributed acoustic sensing (DAS) array is deployed in Utqiagvik, Alaska to monitor the in-situ permafrost characteristics. Utqiagvik is an Arctic coastal community where infrastructure is threatened by permafrost degradation. The overarching goal of this project is to understand and forecast long-term variations of permafrost characteristics in Arctic Alaska using sensing technology, large-scale data transmission and analysis, and modeling. Changing ice content is related to seismic wave velocity, so we aim to use passive seismic monitoring to monitor shear wave and surface wave velocities in this multi-year study. DAS arrays utilize fiber-optic cable and a laser interrogator unit to measure seismic vibrations and record strain, strain rate, or velocity data. The DAS array measures spatially dense and high-frequency data, generating roughly one terabyte per week for this project. Due to a lack of high-performance computing resources and network connectivity in Utqiagvik, there is a need to calculate data products and compress data on-site as the data is continuously collected. We developed software modules for analysis prior to storage to fetch live data and generate streams of data products and compressed data. The DAS interrogator unit includes an application programming interface (API) for scientists to access data broken into short frames in memory. The API allows us to write python modules calculating custom data products during data acquisition. These data products are then small enough to enable remote data quality checks throughout the multi-year experiment. Further, when full hard drives are shipped to our universities for analysis, they allow for easier initial data exploration with lower input/output requirements than raw data. This initial exploration allows us to focus on the portions of raw data best suited to ambient seismic noise analysis.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/903553

2022059990 Pereira, Sebastian Ruiz (Pontifical Catholic University of Chile, Instituto de Geografía, Santiago, Chile) and Lambert, Fabrice. Water security and the hydric potential of Andean cryosphere [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract SY21B-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In dry regions, millions of people depend on freshwater provided by the mountain cryosphere. Its likely depletion would make productive land-use management and access to water supply an even more urgent priority. Therefore water-security-oriented policies increasingly rely on solid information feedbacks for projections provided by Earth Sciences. Nevertheless, this type of research still has a lot to understand regarding headwater catchment hydrology, the top global "water towers." For example, there are many theoretical and logistical uncertainties: "data deserts" in isolated areas, outdated legislation, or scarce research funding. Yet, one more important issue to highlight is the evolving nature of hydric resources, particularly where baselines have a large uncertainty and supply to many as in dry regions in the Andes or the Himalayas. The main concern here is the legislative inadequacy for evolving hydric resources as their baselines change. For example, groundwater within transboundary or paleowater aquifers could have unaccounted climate-sensitive recharge sources (e.g., permafrost thaw). Hence, the specific way of legislating mountain groundwater could turn ambiguous and useless. By reviewing particular legislation and landing the discussion on study cases in mountainous areas, we commit to showing the inadequacy of current legislation on hydric-potential evolution. Overall, water-security-oriented legislation will not assess and protect headwater catchments within the spectrum of different recharge processes throughout different hydroclimatic zones. First, the "evolving value" of specific catchments changes the nominal priority and purpose for protection. Secondly, a consistent failure to assess incommensurable (latent), climate-sensitive fractions of water supply structure is also found. Therefore, the policy recommendation is to use a hydric scale absorbing all nested processes necessary for hydric supply to persist, requiring defining a lifespan for legislation.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/811272

2022057099 Peters, Benjamin (Indiana University Bloomington, Department of Earth and Atmospheric Sciences, Bloomington, IN); Edmonds, Douglas A. and Broaddus, Connor. Does climate zone affect delta morphology? [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP55D-1134, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

River deltas are important landforms that support diverse ecosystems and provide fertile grounds for human habitation, and they are being threatened by rising sea levels due to climate change. The suitability of a given delta for occupation and how it might respond to sea-level rise depends, in part, on the number of distributary channels and their arrangement in space. Classically, this was thought to be determined by the balance between sediment delivered by rivers, and the redistribution of that sediment by tides and waves. Although delta morphology has been extensively studied, there have not been many attempts to distinguish between deltas in different climate zones. This lack of knowledge could hinder our efforts to fully understand the effects that a changing climatic environment could have on deltas. Toward this end, we explored how channel number on deltas varies as a function of climate zone. We used the global water occurrence data to count the number of channel mouths at the shoreline for 2,174 deltas across the world. Excluding the deltas with zero channels, delta channel number ranges from 1 to 162 with a mean value of 4.43 channels per delta. We found that the average number of channels increases from 3.84 in the tropical, lower latitudes to an average of 6.43 in the higher polar latitudes. Likewise, the average channel density (per square kilometer of delta) increased from 1.1 in the tropical latitudes to a maximum of 3.1 in the cold and polar latitudes. This suggests that deltas at higher latitudes are more densely channelized than those at lower latitudes, possibly due to the presence of river ice or permafrost. Using the Circum-Arctic Map of Permafrost and Ground-Ice Conditions we looked at whether channel number was a function of ground-Ice content and permafrost extent within the polar deltas themselves but found no conclusive relationship between these measures and channel number. If Arctic Deltas are morphologically distinct from their lower latitude counterparts, they may respond differently to rising sea levels, amplifying the need for future work to determine mechanistically why arctic deltas have more channels than deltas in other climate zones.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/993236

2022057022 Peterson, Sasha (University of Texas at El Paso, El Paso, TX); Lougheed, Vanessa; McClelland, James W. and Tweedie, Craig E. Spatial variability of permafrost soil organic carbon in the coastal bluffs of Elson Lagoon, Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C25F-0881, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost soil in northern Alaska contains a large amount of soil organic carbon (SOC), which through warming temperatures, and increasing coastal erosion, has become progressively more available to marine ecosystems. Thus, understanding any potential relationships between surface features and SOC is important for predicting land-ocean SOC transfer and marine ecosystem impacts. Utilizing remotely sensed data to assess coastal surface features is cost effective and scalable, however understanding what lays beneath the surface, and the relationship between surface features to SOC is not as well documented at high spatial resolution. An extensive soil sampling campaign was completed in July and August of 2019 on the coastline of Elson Lagoon near Utqiagvik. At twenty sites situated across primary polygonised tundra (PPT), a drained lake basin of old age (300-200 BP; DL-O), and a drained lake basin of medium age (50-300 BP; DL-M), a total of 96 cores were taken in the active layer, the upper organic-rich permafrost, and a deeper permafrost closer to sea level utilizing a horizontal coring method at the bluff face. Carbon content (%TC) was measured using a C:S LECO elemental gas analyzer: Preliminary results indicate that, %TC does not vary significantly between sites (ANOVA, p-values=0.115), or between geomorphic type (p-value=0.154). These results suggest that SOC varies independently of surface features and that it is not possible to extrapolate SOC from high spatial resolution maps of surface features derived from optical remote sensing methods. Furthermore, it was found that SOC decreased with depth, suggesting that studies that have extrapolated land-ocean SOC transfer from shallow SOC estimates may have overestimated inputs from coastal erosion.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/979078

2022057082 Piliouras, Anastasia (Los Alamos National Laboratory, Los Alamos, NM); Jones, Benjamin M.; Clevenger, Tabatha; Bull, Diana L.; Eymold, William Karl; Alexeev, Vladimir A.; Bennett, Alec P. and Rowland, Joel C. Fusing geospatial datasets to identify patterns and controls on Arctic coastal erosion [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP33A-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic coastal environments are rapidly changing in response to sea ice loss, permafrost degradation, and changing sea states. Intensification of Arctic coastal dynamics has been broadly noted, but variability in landscape morphology and local soil and/or permafrost conditions makes coastal erosion difficult to predict. Many of the environmental factors that influence erosion processes vary over a wide range of temporal and spatial scales. Further, in situ data collection in Arctic environments is limited. Remotely sensed observations and geospatial datasets allow us to examine the variability in coastal landscapes over large spatial extents to understand both the variability in surface and subsurface landscape conditions and how erosion rates vary with these conditions. Here, we present a compilation of remotely sensed and geospatial datasets on the North Slope of Alaska and use it to develop a set of coastal typologies that capture the variability in environments susceptible to coastal erosion. We describe the relationships between surface and subsurface characteristics and historical erosion rates, and we examine the sensitivity of erosion to numerous local conditions. Finally, we present a framework for using geospatial and remotely sensed data in combination with numerical modeling to estimate rates of shoreline change and sediment fluxes at the coarse scale of Earth system models.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/801008

2022059993 Pongracz, Alexandra (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Warlind, David; Miller, Paul A. and Parmentier, Frans-Jan W. Quantifying the impact of wintertime changes on the Arctic carbon cycle [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract U15A-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic is the fastest warming region of the world, which has a strong impact on the carbon cycle and vegetation dynamics. Even though the largest changes in temperature are projected to occur in the winter, cold season processes are often understudied and underrepresented in carbon cycle studies. This study aims to evaluate and quantify the impact of wintertime changes on the arctic carbon cycle by improving the representation of wintertime processes in the LPJ-GUESS DGVM. Firstly, we addressed shortcomings in the simulation of the insulation capacity of snow and its influence on soil temperatures. We implemented a new multi-layer snow scheme to account for the influence of snow dynamics on soil thermodynamics and biogeochemistry. The new scheme improved the model's ability to simulate soil temperature and permafrost dynamics. This resulted in significant changes to the modelled biogeochemistry such as increased winter respiration, changes in soil carbon content but also vegetation distribution. Looking forward, we will improve the physical controls on non-growing season greenhouse gas emissions in the model to enable a more realistic outgassing when soils freeze at the onset of winter. So far, our project demonstrates that wintertime changes significantly influence biogeochemical processes at high latitudes. By further refining modelled cold-season processes we aim to simulate snow-soil-vegetation interactions with improved certainty and provide more reliable future projections on the role of the cold season on the Arctic carbon cycle. Understanding these processes is essential to study the future of the arctic carbon cycle and associated climate feedbacks.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/836825

2022055971 Potter, Stefano (Woodwell Climate Research Center, Falmouth, MA); Natali, Susan; Burrell, Arden; Virkalla, Anna; Shestakova, Tatiana; Rogers, Brendan M. and Watts, Jennifer. Detecting hotspots of ecosystem change with remote sensing across the Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1444, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic is warming faster than any other region on Earth, at a rate nearly twice the global average, and this warming is expected to negatively impact vegetation, hydrology and terrain thaw. One of the most important global threats from the Arctic is permafrost degradation, which stores a vast amount of carbon that, if thawed, will amplify global warming through decomposition and release of carbon dioxide and methane into the atmosphere. Despite the potential consequences associated with these threats, there is a currently a limited understanding of these processes which makes it difficult to project or manage associated risks. Here we detect landscape changes in the Arctic using a suite of Visible, Near-Infrared and Thermal Infrared (VIS-NIR-TIR), and microwave remote sensing time series that provide ecological indicators for landscape freeze/thaw status, ecosystem water stress and vegetation state over a temporal period of up to 40 years in length. More specifically, we examine trends in the timing of the annual start of the growing season, annual growing season length, surface frozen status, surface soil moisture, surface water inundation, temperature, precipitation, snow melt, permafrost active layer depth, and vegetation health. We then combine these indicators to create maps which highlight "hotspots" of ecosystem change across different scenarios including greening/wetting, drying/browning, permafrost, temperature, precipitation and seasonal changes. Lastly, we use these relatively coarse hotspots maps together with higher resolution Landsat/Sentinel imagery to examine local drivers of change in regional case studies across a variety of Arctic ecosystems.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/940183

2022057035 Pradhan, Ipshita Priyadarsini (Indian Institute of Technology Mandi, School of Engineering, Mandi, India) and Shukla, Dericks P. Long- and short-term temporal analysis of satellite-derived permafrost terrains of Himachal Pradesh, India [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0935, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost region is highly vulnerable to climate change and is easily degraded by thermal and mechanical forces. Its extent and distribution in the Indian Himalaya region are not explored much and their mapping in Himalayan region is not carried out a lot. While around 9% of land area of Kullu district is categorized as permafrost areas. Given the socioeconomic consequences of permafrost degradation, detecting, mapping, and monitoring permafrost distribution in Himachal Pradesh are critical. This article provides a permafrost map for Himachal region based on continuous time-series analysis of Land Surface Temperature (LST) data using Google Earth Engine (GEE) platform. The LST from Landsat 8 (L8) and Moderate Resolution Imaging Spectroradiometer (MODIS) data were calculated using the GEE platform. Once whole scene falling at path 147 row 037,038,039 was taken for analysis covering 5500´3500 pixels at 30 m spatial resolution for L8. and path row covering 396´217 pixels at 1 km resolution for MODIS data. LST was prepared from 2013 to 2021 on each pass of the satellite. Thus nearly 495 data scenes were analyzed for L8 and 2913 data scenes for MODIS. The effect of presence of cloud shows sudden variations in derived LSTs which was overcome by removing clouds using cloud masking. The Indian Meteorological Department (IMD) observed temperature data during same time was compared with the derived LST values for few Himalayan stations. While under clear sky conditions, the mean LSTs are significantly correlated with the ground observation temperature data. The season wise variation of derived LST correlates more with the observed values. The Permafrost terrains were located and mapped in regions where the temperature is consistently lower than -1°C. Land degradation in such areas is being presented with the help of long term and short term temporal analysis.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/1002002

2022057050 Putkonen, Jaakko (University of North Dakota, Harold Hamm School of Geology and Geological Engineering, Grand Forks, ND); Shanks, Miranda and Mahmood, Taufique H. Detecting buried ice masses; Transantarctic Mountains, Antarctica [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C45D-1041, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Glacial ice can yield information on paleoclimate, paleo atmosphere, and ancient organisms. Throughout the Transantarctic Mountain Range (TAM), a minimal number of buried ice masses have been discovered which have the potential to be much older than most glaciers. An example of such is found in Ong Valley, Antarctica covered by a sublimation till that is >1.1 Ma years old, consequently making it one of the oldest known ice masses on Earth. In addition to a few known locations, no systematic effort has been made to map such ice masses in Antarctica. We visually analyzed >8,000 high resolution satellite images covering the TAM from Victoria Land to Pensacola Mountains. The multispectral imagery has sub-meter resolution (0.32-0.5 m) which allowed for permafrost polygon detection. The satellite imagery contains bands 1-3 (Red, Green, Blue) covering a spectrum from 400 to 745nm. On those images we inspected all land areas that were not covered by exposed ice and looked for land areas with polygonal patterned ground which is known to occur only when regolith either covers ice or the regolith is cemented by ice (ice cementation refers to the regolith that contains only interstitial ice, but no massive ice is necessarily present). Once we discovered the polygonal surface pattern the corresponding digital elevation model (REMA) was inspected. When a massive ice body is present in a U-shaped glacial valley it forms a convex shape on the bottom of the otherwise U-shaped valley cross profile. The REMA DEM was used to determine whether the given valley floor had a convex pattern that reveals the presence of buried ice body. Based on these analyses, we identified 28 individual field sites that all fill both the above-mentioned criteria, and thus have a strong likelihood of containing a massive buried ice body.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/909470

2022055975 Qu, Bo (Université de Montréal, Département de Géographie, Montreal, QC, Canada); Roy, Alexandre; Melton, Joe; Black, Thomas A.; Amiro, Brian D.; Margolis, Hank; Euskirchen, Eugenie Susanne; Ueyama, Masahito; Kobayashi, Hideki and Sonnentag, Oliver. Site-level evaluation of boreal forests' carbon dioxide and energy fluxes along a permafrost gradient in CLASSIC [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1451, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Rapidly changing boreal forest composition, structure and functioning may strongly influence carbon cycle processes and climate system. Predicting the carbon dioxide (CO2) and energy fluxes by models is critical to evaluate boreal forest's role in the global climate system. However, uncertainties remain, largely due to landscape heterogeneity challenging the adequate representation of boreal forests in ecosystem models and the land component of climate models. Eddy covariance (EC) and supporting environmental observations made across boreal forest stands characterized by different stand characteristics and permafrost conditions provide valuable data sets to benchmark models against. Here, we compiled EC and supporting data from eight boreal forest stands distributed across North America to evaluate the CO2 and energy fluxes represented by Canadian Land Surface Scheme including Biogeochemical Cycles (CLASSIC). Collectively, the stands are characterized by increasing permafrost extent (from permafrost-free to continuous permafrost) and decreasing tree crown coverage (from 100% to 15%) with increasing latitudes. Based on a comprehensive set of in-situ vegetation survey measurements, the dominant overstory and understory plant functional types were adequately represented in the latest version of CLASSIC. We investigated model performance by multiple skill metrics and analysed the influence of environmental variables on the model accuracy. Overall model performance varied among sites and seasons. For example, the root mean square error of modelled net ecosystem production and latent heat (LE) tended to be lower at high-latitude stands. Modelled gross primary productivity (GPP), ecosystem respiration and LE were slightly overestimated by correlating well with observations. On a monthly basis, we found that summer (June to August) presented higher correlation than other seasons and in contrast, was the main sources of annual bias. Analysing the links between model bias and environmental variables provides suggestions to guide model improvements. For example, preliminary results demonstrate the inadequate representation of photosynthetic CO2 uptake to air temperature, high-level vapor pressure deficit, and high-level shortwave radiation explained the main model bias in GPP and NEP.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/922713

2022059980 Raberg, Jonathan (University of Iceland, Department of Earth Sciences, Reykjavik, Iceland); Miller, Gifford H.; Geirsdottir, Aslaug and Sepulveda, Julio. Widespread trends in brGDGT distributions span over a dozen sample types [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract PP25D-0959, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Branched glycerol dialkyl glycerol tetraether (brGDGT) lipid biomarkers are a valuable tool in the study of Earth's paleoclimate. Empirical relationships between brGDGT distributions and environmental parameters, especially temperature and pH, make them useful proxies in a variety of sedimentary archives. Part of their utility comes from the fact that they are widespread in nature. BrGDGTs have been measured in over a dozen sample types across the globe, from Arctic permafrost and alpine lakes to hot springs and deep ocean trenches. The relationships between brGDGT distributions and environmental parameters in these diverse sample media are often similar (e.g., higher methylation number usually corresponds to colder temperature), but are generally different enough to prevent the merger of datasets containing different sample types. This separation has led to independent proxy calibrations for different sample types and necessitated much effort to determine the origin(s) of brGDGTs in sedimentary archives. Recently, we found that grouping brGDGTs based on their structural characteristics clarified relationships between brGDGTs and some environmental parameters in lake sediments. Here, we extend this technique to a compiled dataset of >2500 published samples spanning over a dozen sample types. We find multiple relationships between brGDGTs, temperature, and pH that are nearly universal across these diverse environments and discuss the potential implications of these observed trends.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/906396

2022057055 Rehder, Zoé (Max Planck Institute for Meteorology, Department of the Land in the Earth System, Hamburg, Germany); Kleinen, Thomas; Kutzbach, Lars; Stepanenko, Victor and Brovkin, Victor. New process-based model for methane emissions from ponds (MeEP) reveals length of ice-free season has strong impact on increased emissions under warming [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-05, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost ponds are a steady source of methane. However, it is difficult to gauge the sensitivity of pond methane emissions to climate-change induced warming, because pond methane emissions show large spatiotemporal variability already on local scale. We study this sensitivity on landscape level with a new process-based model for Methane Emissions from Ponds (MeEP model). The model was set up for the polygonal tundra in the Lena River Delta. Due to a temporal resolution of one hour, it can capture both diel and seasonal variability in methane fluxes. MeEP also reproduces one of the main drivers of spatial variability, the ground heterogeneity. Depending on where ponds in the polygonal tundra form, they can be classified as ice-wedge, polygonal-center, or merged-polygonal ponds. In MeEP, each of these pond types is simulated separately and the representation of these ponds was informed by dedicated measurements. In addition to a process-based representation of the methane fluxes, MeEP simulates the temperature profile of both the ponds and the surrounding soils. The modelled methane fluxes are validated against Eddy-covariance measurements, where we see a good fit. When comparing the emissions from ponds under different baseline temperatures, we find that an increase in the length of the ice-free season leads to a similar in the total ice-free season emissions as the increase of mean emissions due to increased temperatures, thus roughly doubling the emission increase under warmer conditions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/828569

2022057057 Rettelbach, Tabea (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Potsdam, Permafrost Research Section, Potsdam, Germany); Langer, Moritz; Nitze, Ingmar; Jones, Benjamin M.; Helm, Veit; Freytag, Johann-Christoph and Grosse, Guido. Evaluating the effects of tundra fires on soil microtopography and hydrologic surface networks in polygonal permafrost landscapes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

With the Earth's climate rapidly warming, the Arctic represents one of the most vulnerable regions to environmental change. These northern high latitude regions experience intensified fire seasons and especially tundra fires are projected to become more frequent and severe. Fires in permafrost regions have extensive impacts, including the initiation of thermokarst (rapid thaw of ice-rich ground), as they combust the upper organic soil layers which provide insulation to the permafrost below. Rapid permafrost thaw is, thus, often observable in fire scars in the first years post-disturbance. In polygonal ice-wedge landscapes, this becomes most prevalent through melting ice wedges and degrading troughs. The further these ice wedges degrade, the more troughs will likely connect and build an extensive hydrological network with changing patterns and degrees of connectivity that influences hydrology and runoff. While subsiding troughs over melting ice wedges may host new ponds, an increasing connectivity may also subsequently lead to more drainage of ponds, which in turn can limit further thaw and help stabilize the landscape. To quantify the changes in such dynamic landscapes over large regions, highly automated methods are needed that allow extracting information on the geomorphic state and changes over time of ice-wedge trough networks from remote sensing data.We developed a computer vision algorithm to automatically derive ice-wedge polygonal networks and the current microtopography of the degrading troughs from very high resolution, airborne laser scanning-based digital terrain models. We represent the networks as graphs (a concept from the computer sciences to describe complex networks) and apply methods from graph theory to describe and quantify hydrological network characteristics of the changing landscape. In fire scars, we especially observe rapidly growing networks and fast micromorphological change in those degrading troughs. In our study, we provide a space-for-time substitution comparing fire scars throughout the Alaskan tundra of up to 70 years since the fire disturbance, to show how this type of disturbed landscape evolves over time.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/931572

2022055945 Rinnan, Riikka (University of Copenhagen, Center for Permafrost, Copenhagen, Denmark); Kramshoj, Magnus; Davie-Martin, Cleo; Elberling, Bo and Albers, Christian N. Exchange of biogenic volatile organic compounds in soil; source or sink? [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A22E-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Concentrations of biogenic volatile organic compounds (BVOCs) in soil, as well as their fluxes between soil and the atmosphere, vary substantially, both temporally and spatially. This is likely due to the fact that two opposing processes, BVOC production and consumption, occur simultaneously. Using Arctic permafrost soil samples as model soils, we conducted laboratory experiments to assess net BVOC release rates upon permafrost thaw. BVOC concentrations were measured using proton-transfer-reaction mass spectrometry and some experiments were coupled with mineralization assays to study BVOC consumption. In general, permafrost soils initially released substantially higher BVOC quantities than corresponding arctic active layer soils, but the release rates declined soon after. The decrease in the net release rate after the initial peak was likely because the released compounds originated from gases trapped in the frozen permafrost, rather than active microbial production, as well as due to an increase in microbial BVOC consumption rates. Results from our mineralization assays using 14C-labelled BVOCs suggest that soil BVOC uptake is largely due to microbial mineralization of the compounds to CO2. Microbial BVOC consumption seems to be common to all soils and is a process likely controlling the net BVOC release rates from soil, similar to how methane oxidation controls net methane emissions. This presentation will also discuss whether soil microbial BVOC consumption could act as a sink for BVOCs produced by plant canopies.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/886305

2022057054 Rodenhizer, Heidi (Northern Arizona University, Center for Ecosystem Science and Society, Flagstaff, AZ); Belshe, Fay; Celis, Gerardo; Ledman, Justin; Mauritz, Marguerite; Goetz, Scott J.; Mack, Michelle C.; Sankey, Temuulen and Schuur, Edward. Carbon release accelerated by abrupt thaw at Eight Mile Lake, AK [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Abrupt thaw of permafrost has the potential to approximately double carbon emissions from permafrost through gradual thaw by 2300, but in field studies, the impact of abrupt thaw on carbon fluxes varies widely, and we have yet to inventory thermokarst features across the circumpolar region. In this study, we developed the thermokarst detection algorithm, a method of detecting thermokarst features using a single elevation data set, applied it to an 81 km2 area surrounding Eight Mile Lake, AK, just north of Denali National Park, and evaluated the impact of abrupt thaw on carbon dioxide and methane fluxes using eddy covariance. We found that 7% of the site is thawing abruptly, with largest number of features being small thermokarst pits, but the largest impact by area occurring from water tracks. Previous research using eddy covariance has shown that this site is a consistent source of both carbon dioxide and methane to the atmosphere. During the growing season, abrupt thaw promoted higher carbon dioxide uptake, but this was more than offset by higher release during the non-growing season, resulting in increased release of carbon dioxide annually. This pattern was likely due to the importance of water tracks at the site, as plant growth is higher in water tracks but deeper thaw and later freeze-up offset this by stimulating heterotrophic respiration. Sites with different thermokarst morphologies could see very different responses, as plant growth is not stimulated in all thermokarst features. Additionally, methane production was promoted by abrupt thaw nearly year-round, causing significant additional radiative forcing, despite the much smaller magnitude of methane fluxes. Overall, our findings support the high release of carbon from permafrost soils through abrupt thaw and highlight the need to map thermokarst features across the circumpolar region to allow benchmarking as abrupt thaw is incorporated into Earth System Models.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/799825

2022055977 Rogers, Brendan M. (Woodwell Climate Research Center, Falmouth, MA); Natali, Susan; Watts, Jennifer; Virkalla, Anna; Christensen, Torben R.; Euskirchen, Eugenie Susanne; Fiske, Greg; Gandois, Laure; Goeckede, Mathias; Humphreys, Elyn; Lohila, Annalea; Pallandt, Martijn; Mauritz, Marguerite; Prokushkin, Anatoly Stanislavovich; Schuur, Edward; Sonnentag, Oliver; Varlagin, Andrej; Windholz, Tiffany and Zona, Donatella. Developing a ground observation network to monitor carbon fluxes across the Arctic-boreal zone [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B22D-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic-boreal zone has historically been a carbon sink, resulting in large carbon stores in soil organic matter and permafrost. Climate change and associated warming, however, may be transitioning this region into a carbon source, or will do so in the near-future. Greenhouse gas emissions from decomposing soil organic matter, disturbances, and permafrost thaw across the Arctic-boreal zone could hinder society's ability to meet global temperature goals set by the Paris Climate Agreement. Despite the importance, the scientific community's ability to monitor carbon fluxes from this critical region, and to understand and map the ecosystem, soil, and climate drivers, remains limited. This is largely due to challenges associated with conducting ecosystem-scale measurements in remote environments and throughout the non-growing season using the eddy covariance technique, as well as barriers to data processing and sharing. Here we describe the distribution of current ground-based carbon flux sites as well as new eddy covariance sites under development. With participation and guidance from northern communities, the Arctic-boreal flux science community, and existing measurement networks, we aim to install several new eddy covariance towers and further instrument existing sites to measure CO2 and CH4 fluxes across much of the year. We present our process for site selection, plans for upcoming years, and describe opportunities for international collaboration and support for flux site establishment, instrumentation, maintenance, and data collection and coordination. We also illustrate how this expanding ground network can integrate with related research on monitoring, mapping, and projecting carbon fluxes across the Arctic-boreal zone.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/893709

2022057020 Rolph, Rebecca (Humboldt University of Berlin, Department of Geography, Berlin, Germany); Lantuit, Hugues; Overduin, Paul and Langer, Moritz. Numerical modelling of pan-Arctic erosion using globally-available forcing data [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C25F-0876, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

As air temperatures rise and sea ice cover declines in the Arctic, permafrost coastal cliffs thaw more rapidly and wave energy rises. Thus, as the open water season continues to lengthen, climate change triggers a large part of the Arctic shoreline to become increasingly vulnerable to erosion. Arctic erosion supplies nutrient-laden and carbon-rich sediment into nearshore ecosystems. A retreating coastline also has consequences for residential, cultural, and industrial infrastructure. Despite its importance, erosion is currently neglected in global climate models, and existing physics-based numerical models of Arctic shoreline erosion are too complex and regionally-focused to be applied on a pan-Arctic scale. Here, we apply our simplified numerical erosion model, ArcticBeach v1.0, to the entire Arctic coastline. ArcticBeach v1.0 has previously been shown to simulate retreat rates at two sites that differ substantially in their main mechanisms of retreat (sub-aerial erosion/thaw slumping versus notch/block erosion). The model uses heat and sediment volume balances in order to predict horizontal cliff retreat and vertical erosion of a fronting beach. It contains an erosion module that uses empirical equations to estimate cross-shore sediment transport, coupled to a storm surge module forced by wind. We compare our results with the existing observations and statistically-derived projections of retreat, as well as provide an analysis of seasonal trends in the ERA5 climate forcing data used. We present Arctic maps of regional variation in trends in 2-meter air temperature, sea ice concentration, and wind speed.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/886742

2022057044 Rosado, Albin (Virginia Polytechnic Institute and State University, Department of Civil and Environmental Engineering, Blacksburg, VA); Stark, Nina; Eidam, Emily; Franke, Kevin; Markert, Kaleb and Hall, Josephine. Towards understanding the relationship between coastal and riverine processes and civil infrastructure in the Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C44A-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Coastal and riverine Arctic communities are impacted by natural processes such as erosion, flooding, and permafrost thaw. In many communities, the impacts of these processes are intensifying with climate change. Civil infrastructure in Arctic communities can be significantly impacted by these processes. The built environment plays an important role in the wellbeing of these communities as it facilitates essential services to the communities. However, knowledge gaps still exist regarding the understanding of the relationship between the built environment and coastal and riverine processes. Here, we present the synthesis of a detailed literature review on currently available data and observations on the interaction between coastal and riverine processes and the built environment in Arctic communities and provide an outlook towards future trends in the context of climate change. Initial observations suggest that erosion, flooding, and permafrost thaw damage infrastructure in over 40% of all communities in Alaska. Furthermore, we discuss existing knowledge gaps and pathways to fill these gaps through innovative and sustainable data collection strategies.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/995840

2022059992 Ruane, Alexander C. (NASA, Goddard Institute for Space Studies, New York, NY); Ranasinghe, Roshanka; Vautard, Robert; Arnell, Nigel; Coppola, Erika; Cruz, Faye Abigail T.; Dessai, Suraje; Islam, Akm Saiful; Rahimi, Mohammad Murtaza; Ruiz-Carrascal, Daniel; Sillmann, Jana; Sylla, Mouhamadou Bamba; Wang Wen; Tebaldi, Claudia; Zaaboul, Rashyd; Iles, Carley and Servonnat, Jerome. IPCC AR6 WGI Chapter 12; Climate change information for regional impact and for risk assessment [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract U13B-12, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

This presentation will convey the assessments of the Intergovernmental Panel on Climate Change Sixth Assessment Report (IPCC AR6) Working Group I Chapter 12 as described by its author team. This chapter establishes the Climatic Impact-Driver (CID) framework to focus on sector-relevant climate information that is useful for adaptation and risk management planning while recognizing that the same climate change can have substantially different implications for different systems. It begins by defining 33 CIDs across heat and cold, wet and dry, snow and ice, wind, coastal and oceanic types (examples include heat extremes, hydrological drought, permafrost, tropical cyclones, and coastal flooding). Each CID is connected to key responses across the WGII sectors of land ecosystems, marine ecosystems, water resources, food, cities, health, and livelihoods, highlighting useful indices and thresholds for adaptation and risk-focused information. CID changes are then assessed across 59 land and ocean regions, allowing for examinations of unique and overlapping climate challenges for every part of the planet. CID changes are examined for their linear (or non-linear) relationships with global warming levels, revealing how patterns of CID change reach more extreme characteristics under scenarios where greenhouse gas emissions continue to rise. Each CID is also examined for characteristics that transcend regions, identifying unique challenges for biodiversity hot spots, cities, deserts, mountains, and tropical forests. The chapter then examines the time horizons for which each CID will emerge from its range of historical variability, allowing for even more clear recognition of human influence for each type of climate change. Finally, Chapter 12 includes a synthesis of the developing role of climate services in identifying climate information needs in support of adaptation and risk planning.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/796132

2022055998 Runge, Alexandra (Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research, Potsdam, Germany); Nitze, Ingmar and Grosse, Guido. Annual dynamics of retrogressive thaw slumps across NE Siberia with LandTrendr [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31E-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost temperatures increase globally and lead to extensive permafrost thaw. With increasing air temperatures, changing precipitation regimes, increased intensity and frequency of extreme events, and disturbances such as wildfires, permafrost is increasingly vulnerable to thawing. Permafrost thaw either occurs gradually over decades or is initiated through rapid and abrupt permafrost disturbance processes, which can develop within a few days to years. The impact of such rapid disturbances on Arctic-Boreal ecosystems can be drastic on local to regional-scale and a global impact has been suggested through soil carbon mobilisation. Retrogressive thaw slumps (RTS) are highly dynamic and abrupt permafrost disturbance features that result from slope failure from thawing of ice-rich permafrost. Although RTS are small-scale features, they often occur in clusters, significantly impacting the surrounding landscapes and ecosystems at high temporal scales. The occurrence and thawing activity of RTS signifies an increased permafrost vulnerability. So far, previous assessments focused on mapping RTS with remote sensing imagery at local-scale and deriving temporal information from few snapshots in time. A continuous and high temporal assessment of the disturbance dynamics at a representative larger-scale is still missing. Thus, our main objective was to map and monitor RTS on a continental-scale and assess their annual temporal thaw dynamics in Northeast Siberia. We adapted and parametrised LandTrendr, an automated temporal segmentation algorithm, to identify the abrupt annual RTS disturbances in Landsat and Sentinel-2 time series data. Additionally, we applied spectral and spatial masks and a machine learning classification for improved RTS mapping. Our results show the first continental-scale mapped RTS distribution in NE Siberia and their annual thaw dynamics from. Overall, the RTS thaw dynamics steadily increased in NE Siberia during the assessment period. At the same time, local assessments revealed distinct periods of increased and decreased thawing dynamics. This indicates spatiotemporal variability in thaw dynamics and a strong connection to local drivers. Overall, our results highlight increased permafrost thaw, its large-scale impact and heightened permafrost vulnerability to thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/880234

2022057065 Sakhalkar, Soumitra (University of Alaska Fairbanks, Fairbanks, AK); Meyer, Franz Josef and Zwieback, Simon. InSAR-based analysis of seasonal permafrost deformation in the Yukon Wildlife Refuge [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Permafrost in Alaska has been warming and thawing at an increasing rate and while many ground-based measurements have been carried out, these lack the spatial coverage needed for regional monitoring. Moreover, with the increase in air temperatures, more wildfires have been reported in ecologically sensitive areas such as the Yukon Wildlife Refuge located in the Yukon Flats. Wildfires are known to stimulate permafrost thaw: in areas with ice rich permafrost, wildfires can trigger subsidence. Impacting the hydrologic functioning, habitat and water resources. However, the subsidence rates remain poorly constrained on regional scales.In this study, we use Sentinel-1 InSAR to assess the seasonal surface deformation of two previously burned fire-scars in the Yukon Wildlife Refuge, between 2017 and 2020. The Discovery Creek fire took place in 2013, and the Mt. Schwatka fire in 2015. By combining ascending and descending observation geometries, a first-order estimate of vertical displacement was derived using the SBAS algorithm. We find that the unburned areas tend to have lower seasonal deformation on average, compared to the burned areas. The impact of fire on the seasonal deformation is also higher on the more recent Mt. Schwatka fire than the Discovery creek fire. The inter-annual variability highlights the sensitivity of the permafrost ecosystems to meteorological conditions across a range of time scales. Future work will aim to assess the impact of repeat burning, to better understand the relation of wildfires on permafrost stability.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/999683

2022057008 Sanders, Jillian (Texas A&M University, College Station, TX); Loisel, Julie and Smith, A. Peyton. Investigating the impacts of climate warming on mineral and organic permafrost soil carbon [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B54E-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic region is warming two times faster than the global average rate, with some areas warming faster than others. This warming will cause changes to ecosystem structure as temperature and precipitation increase throughout the 21st century. It is estimated that the Arctic contains half of the global soil carbon pool, and climate warming will lead to considerable degradation of permafrost. This degradation may lead to the expansion or drainage of Arctic peatlands, which would alter the global carbon budget. The purpose of this research study is to better understand the sensitivity of different Arctic soil types to warmer growing seasons. In this study, we measured carbon dioxide (CO2) emissions from two soil types (lowland peatland and upland (mineral) tundra) using 16 intact, replicate soil cores (8 of each type) that were incubated aerobically at 1°C and 6.5°C for 100 days. Soil moisture content was maintained near field conditions throughout the incubation process. An additional component of the study measured CO2 emissions from individual, partitioned soil layers (live biomass vs. organic litter vs. mineral layer) from the same sites as the whole cores. These individual layers were incubated under the same conditions as the whole cores to better understand the sensitivities of different soil types to permafrost thaw and climate warming. For both the intact cores and the partitioned layers, static sampling was conducted 3 times the first week, then 2 times per week for 4 weeks, and 1 time per week for the remainder of the experiment. The incubations were completed in summer 2021 and statistical analysis is underway. Overall, this study is expected to provide benchmarks for Arctic soil decomposition models, help predict future carbon budgets, and provide information for climate mitigation efforts.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/870124

2022055955 Scheel, Maria (Aarhus University, Department of Bioscience, Aarhus, Denmark); Zervas, Athanasios; Jacobsen, Carsten Suhr and Christensen, Torben R. Microbial comparative transcriptomics in abruptly thawing Greenlandic permafrost [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B11B-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic permafrost is estimated to store 1850 Gt carbon (C), corresponding to about twice the amount of current atmospheric CO2. After being frozen for a minimum two but often thousands of years, microorganisms inhabiting these soils face new environmental conditions upon thawing. Gaps of knowledge exist in their metabolic response to increasing lability of ancient C stocks under warmer temperature regimes and liquid water availability. Microbial conversion of these C stocks potentially acts as sink or source of greenhouse gases, such as CO2 and CH4 and could further impact C fluxes to the atmosphere. These carbon decomposition processes have implications for predictions in global models. Hence, knowledge about microbial carbon sequestration in thawing soils is crucial - yet understudied, particularly in remote environments. Environmental total RNA reflects all genes expressed by the soil microbiome in response to physicochemical conditions, such as abrupt thaw and erosion. Taxonomic composition, community changes, possible survival mechanisms as well as metabolic pathways of microbial organic carbon remineralization, methanogenesis and/or -trophy of soil microorganisms will be revealed. Here, we sampled the seasonally thawing active layer, freshly thawed transition zone and intact permafrost layer of a 2-year-old abruptly collapsed thermal erosion gully in the remote high Arctic, Zackenberg, Northeast Greenland. From a 1 m deep and up to 26200-year-old soil core, total RNA was extracted and sequenced with Illumina NextSeq. Gene expression of samples describes the community composition (rRNA) and organism-level active metabolic pathways (mRNA) in zones of intensely degrading permafrost. The impact of changing physicochemical soil parameters with depth, such as pH, age, soil moisture and organic matter content was compared to determine possible metabolic and community-level responses. Implementation of bio-indicator signatures in thawing permafrost soils for monitoring was investigated.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/806992

2022057098 Schmeer, Maria (Washington University, St. Louis, MO); Douglas, Madison; Miller, Kimberly Litwin and Lamb, Michael P. Using temperature sensors to track the thaw and erosion fronts in an experimental permafrost riverbank [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP55C-1130, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

As Arctic rivers warm, more heat is available to thaw permafrost, which can destabilize riverbanks and affect Arctic riverside communities. The thermal characteristics and geomorphic processes active in Arctic rivers change seasonally and inter-annually, making it difficult to isolate bank thaw and erosion patterns from field measurements alone. In particular, little is known about how the thaw interface within a riverbank migrates during warming and erosion. To investigate this process, we designed a frozen flume experiment with two phases to track the thaw and erosion fronts within a permafrost bank. In the first phase, discharge increased as the bank widened to keep velocity and boundary stresses constant. The sediment transport capacity was high during phase one such that eroded sediment was flushed downstream. In the second phase, the discharge was fixed as the channel widened, which created a backwater effect that resulted in lower boundary stresses and a layer of thawed sediment that draped the frozen bank. We used an array of temperature sensors in the bank to determine the thaw and erosion front locations throughout the experiment to assess whether bank erosion was thaw- or sediment transport- limited. Preliminary results show how temperature sensors can be used to track thaw and erosion fronts at bank locations, demonstrating their potential for use in field studies to assess riverbank erosion hazards for Arctic communities.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/952823

2022057021 Schmidt, Juditha (University of Oslo, Department of Geosciences, Oslo, Norway); Etzelmuller, Bernd; Schuler, Thomas; Magnin, Florence; Boike, Julia; Langer, Moritz and Westermann, Sebastian. Surface temperatures of coastal rock walls in the High Arctic (Kongsfjorden, Svalbard) [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C25F-0878, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic coastlines and corresponding erosion rates as well as natural hazards have been in the focus of research in recent years. While most studies discuss coastal dynamics in ice-rich permafrost, coastal high-Arctic rock walls and their thermal regime are still poorly understood. In this study, we present four years of rock surface temperature (RST) measurements of rock walls in Kongsfjorden, Svalbard, including a comparison between coastal and non-coastal settings. Furthermore, we give insights into one year of RST measurements along the coastline ranging from the inner to the outer part of Kongsfjorden as well as coastal rock walls at the open sea. For evaluation, we applied the surface energy balance model CryoGrid 3, taking into account modified radiative forcing in vertical rock walls. Our measurements show that coastal cliffs are characterized by higher RST than non-coastal rock walls with up to 1.5°C difference in mean monthly values. The model evaluations indicate that this effect results mainly from (1) higher air temperatures at the coast compared to inland settings and (2) long-wave emission by relatively warm seawater. Ice coverage on the fjord counteracts this effect. Consequently, sea ice loss might lead to higher RST in coastal rock walls during previous periods of sea ice coverage. Calculations of the surface energy balance show that fluxes in coastal and non-coastal settings differ only slightly in summer and fall. However, pronounced differences can be detected in winter and spring, when the water body of the fjord acts as an additional energy source for the coastal settings.We discuss different factors for the thermal regime of high-Arctic rock walls, as well as implications for the erosion of these coastlines in a future warmer climate.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/930955

2022055995 Schuur, Edward (Northern Arizona University, Center for Ecosystem Science and Society, Flagstaff, AZ). The vulnerability of permafrost carbon to climate change; key findings from a decade of synthesis [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31E-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Factors that control terrestrial carbon storage in arctic and boreal ecosystems are changing. Surface air temperature has risen 2.5 times faster in the Arctic compared to the whole Earth, and permafrost temperatures have been increasing over the last 40 years. Disturbance by fire (particularly fire frequency and extreme fire years) is higher now than in the middle of the last century. Soils in the northern circumpolar permafrost zone store 1,460 to 1,600 petagrams of organic carbon (Pg C), almost twice the amount contained in the atmosphere and about an order of magnitude more carbon than contained in plant biomass (55 Pg C), woody debris (16 Pg C), and litter (29 Pg C) in the boreal forest and tundra biome combined. This large permafrost region soil carbon pool has accumulated over hundreds to thousands of years, and there are additional reservoirs in subsea permafrost and regions of deep sediments that are not added to this estimate because of data scarcity. Following the current trajectory of global and Arctic warming, 5% to 15% of the organic soil carbon stored in the northern circumpolar permafrost zone is considered vulnerable to release to the atmosphere by the year 2100. In addition to changing soil organic carbon pools, there is heightened recognition that release rates from inorganic carbon reservoirs in the form of methane hydrates and geologic methane seeps may be increasing due to the opening of new pathways to the atmosphere through degrading permafrost. Many of the abrupt processes that thaw permafrost and release carbon are not represented by Earth System Models but have been described by reduced complexity models. These simplified models project up to 50% additional carbon release by abrupt thaw mechanisms, but often do not include the response of vegetation that can offset carbon release. An Earth System Model intercomparison project suggested that additional plant carbon uptake, growth, and deposition of new carbon into soil would together completely offset any soil carbon loss this century, and that it would take several centuries before cumulative losses from soils would overwhelm new carbon uptake. Despite these differences, the intercomparison and other studies have indicated that future scenarios with limited human greenhouse gas emissions would reduce changes to high latitude ecosystems.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/913080

2022056012 Sergeant, Flore (Laval University, Quebec City, QC, Canada). Testing the linear relationship between recession dynamics and active layer thickening over 336 catchments located in permafrost regions [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1748, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Due to climate warming, permafrost from Arctic zones thaws and the thickness of its overlying active layer increases. This impacts the subsurface hydrologic regime of the draining watershed: baseflow to surface water and recession characteristics are modified. The active layer thickening is generally assumed to be linearly correlated with the subsurface flow modification. The objective of this study is to test this assumption by quantifying the correlation between the temporal evolution of hydrologic parameters and surface, subsurface and climatic controlling factors. This test is performed for 336 Arctic catchments and over the 30-year time period 1970-2000. Unlike previous studies, we demonstrate a clear decrease in recession slope and initial recession outflow over the 30-year time period for a majority of catchments at any significance level. We explain this result by identifying controlling factors (topography, permafrost ice content) that complexify the relationship between trends in recession parameters and active layer thickness evolution. The novel aspect of the study lay behind the large number of studied catchments and the large range of controlling factors tested. Keywords: arctic hydrology, large-scale, recession analysis, thawing permafrost, active layer thickening.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/840775

2022055968 Shelef, Eitan (University of Pittsburgh, Pittsburgh, PA); Abbott, Mark B.; Griffore, Melissa; Wondolowski, Nicholas Aksel and Mark, Sam. Sensitivity of erosion-rate in permafrost landscapes to environmental conditions based on a sedimentary record from Burial Lake, AK [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1439, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Erosion of permafrost landscapes can affect the resiliency of the Arctic ecosystem by transforming sediment and nutrient fluxes, surface and subsurface hydrology, soil properties, and rates of permafrost thaw. Despite the importance of these erosional processes, they remain difficult to quantify and model. This difficulty primarily stems from the complexity of the Arctic system, where interactions between climate, permafrost, hydrology, soil properties and vegetation can influence erosion-rates in unexpected ways. To constrain this complex system, we utilize a data-rich sediment record from Burial Lake, Alaska, that enables us to explore the conditions associated with changes in erosion-rates over the past 25 kyr. Our analysis, based on multivariate techniques, shows that erosion-rate is strongly associated with a set of sedimentary parameters, including isotopic and elemental ratios, pollen, and sedimentary proxies for temperature and precipitation. Some of these parameters covary, and the relations between them and erosion-rate are often non-linear and sometimes counterintuitive. For example, erosion-rate in this arctic system generally decreases with increased precipitation and temperature, in contrast with some geomorphologic preconceptions. Results suggest that increased temperature and precipitation are associated with increased vegetation cover that protects the landscape from erosion. Pollen records reveal vegetation species that are most likely to influence erosion-rate. Our findings also hint that the values of some sedimentary parameters covary with erosion rate because they reflect the depth of incision into a soil profile. Analysis of lake sediments from additional locations will help explore the spatial variability in these patterns.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/919541

2022057016 Shiklomanov, Nikolay I. (George Washington University, Washington, DC); Klene, Anna E.; Nyland, Kelsey E.; Streletskiy, Dmitry A. and Nelson, Frederick E. Analysis of permafrost-vegetation interactions based on long-term ground surface observations [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C22C-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The relationship between the permafrost system and the warming climate is not direct; the climatic signal is altered by the insulating effect of natural ground covers such as snow and vegetation. As a result, the magnitude and timing of the signal even at shallow depths may not closely correspond to those of the initial climatic forcing. Numerous studies have suggested that widespread changes in Arctic vegetation are happening across Arctic ecosystems in response to climate change. Such vegetation changes are associated with contrasting feedbacks and non-linear effects on the ground thermal regime, the active layer, and permafrost that evolve over multi-decadal scales. We present long-term (1995-2019) observations of the active layer and ground surface temperatures from the Alaskan network of Circumpolar Active Layer Monitoring (CALM) sites. These sites are representative of major land-cover classes along the dominant bioclimatic gradient. To evaluate the effect of vegetation changes on the ground thermal regime the analysis is focused on the warm (thawing) season. Several simple indices that indirectly account for complex energy-exchange processes between the atmosphere and the ground surface are used to quantify the effects of generalized vegetation types on the ground thermal regime and to assess the multi-decadal changes in thermal insulation properties of vegetation. Our data indicate that for shrub-free tundra, vegetation change produces a negative feedback by increasing the summer thermal insulation of ground cover, which can partially explain the relative stability of active-layer thickness under a warming climate. Conversely, in landscapes dominated by shrubs, similar climatic forcing resulted in a positive (deepening) active-layer trend. The observational data presented here provide an empirical basis for the quantitative evaluation of complex interactions between changing ecosystems and permafrost.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/924328

2022059966 Shoemaker, Emileigh (University of Arizona, Tucson, AZ); Baker, David M. H.; Richardson, Jacob A.; Scheidt, Stephen P.; Whelley, Patrick; Carter, Lynn M. and Young, Kelsey. A multi-frequency ground penetrating radar investigation of buried ice beneath pyroclastic deposits at Askja Volcano, northern Iceland [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS13A-06, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

From 2010-2016, it was estimated that ~7% of the land area of Iceland was underlain by permafrost. This permafrost maintains a tenuous stability at higher altitude mountainous regions like Askja Volcano located in the Northern Icelandic highlands. Eruptions in 1875 and 1961 deposited rhyolitic pumice and basaltic lapilli, respectively, which preserved a layer of seasonal snowpack in each case that later densified into massive ice. This ice buried beneath unvegetated, unconsolidated tephra is potentially analogous to some ice deposits within regolith and pyroclasts at the Moon and Mars. Ground Penetrating Radar (GPR) is a powerful technique for both Earth and planetary surface science and can be used by future robotic and human missions to identify water ice in the subsurface of terrestrial worlds. We conducted 66 GPR surveys at Askja in August 2019 at 200 and 400 MHz to map the buried ice and overlying tephra. We used a hammer drill and auger to bore to depths of 1-1.5 m to confirm buried ice. We also performed aerial imagery surveys at each site with a Mavic 2 Pro quadcopter to document geomorphic surface expressions. Beneath the 1875 pumice, we observed interstitial ice between tephra grains at depths of ~15-30 cm and pure ice at depths of 0.6-1 m with thicknesses ranging between 2 and 3 m. Fig. 1 demonstrates the strong, continuous reflectors at the top and bottom of the ice deposit and a strong backscatter response within the pumice with an absence of scatterers within the ice layer at 200 MHz. We model attenuation through this column of material as a combination of geometric spreading and dielectric and scattering losses with frequency-dependent loss rates of 6.7 dB/m at 200 MHz and 7.2 dB/m at 400 MHz. Our investigation will provide insight into both the permafrost conditions in Iceland and an assessment of observational, analytical, and operational methods that may be transferrable to other

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/902337

2022057073 Sonnentag, Oliver (University of Montreal, Department of Geography, Montreal, QC, Canada); Riley, Emma; Vicente-Luis, Andy; Humphreys, Elyn; Marsh, Philip and Quinton, William L. Building local capacity for community-based micrometeorological monitoring [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract ED52A-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Northwestern Canada is experiencing twice the rate of climate warming compared to the rest of the Earth. A large portion of this vast region stores carbon in permanently frozen ground (permafrost). It is unclear how emissions of greenhouse gases including carbon dioxide and methane may respond to changing climate and permafrost conditions. Land surface changes (e.g., permafrost degradation) are important to local water resources and regional climate. Micrometeorological monitoring using the eddy covariance (EC) technique provides the only means to continuously measure ecosystem-scale exchanges of carbon and water and determine how the northern land surface is responding to climate change. Several million dollars have been invested over the last 15 years to develop a regional network of ten EC towers across the Northwest Territories, Canada. Travel restrictions to protect communities from Covid-19 threatens its continued operation. Here we present a recently funded training network (2021-2023) to build local capacity for community-based micrometeorological monitoring to continue operation of the EC tower network based on four components: 1) a theoretical framework is developed through virtual introductory lectures, 2) a hands-on training course provides the requisite technical skills, 3) an initial site visit to introduce site-specific logistics, health and safety protocols, and instrumental set-ups, and 4) a community-led maintenance plan in consultation with the trainees, and university and government partners. The training network engages Indigenous and non-Indigenous community members in knowledge co-creation and co-management to improve understanding of climate change impacts and support ecosystem resilience. The training network ensures that local communities are integrated into the operation of infrastructure and the associated research agendas. Many other observational research sites exist in other parts of Canada and the rest of the world. Local capacity building through knowledge co-creation and co-management between communities and subject-matter experts will increase infrastructure resilience but also increase non-expert awareness and understanding of how human activities shape ecosystem health and services in an ever more complex world.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/982508

2022057002 Spencer, Robert G. (Florida State University, Tallahassee, FL); Behnke, Megan Irene; McClelland, James W.; Tank, Suzanne; Kellerman, Anne; Holmes, Robert Max; Haghipour, Negar; Eglinton, Timothy I.; Raymond, Peter A.; Suslova, Anya; Zhulidov, Alexander; Gurtovaya, Tatiana Yu.; Zimov, Nikita; Zimov, Sergei A.; Mutter, Edda Andrea and Amos, Edwin. Pan-Arctic riverine dissolved organic matter; synchronous molecular stability, shifting sources and subsidies [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45L-1778, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Climate change is dramatically altering Arctic ecosystems, leading to shifts in the sources, composition, and eventual fate of riverine dissolved organic matter (DOM) in the Arctic Ocean. Here we examine a 6-year DOM compositional record from the six major Arctic rivers using Fourier-transform ion cyclotron resonance mass spectrometry paired with dissolved organic carbon isotope data (D14C, d13C) to investigate how seasonality and permafrost influence DOM, and how DOM export may change with warming. Across the pan-Arctic, DOM molecular composition demonstrates synchrony and stability. Spring freshet brings recently leached terrestrial DOM with a latent high-energy and potentially bioavailable subsidy, reconciling the historical paradox between freshet DOM's terrestrial bulk signatures and high biolability. Winter features undiluted baseflow DOM sourced from old, microbially degraded groundwater DOM. A stable core Arctic riverine fingerprint (CARF) is present in all samples and may contribute to the potential carbon sink of persistent, aged DOM in the global ocean. Future warming may lead to shifting sources of DOM and export through: (1) flattening Arctic hydrographs and earlier melt modifying the timing and role of the spring high-energy subsidy; (2) increasing groundwater discharge resulting in a greater fraction of DOM export to the ocean occurring as stable and aged molecules; and (3) increasing contribution of nitrogen/sulfur-containing DOM from microbial degradation caused by increased connectivity between groundwater and surface waters due to permafrost thaw. Our findings suggest the ubiquitous CARF (which may contribute to oceanic carbon sequestration) underlies predictable variations in riverine DOM composition caused by seasonality and permafrost extent.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/865199

2022056015 Spiller, Aelis (University of Alaska Fairbanks, Department of Biology and Wildlife, Fairbanks, AK); Burnett, Melanie; Kallenbach, Cynthia M.; Maranger, Roxane; Olefeldt, David; Schulze, Christopher and Douglas, Peter Munroe. Greenhouse gas emissions from permafrost peat altered by gradual drying but depends on landscape position and peat biogeochemistry [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1751, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Increasing temperatures in Arctic and Subarctic regions associated with climate change is responsible for the onset and projected increase of permafrost thaw. Coupled climate change and permafrost thaw are predicted to change the hydrology of permafrost peatlands. Such changes could have an important impact on carbon (C) and nitrogen (N)cycling, including effects on CO2 and N2O fluxes, but the direction and magnitude of these effects are not well understood. For example, some permafrost peat plateaus may experience a period of drying as water tables decline with thawing. Projected changes in precipitation patterns could also cause future drying in some thermokarst peatlands. This study explores the effect of gradual drying of peat, using a chemical drying agent, on greenhouse gas emissions and whether emissions responses to drying are as a function of landscape biogeochemical heterogeneity. In an effort to determine the response to drying across a permafrost landscape we collected samples from six positions within a sporadic permafrost landscape in northern Alberta. We measured CO2 and NO2 concentrations over time from "field wet" and "drying" peat incubations, in addition to d13C of CO2, dissolved nitrogen compounds, and peat C and N concentrations. We observed substantial variation in greenhouse gas fluxes between the landscape positions and between treatments. This study will develop key initial findings of the effect of drying on permafrost peat C and N cycling that will inform future research on this important environmental process.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/948281

2022059989 Steinmann, Rene (ISTerre Institute of Earth Sciences, Saint Martin d'Heres, France); Seydoux, Leonard and Campillo, Michal. Revealing the signature of ground frost in continuous seismic data with machine learning [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract S54A-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

We study how ground frost affects the ambient seismic wavefield recorded by a three-component broadband sensor. By applying machine learning algorithms on continuous seismic data, we can retrieve the seismic signature of the continuous freeze and thaw process at the surface of the ground. The retrieved signature reveals that the presence of ground frost imprints the amplitude of the ambient seismic wavefield, and the energy ratio between horizontal and vertical components (H/V). A regression model can even predict diurnal freeze and thaw patterns based on the seismic data. Thus, we assume that slight changes in the physical properties of the frozen surface, such as the thickness, alter the seismic wavefield. Models of the subsurface with different properties of the ground frost agree with the observations from the field. The penetration depth of the ground frost, the temperature of the frozen ground, and the presence of different modes in the wavefield determine how the seismic wavefield is changing. The findings of this study show the potential of a single seismic station for monitoring frozen bodies near the surface, such as permafrosts.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/836285

2022056023 Stokes, Murray (University of Tennessee, Knoxville, TN); Green, Brianna; Abramov, Andrey; Vishnivetskaya, Tatiana A.; Sipes, Katie; Lloyd, Karen G. and Steen, Andrew D. Extracellular enzyme activities and mineralogy of thawing permafrost soils near Bayelva, Svalbard [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45K-1759, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Thawing Arctic permafrost soils have the potential to act as globally important sources of carbon dioxide and methane. Soils in Svalbard are characterized by low organic carbon content and particularly rapid thawing rates, making them distinct from more well-studied soils in Arctic Alaska and Siberia. Because most bioavailable organic carbon in soils is in the form of macromolecules, heterotrophic microbes must degrade this outside of the cell prior to respiration or fermentation. Thus, the set of extracellular enzymes present in soils yields insight into the nature of organic carbon demand by the in situ community. This demand is intimately linked to soil mineralogy, which controls the extent to which microbial enzymes and macromolecules sorb to mineral surfaces. Here, we report measurements of the potential activities of extracellular glycosylases (polysaccharide-degrading enzymes), peptidases (protein-degrading enzymes) and alkaline phosphatase, in relation to phyllosilicate mineralogy of soils from four sites near Bayelva, Svalbard. Results will indicate the degree to which soil mineralogy influences organic carbon demand in these low-organic carbon permafrost soils.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/900220

2022059925 Streletskiy, Dmitry A. (George Washington University, Washington, DC); Lanckman, Jean-Pierre F.; Clemens, Sonia; Suter, Luis; Shiklomanov, Nikolay I. and Nyland, Kelsey E. Estimating costs of mid-21st century climate change impacts on societies and infrastructure in the circumpolar Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55E-0477, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Arctic climate has been warming 2 to 3 times faster than global average rate with significant impacts on ecosystems and northern communities by disrupting subsistence practices, limiting accessibility, and putting infrastructure at risk. We examined the spatial patterns of projected climate and environmental changes and their impacts on infrastructure and population in the Arctic states by the mid-21st century using a subset of CMIP6 models under the SSP855 scenario. Arctic states and municipalities therein were ranked according to the magnitude of projected changes to air temperature, precipitation, permafrost and their effects on infrastructure stability, transportation accessibility, and energy use. Svalbard, Alaska, the Northwest Territories, Yukon, and the Yamal-Nenets Autonomous Okrug were among the regions projected to experience the greatest changes. Socio-economic and infrastructure data were used to evaluate the economic costs associated with such change on various types of infrastructure at both state and municipal levels. The approach presented in this study allows to communicate complex climatic information in widely accessible graphs and maps that can be used by a diversity of stakeholders and policymakers interested in the development of Arctic adaptation and mitigation strategies.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/832386

2022059963 Sullivan, Taylor D. (University of Wyoming, Laramie, WY); Parsekian, Andy; Saari, Stephanie; Barker, Amanda J. and Wagner, Anna M. Temperature dependence of borehole NMR-sensed soil moisture in permafrost regimes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS11A-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Alaskan permafrost continues to experience widespread thawing and degradation as high-latitude regions warm, and such changes forebode substantial consequences to infrastructure and biogeochemical cycles. Projections of the fate of this permafrost depend on accurate assessment of current surface and subsurface conditions and the ability of models to approximate subsurface mass and heat transport subject to surficial stimuli. Repeatable, non-invasive, high-fidelity soil moisture quantification remains of the utmost importance for ecosystem models as soil moisture within the active layer of permafrost critically influences energy exchange at the upper boundary of permafrost. Nuclear magnetic resonance (NMR), sensitive to the spin magnetic moment of protons within the nucleus of Hydrogen atoms, is a useful technique for quantifying soil moisture in permafrost systems. Borehole-NMR continues to grow in prevalence in permafrost literature, although permafrost-specific applications of the technique require special consideration due to low temperatures in and near permafrost. This study investigates the temperature dependence of a borehole-NMR system in a water tank at temperatures spanning -18 to +18°C within a cold room. Our results indicate overestimation of water content up to 18% in bulk water and demonstrate that probe temperature is independent of this overestimation. Using this new understanding of temperature dependence, we apply depth-specific soil moisture scaling-informed by the soil temperature profile-on NMR-sensed soil moisture water contents from the active layer of a riverine ecotype adjacent to the Chena River on Fort Wainwright, Alaska. This work has implications for future applications of NMR surveys in permafrost and the reduction of uncertainty in upscaling soil moisture observations from the borehole to the landscape scale.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/984440

2022055982 Talucci, Anna (Colgate University, Department of Geography, Hamilton, NY); Loranty, Michael M. and Alexander, Heather Dawn. Fire regimes across eastern Siberian taiga and tundra from 2001-2020 [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B23C-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Circum-boreal and -tundra systems are crucial carbon sinks that are experiencing amplified warming and are at risk of increased wildfire activity. Changes in wildfire extent and severity have broad implications for vegetation dynamics, underlying permafrost soils, and ultimately, carbon cycling. However, understanding wildfire effects on biophysical processes across eastern Siberian taiga and tundra remains challenging because of the lack of a readily accessible annual fire perimeter database and underestimation of area burned by MODIS satellite imagery. To better understand wildfire dynamics over the last 20 years in this region, we mapped area burned, generated a fire perimeter database, and characterized fire regimes across eight ecozones spanning 7.8 million km2 of eastern Siberian taiga and tundra from » 61-72.5°N and 100°E-176°W using the Landsat archive, processed via Google Earth Engine (GEE). We generated composite images for the annual growing season (May - September), which allowed mitigation of missing data from snow, clouds, and the Landsat 7 scan line error. The annual composites were used to calculate the difference Normalized Burn Ratio (dNBR) for each year. We converted annual dNBR images to binary burned or unburned imagery that was used to vectorize fire perimeters in GEE. We mapped 22,110 fires that burned 150.5 million hectares (Mha) over 20 years. We quantify fire regime attributes such as annual area burned, fire density, and fire season length, and then we evaluate the influence of climate factors on annual area burned. Although 2003 was the largest fire year recorded, 2020 was an extreme fire year for four of the northeastern ecozones resulting in increased fire activity above the Arctic Circle. The climate water deficit had the most influence on annual area burned of all climate factors indicating that as conditions become drier, area burned rises. Increases in fire extent, severity, and frequency with continued climate warming will impact vegetation and permafrost dynamics with an increased likelihood of irreversible permafrost thaw leading to increased carbon release and/or conversion of dominant vegetation types.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/818963

2022055967 Tang, Jing (Lund University, Department of Physical Geography, Lund, Sweden); Zhou, Putian; Miller, Paul A.; Schurgers, Guy; Gustafson, Adrian; Makkonen, Risto J.; Fu, Yongshuo H. and Rinnan, Riikka. Vegetation shifts trigger strong local BVOC impacts on atmospheric aerosols in high latitudes [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1437, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The amplified warming in high latitudes will likely cause continual large changes in vegetation composition and plant productivity, which could profoundly alter plant emissions of Biogenic Volatile Organic Compounds (BVOCs). The impacts of the short-lived BVOCs on the climate system in this region are largely uncertain due to the scarcity of emission data and/or underrepresented plant variations. We explored historical and future changes in the emissions of dominant BVOCs, isoprene and monoterpenes, from boreal and tundra regions using a dynamic vegetation model, LPJ-GUESS. The model has integrated the latest BVOC observations and has detailed representations of tundra vegetation, permafrost and wetlands. For the future (i.e., 2015-2100), we selected 15 CMIP6 climate predictions to drive LPJ-GUESS, and ran different factorial experiments to assess the relative importance of climatic drivers, vegetation changes, atmospheric CO2, and nitrogen availability in determining future BVOC emissions. The modelled BVOCs from LPJ-GUESS were fed into global chemistry transport model version 5 (TM5) to assess future BVOC impacts on the atmospheric Secondary Organic Aerosol (SOA). The results showed a clear increase in isoprene emission, but a moderate increase or a decrease of monoterpene emissions under different future scenarios. For the regions where boreal needle-leaved evergreen trees (monoterpene-emitters) are overtaken by broad-leaved deciduous trees (isoprene-emitters), we see strong decreasing trends for monoterpenes. The predicted northward movement of boreal needle-leaved trees is associated with strong increasing trends of monoterpenes in northern Canada and Russia. The factorial experiments revealed that under a low CO2 emission scenario, the positive trends in isoprene emission were largely driven by vegetation shifts, while under a high CO2 emission scenario, the trends were determined by plant CO2 fertilization, vegetation changes and CO2 inhibition of isoprene synthesis. The TM5 results showed that the future increased BVOC emissions from the high latitudes strongly increased surface SOA concentrations and resulted in up to 30% increases in SOA load and optical depth at 550 nm. The feedbacks on SOA were spatially linked to the altered monoterpene emissions caused by shifted vegetation.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/884306

2022057071 Tao, Jing (Lawrence Berkeley National Laboratory, Berkeley, CA); Zhu, Qing; Riley, William J.; Bisht, Gautam; Eklof, Joel and Neumann, Rebecca Bergquist. The role of advective heat transfer in affecting permafrost thaw and methane emissions at a hillslope thermokarst bog [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-10, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Recent Arctic amplification has warmed permafrost unprecedently, causing widespread thermokarst formation, especially over discontinuous and sporadic permafrost regions. At the Alaska Peatland Experiment (APEX) site (i.e., a hillslope thermokarst bog interior Alaska), measurements have shown rapid permafrost thaw and new thermokarst formation at the bog edges. Moreover, chamber measured methane (CH4) emissions from the bog areas demonstrated large heterogeneity, showing greater emissions from newly formed thermokarst at bog edges than bog centers. We hypothesize that the advective heat transfer associated with water flow plays an important role in affecting permafrost thaw and bog CH4 emissions. Specifically, rainfall-induced infiltration flux and subsurface vertical water fluxes advect heat to the permafrost table; Laterally, groundwater flow transports heat from upland peat to lowland bog areas, warming permafrost at bog edges and deepening the active layer, which, in turn, facilitates more lateral water flow from upland. However, current land models usually only represent vertical heat diffusion resulted from subsurface soil temperature gradient and could not well reproduce the lateral heterogeneity in soil temperature, water table, and CH4 emissions. Through coupling water and heat transport vertically and laterally within the Energy Exascale Earth System Model (E3SM) land model (ELMv1), we demonstrated the critical role of advective heat transport in affecting permafrost thaw, bog plant productivity, bog-area inundation, and thus CH4 emissions. Specifically, along two simulation transects extending from upland forest permafrost to the lowland thermokarst bog, results that incorporated advective heat transport showed improvements in simulated soil temperature and moisture profiles, the active layer thickness, and the bog area inundation dynamics. Consequently, simulation results reasonably reproduced the observation-based heterogeneity of CH4 emissions along the transects. We also demonstrated that the coupled water and heat transport 1) controls the onset timing of soil spring thaw, 2) affects the zero-curtain periods during fall via influencing soil freezing, and 3) significantly impacts the peak time and magnitude of bog CH4 emissions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/879355

2022057063 Tape, Ken D. (University of Alaska Fairbanks, Fairbanks, AK); Brown, Caroline; Jones, Benjamin M. and Clark, Jason. Arctic Beaver Observation Network (A-BON); tracking a new disturbance regime [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-02, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Beavers (Castor canadensis, C. fiber) are ecosystem engineers and a keystone species with wide-ranging effects on ecosystem structure, dynamics, and services. Since publishing our remote sensing evidence showing that beavers are colonizing tundra regions, numerous scientists, land managers, and Indigenous representatives have approached us with concern about beaver engineering and directions for future research. People in remote communities have observed the influx of beavers in real-time, with concern about water quality, fish, and boat access. Because beavers impact nearly every aspect of lowland arctic ecosystems, baseline information about beaver presence and activity on the landscape is needed to support a wide range of potential projects, from permafrost thaw modeling and carbon cycling to eDNA, aquatic food webs and fish, tundra ecology and vegetation, to issues of water quality and boat access, and finally to management and adaptation. We plan to map beaver ponds in the circumarctic during the coming years, and to put those ponds in the context of other hydrologic and permafrost changes.In August 2020, we founded A-BON and established working groups for Alaska, Canada, Europe, and Asia. The group currently includes scientists, local people, tribal entities, state and federal agencies, and is developing ties with national and international monitoring groups and steering committees such as IASC, IARPC, and CAFF-CBMP. The first in-person A-BON meeting is planned for March 15-18, 2022 in Fairbanks, Alaska. Anyone with interest in lowland tundra ecosystems and the downstream implications of beaver engineering is encouraged to join A-BON and attend the upcoming meeting.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/831660

2022059917 Teufel, Bernardo Stephan (McGill University, Montreal, QC, Canada) and Sushama, Laxmi. High-resolution modelling of climatic hazards relevant for the northern transportation sector [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC32C-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Infrastructure and transportation systems on which northern communities rely are exposed to a variety of climatic hazards over a broad range of scales. Efforts to adapt these systems to the rapidly warming Arctic climate require high-quality climate projections. Here, a state-of-the-art regional climate model is used to perform simulations at 4-km resolution over the eastern and central Canadian Arctic. These include, for the first time over this region, high-resolution climate projections extending to the year 2040. Validation shows that the model adequately simulates base climate variables, as well as variables hazardous to northern engineering and transportation systems, such as degrading permafrost, extreme rainfall, and extreme wind gust. Added value is found against coarser resolution simulations. A novel approach integrating climate model output and machine learning is used for deriving fog - an important, but complex hazard. Hotspots of change to climatic hazards over the next two decades (2021-2040) are identified. These include increases to short-duration rainfall intensity extremes exceeding 50%, suggesting Super-Clausius-Clapeyron scaling. Increases to extreme wind gust pressure are projected to reach 25% over some regions, while widespread increases in active layer thickness and ground temperature are expected. Overall fog frequency is projected to increase by around 10% over most of the study region by 2040, due to increasing frequency of high humidity conditions. Given that these changes are projected to be already underway, urgent action is required to successfully adapt northern transportation and engineering systems located in regions where the magnitude of hazards is projected to increase.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/873712

2022059991 Timm, Kristin (University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK) and Dann, Julian. The cryosphere and climate change communication; messengers, messages, and outcomes of framing climate change as thawing ice [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract SY45A-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Whether it's a calving glacier, a thaw slump in the permafrost, or disappearing sea ice--dramatic changes and dynamic processes in the cryosphere have had a prominent place in how scientists, the news media, film makers, and others talk about the effects of climate change communication. This strong, sometimes emotional imagery, and the relatively easy to understand relationship between heat and ice makes glaciers, sea ice, and permafrost helpful for communicating about climate change. However, their position on the globe, away from major population centers could also reinforce the perception that climate change is a problem that predominantly affects the Arctic, Antarctic, and alpine areas--and not mid-latitudes. Through a systematic review of the academic literature on climate change communication, we synthesize the extent to which the cryosphere is a characteristic of messages about climate change, the types of communicators and messengers who use this framing, and the effects of emphasizing the cryosphere in climate change communication on different audiences. This synthesis will identify areas of agreement and gaps in our understanding about how centering the cryopshere in climate change communication ultimately affects the way audiences think about climate change. This review will also propose evidence based, practical guidance for science and climate change communicators, so that their efforts to highlight the changing cryosphere lead to better and productive communication with their audiences.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/989210

2022059928 Tolmanov, Vasiliy Andreevich (Michigan State University, East Lansing, MI); Grebenets, Valery I. and Sokratov, Sergey A. Snowbank impacts on frozen foundations in cities of continuous permafrost zone [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55E-0480, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Increasing winter air temperatures in the Russian Arctic enhances the influence of snow on the permafrost system via the ground thermal and moisture regimes, particularly within the active layer and near-surface permafrost. Many settlements lack consistent and systematic monitoring of snow in permafrost zones. We observed the warming effect of snowbanks on piling foundations in the cities located in continuous permafrost zone of Russia. For example, the long-term average snow depth in natural areas within the Greater Norilsk Region is 0.7 m, but depths can reach 2 m in topographic lows (data from the Norilsk Meteorological observatory and CALM R-32 Site). However, snowbanks in the city range from 2 to 5 m from ploughing and consistently accumulate in the same locations in residential building courtyards. The size and location of these artificial snowbanks in the cities are influenced by urban topology, ploughing techniques in addition to annual snowfall. Numerical simulations indicate progressive increases in ground temperature in response to snow accumulation up to 2.5 m and >2.5 m does not have a significant impact on ground insulation. While persistent snowbanks surrounding buildings do not contribute to increased insulation, they negatively impact piling foundations by blocking ventilation in winter. Without wintertime cold air circulation under buildings, permafrost warms leading to foundation degradation. A comparison of ground thermal surveys conducted in the 1970s and 2010s shows that 30-40% of building foundations in the city of Norilsk have significantly warmed and now exhibit structural deformation. This work was supported by the RFBR project 18-05-60080 "Dangerous nival-glacial and cryogenic processes and their impact on the infrastructure in the Arctic".

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/927774

2022056018 Toohey, Ryan (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Mutter, Edda A. and Herman-Mercer, Nicole Michelle. Regional ground water and surface water interactions due to changing active layer dynamics in the Yukon River basin [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45J-1754, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In this presentation, we discuss the groundwater and surface water biogeochemical dynamics in conjunction with a dynamic active layer response within different regions of the Yukon River Basin (YRB). Leveraging historical data from the United State Geological Survey (USGS) and the Indigenous Observation Network, a partnership between the Alaska Tribes and Yukon First Nations, the Yukon River Inter-Tribal Watershed Council, and the University of Alaska, Fairbanks (UAF), hydrological analysis indicates that the Yukon River has been changing over the last forty years with a relatively unchanged annual discharge due to increasing groundwater contributions. Large scale permafrost degradation, within the predominantly discontinuous permafrost YRB, has been hypothesized as one of the reasons for increasing groundwater contributions. Our active layer, soil temperature and soil moisture data appear to support this theory. At the same, multi-decadal increases of annual fluxes of weathering ions have also been observed within the Yukon to support the hypothesis of increasing groundwater as the result of permafrost degradation. Seasonally, biogeochemical changes present a more complex picture with results showing large increases of weathering ions during an earlier break up and longer freeze up seasons. Over the past 20 years, throughout the YRB, the active layer appears to be thickening with seasonal correlation between weathering ions, DOC and O18 dynamics with longer periods of unfrozen soil moisture and increased temperatures within the active layer. Historical flux modeling results for a variety of different regions within the YRB will be presented with a discussion on some potential reasons for these differences. Important regional differences in geochemistry and active layer parameters linked to permafrost continuity and tributaries will be highlighted. Changing biogeochemistry and active layer dynamics of the YRB may have important implications for the global effort to characterize arctic river fluxes as they relate to permafrost dynamics, the carbon cycle, aquatic ecosystems, and contaminant transport.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/861717

2022057007 Treat, Claire C. (Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Potsdam, Germany); Jones, Miriam; Brosius, Laura; Grosse, Guido; Anthony, Katey M. Walter and Frolking, Steve E. Methane emissions from northern wetlands during the Holocene; a synthesis approach to account for wetland expansion and fen-bog-permafrost transitions [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B53D-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Methane emissions from northern high latitude wetlands constitute a major uncertainty in the atmospheric methane (CH4) budget during the Holocene. To reconstruct northern wetland methane emissions, we used an empirical model based on syntheses of observations of peat initiation from more than 3600 radiocarbon-dated basal peat ages, plant-macrofossil-derived peatland type from more than 250 peat cores from sites across the northern high latitudes, and observed CH4 emissions averaged from modern-day wetland types in order to explore the effects of wetland expansion and changes in wetland type. Peatland basal ages and plant macrofossil records showed the widespread formation of fens in major northern wetland complexes before 8000 BP. After 8000 BP, new fen formation continued, but widespread peatland succession (to bogs) and permafrost aggradation also occurred. Reconstructed CH4 emissions from peatlands increased rapidly between 10,600 BP and 6900 BP due to fen formation and expansion, then stabilized after 5000 BP at 42±25 Tg CH4 y-1, as high methane-emitting fens transitioned to lower methane-emitting bogs and permafrost peatlands. Permafrost formation in northern peatlands after 1000 BP decreased CH4 emissions by 20% to 34±21 Tg y-1 by the present day. Warming temperatures, changes in peatland hydrology, and permafrost thaw will likely change the magnitude of northern peatland emissions in the future.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/865879

2022059940 Triplett, Amanda (University of Arizona, Tucson, AZ) and Condon, Laura E. Exploring the impacts of warming induced cryosphere changes on watershed dynamics in the Heihe River basin [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H25S-1237, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Heihe River Basin in Northwestern China depends heavily on manmade and natural storage like surface reservoirs, rivers, and groundwater for economic and environmental functions. The Qilian Mountain cryosphere in the upper basin is integral to supporting streamflow and recharging these storage supplies. Climate change driven shifts in high elevation water storage are expected to have significant impacts on water supply in the Heihe River Basin. Due to warming temperatures, glaciers are projected to disappear and significant permafrost area is expected to degrade into seasonally frozen ground over the next several decades. This deglaciation reduces streamflow in the thawing season (April to October) while permafrost degradation increases base flow in the freezing season (November to March). To examine the impacts of these shifts, we built a fully integrated hydrologic model using ParFlow-CLM of the middle basin, which encompasses over 90% of total water usage in the basin. Using this model, we ran several decadal simulations (2001 to 2011) to examine possible outcomes from deglaciation and advanced permafrost degradation. These scenarios decrease surface flow inputs from the upper basin in the thawing season, and increase them in the freezing season by varying fractions to model the possible range of outcomes from the system changes outlined above. The scenario results are examined for the impact of streamflow input changes on watershed dynamics in the middle basin, including surface and groundwater storage, infiltration and evapotranspiration. Ultimately, this analysis can be used to examine the cascading impact of climate change in the cryosphere on the resilience of water resources in arid basins downstream of mountain ranges globally.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/948391

2022057051 Turetsky, Merritt R. (University of Colorado at Boulder, Institute of Arctic and Alpine Research, Boulder, CO); Cox, William; Dieleman, Catherine M.; Grosse, Guido; Koven, Charles and Lawrence, David M. The future of community- and policy- relevant thermokarst research; lessons learned and a call to action [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-01, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Several decades of research have provided insight into patterns of and controls on thermokarst initiation and expansion, yet studies tend to focus on individual types of thermokarst (i.e., thaw lake formation and subsequent drainage) in particular regions. Today, we are left with uneven knowledge about abrupt permafrost thaw both conceptually and regionally. The goal of this presentation is to summarize recent advancements in monitoring thermokarst and its impact on soil, vegetation, and water while also framing a call to action for the next decade of research. Over the next decade, permafrost researchers must align their efforts on several fronts to not only increase our knowledge about changing permafrost but to align this knowledge with key community and policy needs. To support climate change planning and adaptation, northern communities need future thaw vulnerability mapped at scales relevant to their needs, which will require a suite of downscaled and new mapping and remote sensing products. Thermokarst predisposition maps based on circumpolar datasets greatly overestimate the area vulnerable to thermokarst, which can lead to poor planning and climate anxiety. In some situations, existing mapping products may be useful for downscaling with more detailed input data. In other situations, entirely new approaches may be required to support local action. A second key need for community relevant research is the ability to detect and monitor early warning indicators of thermokarst. Such information is needed to support scenario planning and to help mitigate the risks to social, cultural, and physical infrastructure created by permafrost change. We are evaluating the potential for using changes in vegetation, wetting/drying and topography as early warning indicators of thermokarst, all of which can be remotely sensed. Finally, integrating fine-scale disturbances such as thermokarst into large scale models remains a key challenge but critical for supporting sound climate policy. While a diversity of permafrost modeling approaches is necessary, we outline guiding principles that will help enhance model comparisons, assimilation of simulated data across spatiotemporal scales, and the ability for policy decisions to be rapidly informed by emerging science on permafrost change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/970192

2022059930 Turner, Matthew (University of New Hampshire, Department of Civil, and Environmental Engineering, Durham, NH); Harris, Michael; Ghayoomi, Majid; Brewer, Jennifer; Duderstadt, Katharine; Kholodov, Alexander L. and Shiklomanov, Alexander I. Connecting climate change and seismic resilience of Alaskan infrastructure systems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract GC55J-0529, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Alaska is one of the most seismically active areas in the world, with the region accounting for about 10% of the world's recorded seismic events. In recent years, the state has experienced some of the largest recorded earthquakes in history, including the 1964 Great Alaskan earthquake, the 2002 Denali earthquake, and the 2018 Anchorage earthquake. Coincidently, the state has seen some of the most drastic changes resulting from climate change. Compared to the rest of the United States, Alaska has warmed twice as rapidly. Climatic driven temperature changes pose a threat to the permafrost distribution throughout the Arctic and sub-Arctic regions of Alaska. Thawing permafrost may impact the seismic risk of Alaskan communities and the performance of built infrastructure systems during seismic events. As part of a preliminary investigation to understand the connection between climate change and seismic risk throughout Alaska, a series of key informant interviews were conducted. Informants were selected using a combination of purposive and chain-referral sampling methods and included engineers, disaster management specialists, seismologists, and town planners living or working in the region. Data analysis was performed using a modified grounded theory approach. Tentative findings from this study thus far include: (1) The study sheds light on the seismic resilience capacities and challenges throughout various regions of Alaska, specifically related to the state's sparse population and physically isolated communities; (2) Enhanced seismic monitoring throughout Arctic regions could further characterize the seismic hazard for potential integration into a statewide earthquake early warning system; (3) Implementation of the International Building Code is a topic of concern to enhance seismic resilience; (4) Engineers need to consider the influence of permafrost thaw on the seismic performance of built infrastructure systems or develop novel systems to enhance the lifespan of underlying frozen soils; (5) Indigenous communities and villages, who have watched the land for many lifetimes, may have viable and untapped knowledge systems to better understand changing soil conditions throughout Arctic and sub-Arctic Alaska.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/842284

2022055990 Valentini, Emiliana (Italian National Research Council, Institute of Polar Sciences, Rome, Italy); Piedelobo, Laura; Taramelli, Andrea; Sapio, Serena; Salzano, Roberto and Salvatori, Rosamaria. Biophysical fractional cover (FCover) composition retrieval in Svalbard Islands with the new generation of satellite sensors [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B25E-1499, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic ecosystems are pathways and receptors to climate change effects, especially to the rising temperature that is altering the duration of seasonal snow and ice cover patterns. Measuring changes of light absorption and reflectance allows to track the gradients across biophysical properties and provides proxies to understand the cumulative effects on wildlife habitats and human mobility.The new generation of satellite sensors for Earth Observation supports the identification of key monitoring Essential Biodiversity Variables (EVs) and gives insight into the ecosystems discontinuities and emergent properties induced by climate change. Spanning a spatial resolution of 30 to 5 meters and a large amount of hyperspectral bands, PRISMA (Hyperspectral Precursor of the Application Mission), launched in 2019 by the Italian Space Agency, is the only orbiting hyperspectral satellite sensor and it provides images over the latitudes of 79° N. The showcase of the Svalbard Islands (Norway), is used to test the chance of mapping the Fractional Cover (FCover) composition of the landscape over different seasons and to improve the estimation of common Essential Variables for vegetation, substrates, water, snow and ice. The biophysical products obtained describes a wide range of features that can be associated not only to structures and functions of the ecosystems but also to the provision of ecosystem services, such as those related to the water quality and Carbon storage. The discussion is on the chance of reinforcing existing Essential Biodiversity Variables, with proxies for modeling the distribution of the habitat types and the Carbon cycling and it is also on the availability of direct observations for the permafrost and vegetation patterns, the snow seasonality, inland and coastal waters quality.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/932433

2022055987 Virkkala, Anna-Maria (Woodwell Climate Research Center, Falmouth, MA); Rogers, Brendan M.; Watts, Jennifer; Natali, Susan; Burrell, Arden; Mauritz, Marguerite; Potter, Stefano; Savage, Kathleen E. and Schuur, Edward. Understanding the drivers, dynamics, and regional patterns of terrestrial ecosystem CO2 fluxes across the Arctic-boreal zone [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24D-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic-Boreal Zone (ABZ) is experiencing rapid changes with pronounced impacts on the terrestrial carbon cycle due to climate change. Non-growing season carbon emissions have recently been shown to be larger than previously thought. On the other hand, growing season plant productivity and carbon uptake are increasing in areas that are not undergoing major disturbances related to fires, permafrost thaw, and drought. Despite the importance of these ABZ fluxes for global carbon budgets, we lack a comprehensive understanding of their dynamics that would integrate the extent, magnitude, and drivers of these fluxes and their changes in different seasons and regions. Here, we aim to fill this knowledge gap by studying the drivers and spatiotemporal patterns of spring, summer, autumn, and winter carbon dioxide (CO2) fluxes and budgets. We use a recently compiled database of monthly Arctic-Boreal terrestrial ecosystem CO2 fluxes (ABCflux, n=6309) and upscale fluxes across the ABZ over the past four decades using machine learning models and a wide array of geospatial data describing, for example, climate, snow, vegetation, soil moisture, and disturbance conditions. We present maps of gross primary productivity, ecosystem respiration, and net ecosystem exchange aggregated over monthly intervals at 1 km spatial resolution from 2000 to 2020 and 8 km from 1981 to 2017. We use these maps and site-level information to synthesize recent changes in ABZ CO2 fluxes, their sensitivity to various environmental conditions, and what these mean for the CO2 uptake strength of this region in the near future.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/932330

2022057081 Vulis, Lawrence M. (University of California Irvine, Department of Civil and Environmental Engineering, Irvine, CA); Tejedor, Alejandro; Zaliapin, Ilya V.; Rowland, Joel C. and Foufoula-Georgiou, Efi. The relationship between lake spatial distribution and permafrost processes on Arctic deltas [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP31B-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

River deltas ringing the Arctic Ocean coastline are characterized by thermokarst lakes, i.e. perennial depressions that grow by the thaw of ice-rich soil. These lakes trap and store riverine freshwater, sediment, and nutrients, thereby modulating the timing and magnitudes of riverine fluxes to the Arctic Ocean. Average lake size has recently been reported to be inversely related to mean annual air temperature on arctic deltas, suggesting a projected reduction of mean lake size under global warming with implications for delta morphology and arctic ecohydrology. In this study we extend our analysis to examine spatial patterns of lake spacing under the expectation that local lake density (i.e. "local lake packing" and lake-to-lake distances) can provide physical insight into delta evolution in permafrost environments. We assess lake packing at the individual lake, island, and delta scale on 12 arctic deltas across Siberia, Alaska, and Canada, and identify coherent areas (i.e. clusters) of lakes with similar packing within individual deltas. Clusters of highly packed lakes are attributed to ice rich soils, while differences in geomorphic processes in delta formation (i.e. fluvial, wave, and tidal activity) may also play an important role. Under projected 21st century warming and permafrost thaw, our results suggest that lake cover will generally transition from finely to coarsely packed across all deltas, with variability within and across deltas driven in part by differences in local geomorphic processes and ice volume. These results will help to constrain projections of future delta morphology in regions prone to permafrost thaw, with implications for riverine freshwater, sediment, and carbon flux delivery to the Arctic Ocean.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/936019

2022057069 Vural, Deniz (Scientific and Technological Research Council of Turkey, Polar Research Institute, Kocaeli, Turkey) and Vural Yavuz, Enver. The warming Arctic; the roles of thermokarst lakes in permafrost terrestrial ecosystems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C55E-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The average global temperature has increased by more than 1°C since 1900 while the Arctic region has warmed by about 2°C within the same time. This warming differential between the entire globe and polar regions (specifically Arctic) caused the Arctic amplification. The Arctic environments are already altered as a result of this strong amplification of global warming that the rate of permafrost thawing is accelerating in the Arctic and the region becomes more susceptible to further thawing. Permafrost, which occupies approximately 25% of the land area in the Northern Hemisphere, is one of the key components of the terrestrial ecosystem in the cold areas. Over the past 14,000 years of post-glacial times, the thaw of ice-rich permafrost, which leads to thermokarst formation, has been one of the main geomorphic processes operating in the Arctic. Additionally, Arctic lowlands are characterised by great numbers of small water bodies, which are also known to affect not only surface energy budget, but also global carbon cycle. Therefore, thermokarst lakes are the net greenhouse gas sources as century old carbon deposits become bioavailable and are mineralized to CH4 and CO2. Thermokarst, the most widespread terrain-type of abrupt thawing of ice-rich permafrost, occurs when soil warming melts ground ice and following land surface collapse. Thermokarst lakes or thaw lakes are typical forms of permafrost degradation and are linked to surface disturbance, subsequent melting of ground ice, as well as positive feedback between lake growth and permafrost thaw. This study focuses on literature review of thermokarst lakes figured in lowland permafrost zones, investigating the widespread lake formation and spatial evolution of thermokarst landscapes that will help understand the relationship with waterbody differentiation and change in the carbon pool which can be another motivation for further analyses on feedback mechanisms to the warming climate in the Arctic.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/980735

2022059982 Wadhams, Jane (Florida State University, Department of Earth, Ocean, and Atmospheric Science, Tallahassee, FL); Newby, Sean; Them, Theodore R. and Owens, Jeremy D. Rapid decline in global marine oxygen during carbon excursion of the Paleocene-Eocene Thermal Maximum (PETM) [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract PP25F-0991, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The geologically instantaneous release of massive quantities of isotopically light carbon during the most recent abrupt climate perturbation, the Paleocene-Eocene Thermal Maximum (PETM; ~55.9 Ma), makes it the best and most recent analog to better understand future climate scenarios. There is a negative carbon isotope shift that suggests a major perturbation to the global carbon cycle due to an abrupt release of isotopically light carbon from various sources of methane. The large addition of carbon to the ocean-atmosphere system likely caused a cascade of events that started extreme warming and had additional impacts such as ocean acidification, permafrost loss, and a small increase in global euxinia (anoxia with sulfide in the water column). There is, however, limited evidence for widespread deoxygenation leading to enhanced burial of organic carbon, which contrasts the PETM to other periods of oceanic anoxic events (OAEs). This research aims to better constrain the global spatiotemporal redox structure across the PETM global oceans using both novel and traditional geochemical tools. We analyzed samples from the Arctic (IODP Expedition 302, Site M0004-A) and the North American Atlantic Coastal Plain (Cambridge-Dorchester Airport) using geochemical proxies including trace metal concentrations, iron speciation, and thallium isotopes to constrain the local and global redox conditions throughout the PETM. Trace metal and iron speciation proxies tracking local conditions suggest that the Arctic experienced persistent euxinia while the Atlantic Coastal Plain maintained an anoxic water column during the PETM. Thallium isotopes--a new global proxy that responds to the global burial of manganese oxides for short-term events and thus tracks the earliest marine (de)oxygen perturbation--record a rapid loss of global oxygen that appears to recover before the carbon isotope record returns to pre-event values. This suggests that marine anoxic seafloor area expanded during the initial phase of the PETM. An expansion of deoxygenation from the PETM provides a template for warming events and thus has important implications for modern and future anthropogenic warming scenarios.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/958885

2022059968 Wagner, Anna M. (U. S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK); Sullivan, Taylor D.; Glaser, Dan R., II; Hiemstra, Christopher A.; Saari, Stephanie; Broberg, Kate Liddle and Gelvin, Arthur. Permafrost degradation delineation using a multi-faceted geophysical surveying approach [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS15A-0362, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Atmospheric warming and enhanced liquid precipitation are increasing soil temperatures and lengthening sub-Arctic and Arctic summer growing seasons, leading to widespread permafrost degradation and ecological changes across boreal and tundra biomes. The deepening seasonally-thawed active layer affects soil biogeochemical processes, hydrological processes, vegetation dynamics, and microbial activity. We investigated ongoing permafrost degradation in Fairbanks, Alaska using a multi-faceted approach that included historical and recent geophysical and frost-probing surveys and analyses. Past ground penetrating radar (GPR), electrical resistivity tomography (ERT), and capacitively coupled resistivity (CCR) geophysical surveys were completed in 1993-1994 and again in 2010 to aid in constructing a conceptual permafrost model. Many of the transects were revisited in 2020-2021, and additional GPR and ERT data were acquired to assess changes in permafrost continuity since 2010. Further, lidar terrain surface differencing and corresponding hydrological comparisons were completed to quantify changes from 2010 to 2017 in our study area. High-resolution visible satellite imagery time-series comparisons (2002-present) were done to examine temporal changes.Subsidence of about 20-50 cm was observed at a number of locations throughout the study domain. These areas indicate likely changes to watershed boundaries and stream channels and heterogeneous impacts within the study area. A preliminary comparison of ERT data between 2010 and 2021 suggests a reduction in permafrost extent along at least one of the transects. The next data processing steps include interpolation of permafrost characteristics in preparation for informing near-surface permafrost maps and 3D permafrost distribution.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/985394

2022059970 Wagner, Natalie (University of Arizona, Department of Geosciences, Tucson, AZ); Holt, John W.; Christoffersen, Michael; Tober, Brandon; Kuehn, Tyler; Mooneyham, Sydney; Truffer, Martin; Fahnestock, Mark A.; Devaux-Chupin, Victor; Loso, Michael and Thompson, Anna. Characterization and confirmation of ground ice in the Malaspina Forelands, Alaska through transient electromagnetic methods, satellite imagery, and historical records [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS15A-0367, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Malaspina Glacier forelands are a complex and active periglacial environment forming a relatively narrow barrier between the glacier and the ocean. A majority of the forelands was only recently exposed due to the glacier's retreat, leaving behind landforms such as ice-cored moraines, debris-covered massive ice, proglacial lakes, river outwash plaines, and developing thermokarst lakes. Satellite imagery from the past 50 years has shown many of these landforms are melting and degrading into expanding lakes, likely due to a warming local climate and the effect of thermokarstic melt processes. This poses a problem to the stability of the entire glacier system, as the forelands is the only barrier shielding the glacier from warm ocean tides that come off the Gulf of Alaska. Continued degradation of this region has the potential to create a direct link between the glacier and the warmer ocean tides, potentially initiating rapid ice loss and large-scale retreat.To better understand the extent of ground ice in the forelands, transient electromagnetics (TEM) were employed to probe the subsurface and compare with imagery and geomorphology. We modeled the ground response using variable layer thickness and resistivities, in order to better distinguish what is likely ground ice from other materials. While TEM methods have previously been used to identify permafrost, it was unclear whether discontinuous deposits of ground ice would show similar resistivity profiles. Early TEM results show subsurface layers with relatively high resistivities ranging from 2,000-20,000 ohm-m in previously glaciated areas. Lower resistivities could indicate discontinuous or dirty ground ice, whereas higher values likely indicate ground ice, but whether such ice is continuous is unclear. Further modeling and the addition of seismic velocity profiles acquired at the same sites are used to help constrain the extent and thickness of ground ice in specific areas of the forelands.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/986113

2022059934 Wang, Bo (Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI); Smith, Laurence C.; Altenau, Elizabeth H.; Yang, Xiao; Pavelsky, Tamlin; Rodriguez, Ernesto and Bates, Paul D. Anabranching prevalence and intensity along the world's 20 largest rivers [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H13G-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Anabranching is a major river pattern defined as multiple channels separated by stable vegetated islands. Although it is widely observed in various environments worldwide, its prevalence has not been quantitatively studied. Disparate hypotheses for anabranching formation, including excess sediment supply, increased sediment conveyance, topographic relief, and variable flow regimes, have been developed primarily for small rivers and local scales. Here, we quantify anabranching prevalence/intensity and interpret causal factors for the world's 20 largest river basins. First, an anabranching index (Ai) is developed based on the Surface Water and Ocean Topography (SWOT) River Database (SWORD) and global surface water extents in Google Earth Engine and ArcGIS Pro. We find that ~74±16% of large-river mainstems are anabranching (defined as Ai>1 for reaches ~10 km in length), ranging from at least ~35% (Yangtze) to as much as ~96% (Ob'). With two exceptions (Yangtze and Mekong), all are anabranching for >60% of their length, including the engineered Mississippi River (~65%) due to the growth of vegetated in-channel bars. At the full-basin scale, anabranching comprises at least ~26% (Mississippi) to as much as ~69% (Ob') of all satellite-observable reaches, with a mean global value of 47±13%. Anabranching along the 20 river mainstems is most commonly associated with reduced water surface slope and abrupt floodplain widening. The appearance of unconsolidated sediments promotes anabranching with higher intensity, while permafrost increases anabranching intensity but not prevalence. The most intensely anabranching reaches are likely sediment sinks due to higher total width, suggesting reduced sediment transport efficiency. Overall, our results demonstrate that anabranching channel patterns are ubiquitous in the world's largest river systems, with implications for SWOT retrievals of river surface water extent, water surface slope, and discharge.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/891135

2022057083 Wang, Bo (Brown University, Department of Earth, Environmental and Planetary Sciences, Providence, RI); Smith, Laurence C.; Altenau, Elizabeth H.; Yang, Xiao; Pavelsky, Tamlin; Rodriguez, Ernesto and Bates, Paul D. Broad-scale controls on large river anabranching from remote sensing [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP34A-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Anabranching is one of four river channel planforms, together with straight, meandering, and braided patterns. Disparate hypotheses for anabranching formation, including excess sediment supply, increased sediment conveyance, topographic relief, and variable flow regimes, have been developed primarily for small rivers and local scales. Here, we use geospatial data analysis to quantify channel anabranching for large rivers at continental and global scales. Using an anabranching index (Ai) developed from satellite imagery, we examine empirical associations between Ai and hypothesized causal factors for the world's 20 largest river basins. We find that ~74±16% of large-river mainstems are anabranching (defined as Ai>1). Mainstem anabranching is most commonly associated with reduced water surface slope (normalized slope-1) and abrupt floodplain widening (normalized floodplain width >0.6; absolute width >15 km). Substrate lithology (i.e., unconsolidated sediments) increases both anabranching prevalence and intensity, but permafrost only increases anabranching intensity. Spatially-averaged channel width increases in the most intensely anabranching reaches relative to other reaches along the same river, suggesting net sediment storage in the anabranching reaches due to reduced transport efficiency. Overall, our results demonstrate that anabranching channel patterns are ubiquitous in the world's largest river systems, with implications for sediment budgets, river engineering, satellite discharge retrievals, and global-scale hydrodynamic models.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/890277

2022055962 Wang, Chen (Lawrence Berkeley National Laboratory, Berkeley, CA); Dafflon, Baptiste; Wielandt, Stijn; Lamb, Jack; McClure, Patrick; Uhlemann, Sebastian; Shirley, Ian and Hubbard, Susan S. Quantifying soil thermal regimes and their controls across a discontinuous permafrost environment using a dense network of distributed temperature profiling systems [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15A-1412, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In Arctic regions, the soil thermal regimes impact numerous hydrological and biogeochemical processes including soil permeability, water distribution, carbon and nitrogen cycling, and greenhouse gas emissions. While measuring soil and snow temperature time-series is essential to validate models that simulate heat, water, and carbon fluxes across the landscape, acquiring and processing data with sufficient spatial resolution to capture the heterogeneity of the system is still challenging. In this study, we investigate the plot to watershed scale heterogeneity in soil thermal regimes and their controls across a »1.5 ´ 2 km watershed near Nome, Alaska. We applied a dense network of distributed temperature profiling (DTP) systems (»120 probes in total) to measure the vertically-resolved temperature of soil and snow. Each Probe recorded the temperature at a 15 min interval over more than a year, with sensors distributed vertically with 5 or 10 cm spacing along »1 m depth. Snow thickness, soil frozen/thawed layer thickness, soil freeze/thaw durations, zero-curtain offset, thermal parameters, and other metrics were resolved from the time-series temperature data. The effects of vegetation, topography, and soil physio-chemical properties on the spatial variations of the derived parameters were investigated using laboratory analysis of soil cores and remote sensing products. The results of this study provide insights into the understanding of the thaw layer dynamics and the controls on soil thermal regimes. In particular, we found that the variability in the soil freeze-thaw timing and amplitude was strongly impacted by the snow cover dynamics and the soil water content that were both partly linked to topography and vegetation cover. The obtained information is expected to be useful for improving predictions of soil hydro-biogeochemical dynamics.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/948375

2022055960 Wang, Jian (Ohio State University, Department of Geography, Columbus, OH) and Liu, Desheng. Permafrost degradation partially explains variability of vegetation spring phenology over northern permafrost regions [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15A-1410, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Global climate change has substantially advanced vegetation spring phenology (i.e., leaf-unfolding date, LUD) over Northern permafrost regions, which is degrading due to its high sensitivity to temperature warming. Changes in LUD regulate carbon uptake of permafrost ecosystems, further feeding back to local and regional climate systems. Extant studies focused on the direct effects of climate factors (i.e., temperature, precipitation, and insolation) on LUD, however, the potential impacts of permafrost degradation on LUD have not been examined yet. In this study, we investigated the impacts of permafrost degradation on LUD over northern permafrost regions by analyzing the long-term trend of satellite-based LUD in relation to permafrost degradation measured by the start of thaw (SOT) and active layer thickness (ALT). Under warming, we found significant trends of advancing LUD, SOT, and thickening ALT (P<0.05), with a slope of -2 days decade -1, -4 days decade-1, and +1 cm decade-1, respectively. Using partial correlation analysis, more than half of the regions with significantly negative correlation between temperature and LUD became non-significant after accounting for the effects of permafrost degradation. LUD exhibits positive-dominant (38% vs 1%) and negative-dominant (2% vs 35%) responses to SOT and ALT, respectively. Permafrost degradation enhances soil water availability, thus alleviating water stress for vegetation leaf-unfolding. Permafrost degradation was the dominant factor controlling LUD variations in 42% of the regions whereas only 20% of the regions were dominated by other climatic factors. This study reveals the significant impacts of permafrost degradation on vegetation LUD and highlights the importance of permafrost status to better understand spring phenological responses to future climate change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/870655

2022055976 Wang, Jonathan (University of California Irvine, Department of Earth System Science, Irvine, CA); Baccini, Alessandro; Farina, Mary; Randerson, James Tremper and Friedl, Mark A. Disturbance suppresses the above ground carbon sink in North American boreal forests [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B22D-01, sketch map, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Climate change is altering vegetation dynamics and disturbance regimes in boreal ecosystems, which store vast amounts of carbon in its aboveground biomass and soils. However, the aggregate impact of these changes on the boreal carbon cycle is not well understood. Here we combined multiple satellite datasets, including Landsat and ICESat, with allometric equations, archival databases, and machine learning to estimate annual stocks and changes in aboveground biomass (AGB) at 30 m spatial resolution across the boreal ecoregions of western North America. Satellite-based estimates of AGB density are highly correlated (R2 = 0.69) with independent estimates of AGB from field measurements in the Northwest Territory and Alberta. From 1984 to 2014, the 2.82 ´ 106 km2 study region gained 434 ± 176 Tg AGB, but this growth has been suppressed by disturbances such as fires and timber harvest. Fires resulted in losses of 789 ± 48 Tg AGB, which were mostly compensated by post-fire recovery of 642 ± 86 Tg AGB. In contrast, timber harvests contributed to smaller losses of 74 ± 5 Tg AGB, which were partly offset by post-harvest recovery of 32 ± 9 Tg AGB. A simple bookkeeping model driven by fire areas and calibrated on post-disturbance AGB recovery curves suggests that the extent and impact of fires on regional carbon budgets has increased substantially since 1940. Earth system models overestimated AGB accumulation by a factor of 3 (+1,519 ± 171 Tg AGB), which suggests that these models overestimate the terrestrial carbon sink in boreal ecosystems and highlights the need to improve representation of fire and other disturbance processes in these models. Taken together, these datasets and analyses suggest that disturbances are increasingly reshaping the geography and magnitude of the boreal carbon cycle. There is an urgent need to characterize the extent, frequency, and carbon cycle impacts of additional boreal disturbance types, such as permafrost degradation and resource exploration, and to further improve models for quantifying carbon cycle processes using bottom-up, top-down, and empirical approaches.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/806627

2022055954 Wang, Karen Jiaxi (Brown University, Department of Earth, Environmental and Planetary Sciences, Providence, RI); Huang, Yongsong; Vachula, Richard S.; Russell, James M. and O'Donnell, Jonathan A. An annually resolved record of permafrost-thaw induced carbon cycling changes for the past 60 years from White Fish Lake, Seward Peninsula, Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B11B-02, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Recent climate change has led to widespread warming and thawing of permafrost soils across Arctic and sub-Arctic regions. Permafrost thaw alters the hydrology and biogeochemistry of terrestrial ecosystems, by releasing previously frozen organic carbon into the atmosphere as carbon dioxide and methane gases, forming a positive feedback for Earth's climate. Permafrost thaw also alters the lateral transport of carbon from terrestrial to aquatic ecosystems through thermal erosion, thermokarst, and shifting groundwater dynamics in northern catchments. However, continuous records tracking permafrost thaw and associated carbon-cycle processes in past decades are scarce. In this study, we analyzed biomarkers and bulk sediment properties from a core attained from White Fish Lake that spans the past »60 years. White Fish Lake is a crater lake located in the Seward Peninsula where the surrounding terrain is underlain by ice-rich permafrost that is susceptible to abrupt thaw. The organic-matter-rich sediment and exceptionally high sedimentation rate (1.4 cm/yr) provided opportunity for reconstructions at an annual scale. We analyzed lipid biomarkers including fatty acids, n-alkanes, diploptene, alkenones, GDGTs, as well as bulk carbon and nitrogen isotope compositions. GDGT-0, diploptene and C37 alkenone fluxes increased significantly since 2010, which suggests an increase in methanogen populations and methane production, as well as increased methane oxidizing bacteria and phytoplankton productivity. The intensified carbon cycle was also demonstrated in the bulk isotope data. The d13C content of bulk organic carbon was highly depleted (-28.87»-31.64 ppm, average of -30.21±0.59 ppm) and comparable to other thermokarst lake sediments. There is a significant decreasing trend of the d13C from 1960 to 2019 (»1.5 ppm), suggesting changes in atmospheric CO2 and increased incorporation of a methane-derived carbon source into the aquatic biomass and sediment. Our study shows that the Seward Peninsula has undergone unprecedented changes as the Arctic warms and permafrost continues to thaw.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/940373

2022059939 Wang Liuming (Nanjing University, Nanjing, China); Wang Junxiao; Zhu Liping and Li, Xingong. Terrestrial water storage regime and its response to climate change in the endorheic Tibetan Plateau [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H25H-1128, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Terrestrial water storage (TWS) and its change (TWSC) are extremely sensitive to climate change, and are good indicators of the response of hydrological system to climate change in the Tibetan Plateau (TP). Quantifying the impact of climate change on TWS regime (e.g. spatial-temporal variation, components, magnitude and duration) is essential for water resources and disaster management. In the study, we proposed a new framework to assess inter-annual and intra-annual storage regime and its alterations in the endorheic TP and its sub-regions (IB and QB) based on an extended TWS anomaly (TWSA) and TWSC of the Gravity Recovery and Climate Experiment (GRACE) (and GRACE Follow-on) from 2019 to 1989 using the random forest (RF) method. Our major findings are: (1) TWS in the IB and QB has been both increasing in most months with regional climate warming and wetting, and the higher increasing rate in the IB was mainly driven by the rapid increase of total storage in groundwater, lake, permafrost and glacier (GLPIA) in the northeastern sub-regions during post-mutation period (2005-2019); (2) Climate change altered the magnitude, variability and duration of water storage in the endorheic TP but with large temporal and spatial heterogeneity. Higher storage increase was found in the IB and its northeastern sub-regions, accompanied with a longer duration and higher variability, which may increase flood risk and threat the stability of regional hydrological system; (3) Annual TWSC in IB was mainly determined by lake water storage change (LWSC), while in QB it was mainly determined by soil water change (SWC). Intra-annual TWS change (TWSC) showed a general seasonal pattern of "early deficit-middle surplus-late deficit", which was mainly driven by soil water change in the IB and by GLPIA change in the QB, respectively, and the pattern did not change substantially in most months. The proposed framework can be used both for examining water storage regime and its alterations and thus can serve as a useful tool for understanding regional water cycle under climate change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/921096

2022056004 Ward, Rebecca (University of Bristol, Bristol, United Kingdom); Ganesan, Anita; Sweeney, Colm; Miller, John B.; Goeckede, Mathias; Laurila, Tuomas J. A.; Hatakka, Juha; Ivakhov, Viktor and Makshtas, Alexander. Quantifying Arctic methane emissions from Alaska's North Slope and northeast Siberia from 2010-2020 using high-frequency atmospheric measurements [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B43D-04, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Atmospheric methane mole fractions have been rising globally since 2007, with 2020 exhibiting the largest annual growth since intensive measurements began globally in 1983. Quantifying methane emissions from Arctic regions is crucial as temperatures have been increasing twice as fast over the Arctic as the global mean. Temperature is an important driver of methane emissions from Arctic soils, controlling rates of microbial production and permafrost thaw. We use a range of methods to quantify emissions and assess trends from the North Slope of Alaska and Northeast Siberia using the most recent data from near-coastal Arctic surface sites. Methods include: the analysis of trends in methane mole fraction enhancements over background from the land sector and as the quantification of emissions at monthly resolution through Bayesian inversions using the NAME atmospheric transport model. This study employs data from the surface sites at Barrow, Alaska and Ambarchik, Tiksi and Cape Baranova, Russia. Preliminary analyses at Barrow using data up to 2020 show that emissions from Alaska's North Slope have increased substantially in recent years, reflecting a change from previous analyses, which showed no significant increase in summertime methane emissions between 1986-2014. (Sweeney et al., 2016). We show that methane enhancements over background from the land sector increased most prominently from July to September, and that late Autumn enhancements continue to rise at a rate similar to the previous decades. We also find substantial terrestrial emissions from Northeast Siberia occurring both in the Summer as well as in the Autumn months, suggesting important "zero-curtain" emissions. We investigate correlations between surface air temperature and surface inundation with methane enhancements to determine the likely drivers of these enhanced emissions. Our findings can be used to assess whether important changes to the Arctic cryosphere are beginning to be observed.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/838380

2022055996 Watts, Jennifer (Woodwell Climate Research Center, Falmouth, MA); Natali, Susan; Minions, Christina and Czimczik, Claudia I. Investigating regional patterns of soil respiration in Alaska and Canada [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31E-03, sketch map, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Soil respiration provides one of the largest global fluxes of carbon dioxide (CO2) to the atmosphere and is likely to increase with warming. However, the magnitude of soil respiration loss from thawing Arctic-boreal regions is not well understood. To address this important knowledge gap, we compiled a new CO2 flux database for permafrost-affected tundra and boreal ecosystems in Alaska and Northwest Canada. We used the CO2 database, satellite imagery, and Random Forest models to assess regional magnitudes of soil respiration, on a seasonal-to-annual basis. The flux database includes a new Soil Respiration Station network of chamber-based fluxes, and fluxes from eddy covariance towers. Our site-level data, spanning September 2016 to August 2017, showed the largest soil respiration emissions during summer (June-August); summer fluxes were higher in boreal sites relative to tundra. Considerable winter (November-March) emissions (boreal: 0.24 + 0.2 gCO2-C m-2 d-1; tundra: 0.18 + 0.16 gCO2-C m-2 d-1) were observed, even when surface temperatures were well below 0°C. Our model estimates indicated an annual region-wide loss from soil respiration of 591 + 120 Tg CO2-C during the 2016-2017 period. In total, soil respiration offset 54% of annual gross primary productivity (GPP) across the study domain. However, we found that in tundra environments, transitional tundra/boreal ecotones, and in landscapes recently affected by fire, soil respiration often exceeded GPP, resulting in a net annual source of CO2 to the atmosphere. When accounting for soil + aboveground respiration, total ecosystem respiration (ranging from 820-1171 Tg CO2-C) for the domain offset 74-106% of annual total regional GPP. Our assessment indicates an urgent need to support and expand carbon flux monitoring networks across the permafrost domain, especially as regional temperatures continue to exceed previous records of warming. Ongoing project research will also investigate, through radiocarbon 14C analysis, how belowground root vs microbial respiration components contribute to seasonal changes in total observed soil CO2 flux.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/903369

2022055997 Webb, Elizabeth (University of Florida, Ft. Walton Beach, FL); Liljedahl, Anna; Loranty, Michael M.; Cordeiro, Jada A. and Lichstein, Jeremy W. Permafrost thaw drives surface water drainage across the pan-Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31E-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Lakes constitute 20-40% of Arctic lowlands, the largest area fraction occupied by water bodies in any terrestrial biome. These lakes provide crucial habitat for fish and migrating bird species, support human subsistence fisheries, and provide a source of water for remote Arctic communities. Recent evidence suggests that climate change could be shifting these dynamic systems across an ecological threshold, towards long-term landscape-scale wetting (lake formation) or drying (lake drainage). The spatial variability of and mechanisms underlying these shifts, however, are not well understood. Here we use MODIS imagery to map trends in July surface water across the circumpolar region over the past 21 years (2000-2021). We then relate these surface water trends to factors expected to contribute to wetting or drying trends, such as changes in air temperature, precipitation, and evaporation. Our results reveal large-scale drying across the pan-Arctic, a trend that is correlated with increases in winter temperature and fall rain. Given that increasing winter temperatures and fall rain are known to promote permafrost thaw, our results suggest that permafrost thaw is leading to lake drainage and increasing surface water infiltration across the region.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/817165

2022055950 Wilson, Emily Lynn (NASA, Goddard Space Flight Center, Greenbelt, MD); Ramu, Guruthisvaran; Hacker, Steven; Villanueva, Geronimo; Palmer, Paul I.; Levy, Gideon; Shu, Jiefan and Boelen, Siti. Status of testing, and calibration of the miniaturized Laser Heterodyne Radiometer (mini-LHR), and a timeline for deploying a global round network of CH4 and CO2 sensors [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract A54C-06, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Our team at NASA Goddard Space Flight Center has invested over a decade in developing the mini-LHR - an inexpensive ground instrument that measures carbon dioxide (CO2) and methane (CH4) in the atmospheric column with precisions of better than 1 ppm XCO2 and 20 ppb XCH4 for hourly data products and a resolving power of greater than 500,000. The mini-LHR is autonomous (after initial set-up), operates exclusively on solar power, and fits neatly in a backpack for easy deployment to remote areas with no power grid. The underlying technology in the mini-LHR is similar to that in an FM radio and is essentially a superheterodyne with a commercial distributive feedback (DFB) laser used as the local oscillator. The mini-LHR is not a LIDAR but rather a passive instrument because laser light never leaves the instrument. Sunlight in the infrared (1.6 microns) is collected and mixed with laser light to produce a beat signal and a direct absorption signal is recorded as the laser scans across CO2 and CH4 absorption features. Scans are processed into half or full hour data products and finally analyzed with a retrieval algorithm that is publicly available through Goddard's Planetary Spectrum Generator (PSG). The mini-LHR has been tested extensively in the field with some notable locations including Mauna Loa Observatory (MLO), Hawai'i Space Exploration Analog and Simulation (Hi-SEAS), The Bonanza Creek Research Forest (sites with thawing permafrost), and two Total Carbon Column Observing Network (TCCON) sites for validation. Future potential deployment locations include wetlands, thawing permafrost, the tropics, the Amazon, sub-Saharan Africa. In 2019, we evaluated the impact of a proposed network of mini-LHRs through Observing System Simulation Experiments (OSSEs) and found that for a network with 50 strategically placed mini-LHRs, the potential improvement (which varies seasonally) ranged from 58-81 percent over southern lands, 47-76 percent over tropical lands, 71-92 percent over northern lands, and 64-91 percent globally. While the impact of this global network would be significant, and the price tag small (parts cost »$10K per instrument), funding for the final long-term validation test to make this network a reality has not been available. In spite of this obstacle, we have licensed the patent to MACH 33 Engineering, LLC in Laurel, Maryland and they are working with a non-profit in the Netherlands and plans are underway to manufacture this instrument and make it commercially available.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/809615

2022055969 Windholz, Tiffany (Oklahoma State University, Stillwater, OK); Virkkala, Anna-Maria; Rogers, Brendan M.; Fiske, Greg and Natali, Susan. Analyzing terrestrial carbon flux site distribution across the Arctic [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15C-1440, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic tundra and boreal biomes store large amounts of carbon that have the potential to undergo change as the Arctic is warming two to three times faster than the global average. Understanding carbon fluxes across the tundra and boreal biomes is therefore crucial to understanding how the Arctic is both responding and contributing to climate change. However, many articles have highlighted the lack of carbon flux data needed to fully comprehend the current state of the Arctic carbon balance. Over the past few decades, a growing network of terrestrial ecosystem CO2 flux sites has been established across the Arctic. However, it is not well known how well these sites cover the different climate, permafrost, and soil organic carbon conditions. We used an existing flux database and gridded datasets to explore and visualize the distribution of sites. Some regions of the Arctic, including Alaska, south-central Canada, and northern Europe, are well represented by the current sites. In contrast, regions such as northern and eastern Canada, which have high precipitation and carbon-rich conditions, and much of Russia, which has both some of the coldest and warmest mean temperatures across the Arctic, remain under-sampled and not well represented. The lack of data from these areas suggests that the scientific community has a major knowledge gap, hindering our ability to understand and predict the current or future carbon balance of these ecosystems. We highlight particular areas where new site installation would substantially increase representativeness, including eastern Canada, southern Norway, and most of Siberia.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/954698

2022057058 Witharana, Chandi (University of Connecticut, Department of Natural Resources and the Environment, Groton, CT); Udawalpola, Mahendra; Hasan, Amit and Liljedahl, Anna K. High performance image analysis workflow designs for operational-scale Arctic permafrost mapping applications [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Commercial satellite imagery can capture dynamics of individual microtopographic features, such as ice-wedge polygons, individual trough or water tracks without sacrificing the geographical extent. Data processing challenges combined with growing quest for pan-Arctic scale permafrost modelling efforts spontaneously set the stage for state-of-the-art artificial intelligence (AI) algorithms, such as deep learning (DL) convolution neural nets (CNNs). Despite the remarkable performances of DLCNNs in everyday image understanding, bottlenecks still exist when translated to geo-object detection from remote sensing imagery. Image dimensions, multiple spectral channels, spatial reference, seasonality, and most importantly semantic complexity aggregated into multiple spatial scales pose greater friction on the inferential strengths of DLCNN model predictions. Scalability of automated analysis over millions of square kilometers comprising heterogeneous landscapes reverberates the need for efficient image-to-assessment workflows that center on high performance computing resources (HPC). We have developed a novel high performance image analysis framework - Mapping application for Arctic Permafrost Land Environment (MAPLE) - that enables the integration of operational-scale GeoAI capabilities into Arctic science applications. The MAPLE workflow is three-fold: image preprocessing, DLCNN prediction, and post-processing. While the first and last segments involve CPU implementations, the prediction operates on GPUs. In this study, we have investigated highly-parallelized four workflow designs to implement MAPLE on heterogeneous HPC systems. It is equally important to understand how different workflow designs interact with underlying service unit (SU) accounting models of HPC systems. We systematically analyzed the execution time of image-pre processing, DLCNN model execution, geospatial data generation of each design when predicting ice-wedge polygons and water bodies from satellite imagery. Currently, the MAPLE combines DLCNN algorithms with heterogenous HPC resources to automatically identify ice-wedge polygons from thousands of commercial satellite imagery at an unprecedented spatial scale and also to detect small scale water bodies in the Arctic permafrost tundra.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/966523

2022055999 Wu, Yue (University of Texas at Austin, Department of Aerospace Engineering & Engineering Mechanics, Austin, TX); Chen, Jingyi; O'Connor, Michael; Ferencz, Stephen Bruce; Cardenas, M. Bayani and Kling, George W. The uncertainty in InSAR-based active layer soil water storage estimates over the Arctic foothills [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B31E-07, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Recent studies show that groundwater flow through the topmost portion of permafrost soil, known as the active layer, has a significant contribution to the export of carbon in permafrost terrain. Because the Arctic covers continent-sized areas that are mostly inaccessible, remote-sensing has become a critical tool for observing continuous permafrost. Particularly, the density difference between liquid water and ice causes seasonal ground surface deformation that can be detected over large spatial scales using Interferometric Synthetic Aperture Radar (InSAR). Here, we analyzed L-band ALOS PALSAR scenes acquired between June and October from 2006 to 2010 (Path 255, Frame 1370-1380) near Toolik Lake and solved for the seasonal thaw subsidence and frost heave associated with the active layer freeze-thaw cycle. We confirmed that the maximum thaw subsidence is proportional to the total soil water content in the active layer using in-situ measurements of the hydraulic properties and stratigraphies at over 200 sites across the Arctic Foothills. We found that the average seasonal thaw subsidence increases along a geomorphic-ecohydrologic transect starting with heath vegetation on the drier ridge-tops, transitioning into tussock tundra on hillslopes, and draining into lowland riparian zones with wet sedge tundra. We also quantified the uncertainty in the InSAR measurements. We found that the misregistration between the Arctic DEM and a subset of SAR images leads to a DEM error in InSAR phase measurements. This is the dominant error source in the ALOS Toolik InSAR data, particularly in areas with large slope angles (> 7.5%). We developed a mitigation strategy, that reduces the uncertainty in the InSAR-based soil water estimates from > 20 cm to < 10 cm. Our study suggests that InSAR has greater observational capabilities than previously assumed for monitoring changes in hydrological and ecological characteristics above continuous permafrost and estimating large-scale soil moisture.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/862240

2022057056 Yanagiya, Kazuki (Hokkaido University, Sapporo, Japan); Furuya, Masato; Iwahana, Go and Danilov, Petr. High-resolution frost heave map at the fire scars in Batagay, NE Siberia, derived by L-band InSAR and validation with field observation [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C52A-06, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Wildfire causes abrupt thaw of near-surface permafrost due to the loss of surficial vegetation layer. The number of fires and burned areas are increasing in the Arctic region due to global warming and will further accelerate permafrost degradation, especially in ice-rich permafrost regions. However, it remains uncertain how much wildfires could increase the abrupt thaw. Also, the abrupt thaw has not been considered in the previous estimations of carbon release from permafrost. To widely observe abrupt thaw process immediately after wildfire, we study two fire scars formed in 2018 and 2019 in Batagay village, the Sakha Republic, Northeastern Siberia. The two fire scares are located adjacent to the Batagaika mega-slump, located 12 km southeast of the village. By monitoring topography change immediately after the fires with a remote sensing technique, we can evaluate the amount of abrupt thawed permafrost. We use Interferometric Synthetic Aperture Radar (InSAR), a remote sensing technique that allows us to detect relative ground deformation between an imaging period. Yanagiya and Furuya (2020) revealed spatio-temporal variation of post-fire permafrost thawing by InSAR at the 2014 fire scar near Batagay. This study derives the higher-resolution map by ALOS2 L-band SAR satellite data and the 2-meter data of ArcticDEM over the 2018 and 2019 fire scars. The spatial resolution of the deformation map is 4-meter. The deformation map revealed that seasonal frost heave has spatially close correspondence to gullies at the scars. The InSAR image indicates spatially uniform heave of up to 10 cm over flat areas in the fire scars. In contrast, heave signals are spatially heterogenous at the gullies. Heave occurs especially in the bottom of the gullies, but almost no heave in the flanks. We interpret the spatial variation corresponding to the gullies due to spatial differences in the amount of ice lens formation caused by soil moisture content distribution. Besides, we will further discuss the one-year thaw subsidence maps and the validation with the field data that will be taken in September 2021.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/879334

2022055985 Yang, Daryl (Brookhaven National Laboratory, Department of Environmental and Climate Sciences, Holbrook, NY); Morrison, Bailey Danielle and Serbin, Shawn. Integrating field observations and multi-scale remote sensing to understand tall shrub distribution and environmental limits in Arctic tundra [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B24D-03, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic region has experienced some of the most rapid climate warming on Earth. In response to this warming and associated permafrost thaw, the abundance of tall shrubs (those that can potentially grow >2 m) has been observed increasing across the Arctic, causing substantial and complex impacts on biodiversity, energy balance, and the biogeochemical cycling of carbon, water, and nutrients. However, large uncertainties persist in addressing the critical question: what drives the patterns and rate of shrub expansion in Arctic tundra? Warming temperatures and permafrost thaw have been linked to the increased shrub cover in the Arctic. However, shrub distribution is also likely limited by other biotic and abiotic factors that do not favor their growth, and changes in these limiting factors could have larger or more direct impacts on shrub expansion. In this study, we combined ground observations and multi-scale remote sensing data (UAS, NASA ABoVE AVIRIS-NG, ArcticDEM, and high-resolution climate data) to investigate the environmental limiting factors (ELFs) of two tall shrub genera (alder and willow) in the Seward Peninsula, Western Alaska. We first developed a partial least squares regression (PLSR) model to predict the fractional cover (FCover) of alder and willow from AVIRIS-NG imagery by integrating UAS and AVIRIS-NG data. Using the developed PLSR model, we mapped the FCover of alder and willow across multiple AVIRIS-NG flights collected across the Seward Peninsula. We then combined these FCover maps with topographic, climate, and soil moisture data to construct ELF models for alder and willow, respectively, and mapped the EFL of alder and willow across the Seward Peninsula. Our results show that the distribution of alder and willow are driven by different environmental variables, where the distribution of alder is strongly affected by topography and energy related factors (e.g., radiation and temperature), while the distribution of willow is strongly tied to water related factors (e.g., topographic wetness and soil moisture). In addition, willow species can extend to more extreme environments than alder. These results suggests that continued climate warming in the Arctic may affect the expansion of alder and willow differently, which lead to distinct distribution patterns of the two genera.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/987827

2022057001 Yang Yuanhe (Chinese Academy of Sciences, IB Institute of Botany, Beijing, China); Qin Shuqi; Kou Dan; Mao Chao; Chen Yongliang and Chen Leiyi. Temperature sensitivity of permafrost carbon release mediated by mineral and microbial properties [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45K-1764, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Temperature sensitivity (Q10) of permafrost carbon (C) release upon thaw is a vital parameter for projecting permafrost C dynamics under climate warming. However, it remains unclear how mineral protection interacts with microbial properties and intrinsic recalcitrance to affect permafrost C fate. Here, we sampled permafrost soils across a 1000 km transect on the Tibetan Plateau and conducted two laboratory incubations over 400-day and 28-day durations to explore patterns and drivers of permafrost C release and its temperature response after thaw. We find that mineral protection and microbial properties are two types of crucial predictors of permafrost C dynamics upon thaw. Both high C release and Q10 are associated with weak organo-mineral associations but high microbial abundances and activities, whereas high microbial diversity corresponds to low Q10. The attenuating effects of mineral protection and the dual roles of microbial properties would make the permafrost C-climate feedback more complex than previously thought.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/806784

2022059936 Yi Yonghong (Tongji University, College of Surveying and Geo-Informatics, Shanghai, China); Chen, Richard H.; Kimball, John; Moghaddam, Mahta; Xu, Xiaolan; Euskirchen, Eugenie Susanne; Das, Narendra N.; Miller, Charles E. and Park, Chang-Hwan. Potential satellite monitoring of surface organic soil properties in Arctic tundra from SMAP [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H15W-1316, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Surface soil organic matter (SOM) and soil moisture represent first-order controls on permafrost thaw and vulnerability, yet remain challenging to map or model accurately. In this study, we explored the links between surface organic soil properties and soil moisture dynamics in the Alaska North Slope through data analysis and process-based modeling. Our analysis, based on in-situ soil moisture and brightness temperature data from the Soil Moisture Active Passive (SMAP) mission, indicated that the soil moisture drydown process in tundra is closely related to surface organic carbon (SOC) content. More rapid dry-down was generally observed in areas with high SOM concentration. The drydown time scale derived from the L-band polarization ratio (PR) was significantly correlated with SoilGrids surface (0-5 cm) SOC concentration (R=-0.54 ~-0.68, p<0.01) at regional scale. To understand the process, we used a coupled permafrost hydrology and microwave emission model to simulate changes in soil moisture and L-band PR during the thaw season. Soil parameters and dielectric models adapted for tundra were also included to better describe the variations in soil hydraulic and dielectric properties with SOM. The hydrology model was calibrated and validated using in-situ evapotranspiration, soil moisture and temperature measurements from Imnavait Creek, Alaska. The hydrology model was coupled with the widely used tau-omega model to investigate PR sensitivity to surface soil carbon properties. Model sensitivity runs showed larger L-band PR decreases during the early thaw season in soils with higher SOC concentration consistent with the above analysis; whereby, highly organic soils (SOM>60%) drain water more easily with a larger amount of water discharged or lost (through evapotranspiration) relative to soils with less carbon content (SOM<30%). However, the PR sensitivity to SOM was reduced with increasing vegetation water content and surface roughness, such as during the later thaw season. We find that the satellite L-band observations are sensitive to tundra soil moisture and carbon properties, and may provide critical constraints on predictions of permafrost thaw and vulnerability in the Arctic.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/846018

2022055981 Yoseph, Elizabeth (Bard College, Annandale-on-Hudson, NY); Hoy, Elizabeth; Elder, Clayton; Thompson, David R.; Miller, Charles E. and Chatterjee, Abhishek. Arctic tundra fires promote greater methane hotspot occurrence in the Yukon-Kuskokwim Delta, Alaska, USA [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B23C-02, illus., December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The Arctic has experienced dramatic climate-induced changes that have significant implications for current and future global climate change. However, some of the specific drivers and dynamics in this region remain poorly understood. Our study extends research initially presented at the AGU 2020 Fall Meeting using enhanced fire perimeter to ensure the validity of preliminary results. Last year, we provided process-level and local scale analyses that revealed fire disturbance as a potential driver of methane emission hotspots in one of the more active tundra fire regimes in Alaska, the Yukon-Kuskokwim (Y-K) Delta. We leveraged a new airborne dataset developed by Elder et al. (2020) of high-resolution spectroscopy (AVIRIS-NG) that revealed spatial distribution patterns of CH4 hotspots across the entire Arctic-Boreal Vulnerability Experiment (ABoVE) domain. Hotspots for the Y-K Delta subset of the AVIRIS-NG dataset were analyzed in conjunction with geospatial data layers (i.e., Alaska fire history). Preliminary results included, but not limited to, that burned areas consistently had a higher ratio of hotspots than in unburned areas across all flight lines, implying that tundra fire promotes sites of intense CH4 emissions (Figure 1). Our preliminary results suggested that the projected increases in fire frequency and severity associated with enhanced CH4 emissions could enhance the permafrost carbon feedback, and thus accelerate climate warming.We now provide further investigation into this relationship using a more precise estimate of burned area to ensure our results are robust. Our extended analysis uses enhanced fire measurements by merging data from the Alaska Fire Large Database with Mapping Trends in Burn Severity products to derive a new dataset using the best available data. In addition, we apply a sun glint correction for all flight lines to ensure consistency. Finally, we analyze reflectance surface spectra to disprove potential biases arising from substrate differences in burned versus unburned areas. Our extended analysis shows that the influence of fire disturbance on the distribution of CH4 hotspots is consistent with our preliminary results, therefore, demonstrating a strong level of confidence in the fire-carbon relationship presented last year.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/1002391

2022059959 Young, Mackenzie (University of Alaska Fairbanks, Fairbanks, AK); Mann, Daniel H.; Gaglioti, Benjamin; Darrow, Margaret M. and Larsen, Christopher F. A dendro-geomorphological analysis of the Slate Creek landslide, Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NH35E-0502, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Mass movements are some of the main ways that hillslopes re-equilibrate to a new climatic regime. The impacts of climate change on mass movements are predicted to be especially pronounced at high latitudes where temperatures are warming most rapidly, and precipitation is increasing at higher rates than at lower latitudes. Because of its instability once thawing occurs, the presence of perennially frozen ground (permafrost) further increases the probability that mass movements will increase significantly in high latitude landscapes over the next few decades. With these predictions in mind, it is likely that critical infrastructure in Interior Alaska will be increasingly threatened by mass movements over the next few decades. We sought to understand the dynamics of the Slate Creek Landslide that is currently encroaching on the Parks Highway at Mile 258 along the northern front of the Alaska Range. To accomplish this, we use the dendrochronology of leaning and split trees growing on the landslide surface, time series of landslide movement based on repeat aerial photography and LIDAR imagery, and differential GPS measurements of landslide movement at monthly to biennial time scales. Results show that different parts of this landslide have moved at and continue to move at rates ranging from 0.2 cm up to 7 m/year. Repeat LiDAR imagery also suggests that the head-scarp of the landslide has retreated 50 m since 2011. Based on these data and the number of tree samples (n=122), the mid-1970s to early 1980s was a period of enhanced landslide movement. We tentatively correlate the increased movement of the Slate Creek Landslide with the increase in precipitation and abrupt shift to warmer air temperatures that accompanied the regime shift in the Pacific Decadal Oscillation in the mid-1970s.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/820653

2022059967 Zapata, Mauricio de Jesús Arboleda, Sr. (University of Potsdam, Institut für Geowissenschaften, Potsdam, Germany); Angelopolous, Michael; Overduin, Paul; Grosse, Guido; Jones, Benjamin M. and Tronicke, Jens. Using a layer-based model parameterization to globally invert 2D electrical resistivity data from submarine permafrost environments [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract NS15A-0360, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

In shallow coastal regions of the Arctic with newly submerged permafrost, the submarine subsurface is usually characterized (in the summer season) by a two-layer environment consisting of unfrozen sediments (talik) overlying frozen sediments. Because we usually expect a high resistivity contrast between these layers, electrical resistivity tomography (ERT) is a typical geophysical method to explore the depth of this contact, also known as the ice-bearing permafrost table (IBPT). Typically, deterministic inversion routines are used to obtain a smooth resistivity model from measured values and to interpret the IBPT position. This approach may be appropriate when prior information suggests gradual subsurface resistivity variations. However, a layer-based model parameterization (LBMP) is preferred when prior information suggests a sharp interface between talik and permafrost. Additionally, the number of model parameters in a LBMP strategy is limited, making this approach attractive for global inversion methods. To demonstrate the advantages of using a LBMP, we use the particle swarm optimization algorithm to obtain an ensemble of inverted resistivity models of two ERT data sets collected offshore of the Bykovsky Peninsula, Siberia, and Drew Point, Alaska. Although these data sets were acquired with different electrode configurations and under different environmental conditions (e.g., seawater layer with different depths and resistivities), our results show that our LBMP global inversion strategy is successful in inferring the depth of the IBPT including uncertainties. Furthermore, our approach allows investigating the relevance of prior information (e.g., water depth and resistivity) and the limits of specific electrode configurations. Therefore, it can also be considered as a feasible tool to plan and design future field experiments.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/812715

2022057096 Zhang, Ting (National University of Singapore, Singapore); Li, Dongfeng; Kettner, Albert and Lu, Xi Xi. Reproducing dynamic sediment-discharge relationships driven by time-varying sediment availability in cold basins; the sediment-availability-transport model [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract EP55C-1123, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Ongoing climate warming has significantly accelerated glacier-snow-permafrost melting and expanded the erodible landscapes in cold environments. The subsequently amplified sediment availability leads to the highly time-varying suspended sediment concentration (SSC) and discharge (Q) relationships. However, the sediment rating curve (SSC=a´Qb with a and b as fitting parameters) fails to capture the dynamic SSC-Q relationships and the widespread SSC-Q hysteretic patterns. To bridge this gap, we propose a Sediment-Availability-Transport (SAT) model to simulate the long-term evolution and dynamics in suspended sediment transport by integrating the sediment availability coupled by thermal processes, fluvial processes and long-term storage exhaustion into traditional rating curves. In the SAT-model, increased sediment sources from glacier-snow-permafrost erosion are represented by changes in the basin temperature, showing an exponential amplification of SSC when basin temperature increases and thermally-controlled sediment sources are activated. These thermal processes are found to be best captured by the eight-day average temperature (with one-week antecedent conditions). Enhanced fluvial erosion by the elevated water supply from rainfall and meltwater is represented by an intensification of runoff, which results in a linear amplification of SSC when runoff surge strengthens and erosion processes are enhanced by flushing and channel scouring. Such fluvial processes are found to be best captured by the two-day discharge increase. With the support of multi-decadal daily SSC and Q in-situ observations (1985-2017), the SAT-model can be validated for the permafrost-dominated Tuotuohe basin on Tibetan Plateau. Results show that sediment rating curves for Tuotuohe display significant inter-annual variations. The higher parameter-b in a warming and wetting climate confirms the increased sediment availability due to the expanded erodible landscapes and gullying-enhanced connectivity between channels and slopes. Through capturing such time-varying sediment availability, the SAT-model can robustly reproduce the long-term evolution, seasonality, and various event-scale hysteresis of SSC, including clockwise, counter-clockwise, figure-eight, counter-figure-eight, and more complex hysteresis loops. Overall, the SAT-model can explain over 75% of long-term SSC variance, outperforming the sediment rating curve approach by 20%. The performance of the SAT-model is stable, even under an abrupt hydroclimate change, with a Nash-Sutcliffe efficiency coefficient ranging from 0.76 to 0.71 during the calibration and verification periods respectively. The SAT-model not only advances understanding of sediment transport mechanisms coupled by thermal/fluvial erosion processes, but also provides a ready-to-use model to simulate and project future sediment loads for other cold basins.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/796473

2022056001 Zhao, Yuhuan (University of Southern California, Department of Electrical and Computer Engineering, Los Angeles, CA); Chen, Richard H.; Whitcomb, Jane; Dogaheh, Kazem Bakian; Yi, Yonghong; Kimball, John and Moghaddam, Mahta. Forest classification using airborne SAR and lidar data in interior Alaska [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B32B-05, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Forest type classification using remote sensing plays an important role in monitoring forest growth, retrieving subsurface properties, and exploring the dynamics of boreal forest ecosystems. The distribution of forest types in interior Alaska is influenced by soil and microclimate variability driven by topography, permafrost conditions, and disturbance history. The general forest types can be characterized by six dominant species: white spruce, balsam poplar, black spruce, tamarack, paper birch and quaking aspen. The associated classification information is useful in quantifying subsurface parameters, such as active layer thickness (ALT) and soil moisture. White spruce, aspen, paper birch and balsam poplar are generally found in locations with well-drained soils and deep ALT, while black spruce and tamarack occupy colder permafrost soils with shallow ALT.In order to map forest types over large areas, we propose a random forest (RF) framework to train a classification model using synergistic remote sensing retrievals from Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) and LiDAR. We exploit L-band UAVSAR observations acquired during NASA ABoVE airborne campaigns in 2017, along with NASA G-LiHT data, and combine them with in-situ forest data provided by US Forest Inventory and Analysis (FIA) and Cooperative Alaska Forest Inventory (CFAI). The classification model relates the SAR and G-LiHT derived metrics to specific forest types indicated from FIA. Boreal forests sites in Delta Junction, Bonanza Creek and Denali, Alaska are investigated since large amounts of in-situ data have been collected within these areas. Training data for the model are obtained by bootstrap sampling in-situ data available in the SAR swaths, which helps to capture ample information for different locations. The remaining in-situ data are used for evaluation of classification accuracy. For interpretation and improvement of the classification model, we also study the significance of different variables as input features, including burn history and soil texture. The resulting well-trained classification model is employed to generate a 30 m resolution forest classification map for interior Alaska, which provides enhanced accuracy to inform studies on how boreal forests are responding to climate change.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/996507

2022055961 Zhou, Wenbo (University of Michigan Ann Arbor, Ann Arbor, MI); Ivanov, Valeriy Y.; Sheshukov, Aleksey Y.; Wang, Jingfeng and Liu, Desheng. Permafrost fate in northwestern Siberia under projected climate change during 21st century [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15A-1411, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

The ongoing process of permafrost thaw in the northern circumpolar regions will potentially affect ecosystem, infrastructure, and indigenous communities in the Arctic and can also amplify the global climate through positive feedbacks mechanisms. However, observations have shown different warming rates across the Arctic. For example, based on decadal borehole measurements between 2007 and 2016 one of the fastest warming rates is in the Northwestern Siberia as compared to other Arctic regions with continuous permafrost. With predicted continued warming of climate, it is important to understand the degree of permafrost degradation in the future. In this study, we assess permafrost thaw using a one-dimensional subsurface thermal model. We first calibrate the model by using borehole measurements from the Global Terrestrial Network for Permafrost (GTN-P) and the Circumpolar Active Layer Monitoring (CALM) program. We then compute ground heat fluxes using a soil heat flux model forced with soil temperature outputs obtained from general circulation models (GCM) of the Coupled Model Intercomparison Project Phase 6 (CMIP6). The computed ground heat fluxes are constrained using uncertainty quantification method. In order to correct GCM model biases, a downscaling method based on Bayesian averaging is applied. Different future climate scenarios (e.g., ssp245, ssp585) are considered in the prediction. Our study demonstrates an effective method to simulate permafrost degradation at regional scales and provides insights on the likely changes of subsurface thermal-moisture regimes in the Northwestern Siberia under warming climate.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/985925

2022055958 Zhu, Modi (Georgia Institute of Technology, Atlanta, GA); Wang, Jingfeng; Ivanov, Valeriy Y. and Sheshukov, Aleksey Y. A physically based analytical model of permafrost active layer thawing depth [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B15A-1407, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

A physically based analytical model is formulated for simulating the thawing depth of permafrost active layer under changing surface boundary conditions at sub-daily scale. The conservation of energy for the thawing active layer leads to a nonlinear integral equation of thawing depth driven by time-varying ground heat flux. Soil temperature profile of the thawing layer is represented by an approximate analytical solution of heat conduction. Ice content profile was derived from the difference between pre- and post-freezing soil liquid water content. Ground heat flux as the energy supply of thawing is modeled using two non-gradient models from net radiation and/or surface temperature. The model was validated against field observations at Arctic forest and tundra sites. The simulated thawing depth and soil temperature are in good agreement with the field observations.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/817275

2022057003 Zolkos, Scott (American Geophysical Union); Natali, Susan; Balcom, Prentiss; Rogers, Brendan M.; Ludwig, Sarah; Minions, Christina; Kholodov, Alexander L.; Spawn, Seth; Baillargeon, Natalie; MacArthur, Rhys; Bröder, Lisa and Sunderland, Elsie M. Permafrost mercury sources and implications for methylation among Alaskan ecoregions [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract B45N-1798, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Over millennia, permafrost aggradation at northern high latitudes has sequestered large amounts of mercury (Hg) bound to soil organic matter. As intensifying permafrost thaw releases substrate into modern biogeochemical cycles, previously sequestered Hg may be susceptible to microbial methylation into methylmercury (MeHg), a potent and bioaccumulative neurotoxicant of significant concern in northern ecosystems. But, the sources and distribution of Hg across permafrost landscapes--and thus implications for methylation--are likely to be influenced by variation in geology, climate, and ecosystem history. To better understand how variation in permafrost landscape history may drive the response of Hg cycling to thaw, we investigated Hg sources (using Hg stable isotopes), lability (experimental assays), MeHg content, and organic matter composition (pyrolysis-gas chromatography-mass spectrometry, 14C) within permafrost cores collected from across Alaska. Due to broad potential influence from glaciation on permafrost sediment composition (e.g., organic versus mineral) and Hg cycling (e.g., atmospheric versus geogenic sources), we hypothesized that Hg sources, lability, and MeHg content would differ more strongly across gradients of glaciation than between ecoregions with similar glacial histories. We hypothesized that permafrost in glaciated terrains would contain a greater proportion of geogenic Hg (from regional shale lithologies) that would have lower lability and MeHg content, reflective of recalcitrant organic matter, less nutrient availability, and a cryotic state that has suppressed methylation for millennia. Among unglaciated terrains, we hypothesized that organic matter composition and Hg sources would vary by depositional environment (e.g., peat, loess) and MeHg content would broadly correlate with biolability. Preliminary results indicate that MeHg content was relatively low (0.4-0.9 ng g-1) and not primarily associated with glacial history. We consider results within the context of landscape evolution during the past ~10 kyr to help conceptualize future potential trajectories of northern Hg cycling and implications for methylation throughout northern permafrost environments.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/973593

2022059953 Zussman, Tal (Columbia University of New York, Department of Computer Science, New York, NY); Schwenk, Jon and Rowland, Joel C. River and basin profiler; a module for extracting watershed boundaries, river centerlines, and catchment statistics [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract H54G-08, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

Watersheds serve as natural spatial boundaries whose characteristics are often indicators of the hydrologic processes within them. Watershed characteristics are frequently used as predictors, parameters, or proxies in models of hydrologic and ecologic dynamics. Developments in DEMs over the past decade have resulted in elevation data spanning the globe that allows watershed delineation at arbitrary locations. In tandem, satellite-based observations and large-scale modeling efforts provide many sources of near-global watershed characteristics, e.g. topography, soil types, vegetation, climate, permafrost extent, and many more. However, with growing data availability comes a growing need for tools that can rapidly query and summarize them. We developed River and Basin Profiler (RaBPro), a Python module providing a pipeline to delineate drainage basins for any point on Earth and calculate watershed statistics for practically any geospatial raster dataset. RaBPro makes use of the MERIT-Hydro or HydroBASINS datasets to define watershed polygons, which can be exported in GeoJSON or ESRI shapefile format for further use in GIS software. RaBPro will also generate streamlines and river elevation profiles. Finally, RaBPro calculates statistics over delineated basins using Google Earth Engine (GEE). By taking advantage of GEE's vast dataset archive and distributed computing system, RaBPro can quickly compute many statistics over even very large basins efficiently and without the need for storing large geo-rasters locally. Additionally, users may upload their own datasets to GEE and create custom statistic functions.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/992836

2022057033 Zwieback, Simon (University of Alaska Fairbanks, Department of Geosciences, Fairbanks, AK); Boike, Julia; Chadburn, Sarah; Martin, Julia; Althuizen, Inge; Anselm, Norbert; Cai Lei; Coulombe, Stéphanie; Lee, Hanna; Liljedahl, Anna K.; Schneebeli, Martin; Sjoberg, Ylva; Smith, Noah; Smith, Sharon L.; Streletskiy, Dmitry A.; Stünzi, Simone Maria; Westermann, Sebastian and Wilcox, Evan. A user-friendly, multi-parameter protocol for monitoring permafrost thaw [abstr.]: in AGU 2021 fall meeting, American Geophysical Union Fall Meeting, 2021, Abstract C35F-0933, December 2021. Meeting: American Geophysical Union 2021 fall meeting, Dec. 13-17, 2021, New Orleans, LA.

There is an urgent need for standardized data collection to better understand permafrost thaw and its interaction with vegetation, hydrology, soil and snow. To enable this, the Permafrost Thaw Action Group of T-MOSAiC have developed a protocol for gathering integrated observations of multiple connected components of permafrost landscapes. It is integrated with a user-friendly app aimed at non-experts to facilitate collection and synthesis of data from across the Arctic. Recognizing the fundamental role of interactions between the different components of the permafrost system, we provide measurement guidelines for variables pertaining to snow, vegetation, hydrology, soil and permafrost in a single protocol. The measured variables include snow depth, vegetation height, water level, soil type, and thaw depth.The protocol locates all measurements on transects that are revisited throughout the year. The co-located measurements of multiple variables facilitate quantification of interactions between these variables and model-data integration.The protocol is geared toward non-experts, including citizen scientists. We provide video tutorials and a user-friendly app. The protocol uses simple measurements that do not require specialist equipment or skills. While variables that are more difficult to measure could not be included, we believe that the simplicity of the protocols will enable greater participation in data collection and thus an improved coverage of the permafrost region.Along with the protocol and app, we present the first results from the data collection which has been live now for several months, and details of how to get involved.

URL: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/871926

Back to the Top


© American Geosciences Institute