Permafrost Monthly Alerts (PMAs)

2018067105 Gentsch, Norman (Leibniz Universität, Institute of Soil Science, Hanover, Germany); Wild, Birgit; Mikutta, Robert; Capek, Petr; Diakova, Katla; Schrumpf, Marion; Turner, Stephanie; Minnich, Cynthia; Schaarschmidt, Frank; Shibistova, Olga; Schnecker, Jorg; Urich, Tim; Gittel, Antje; Santruckova, Hana; Barta, Jiri; Lashchinskiy, Nikolay; Fuss, Roland; Richter, Andreas and Guggenberger, Georg. Temperature response of permafrost soil carbon is attenuated by mineral protection: Global Change Biology, 24(8), p. 3401-3415, illus. incl. 2 tables, sketch map, 96 ref., August 2018.

Climate change in Arctic ecosystems fosters permafrost thaw and makes massive amounts of ancient soil organic carbon (OC) available to microbial breakdown. However, fractions of the organic matter (OM) may be protected from rapid decomposition by their association with minerals. Little is known about the effects of mineral-organic associations (MOA) on the microbial accessibility of OM in permafrost soils and it is not clear which factors control its temperature sensitivity. In order to investigate if and how permafrost soil OC turnover is affected by mineral controls, the heavy fraction (HF) representing mostly MOA was obtained by density fractionation from 27 permafrost soil profiles of the Siberian Arctic. In parallel laboratory incubations, the unfractionated soils (bulk) and their HF were comparatively incubated for 175 days at 5 and 15°C. The HF was equivalent to 70 ± 9% of the bulk CO2 respiration as compared to a share of 63 ± 1% of bulk OC that was stored in the HF. Significant reduction of OC mineralization was found in all treatments with increasing OC content of the HF (HF-OC), clay-size minerals and Fe or Al oxyhydroxides. Temperature sensitivity (Q10) decreased with increasing soil depth from 2.4 to 1.4 in the bulk soil and from 2.9 to 1.5 in the HF. A concurrent increase in the metal-to-HF-OC ratios with soil depth suggests a stronger bonding of OM to minerals in the subsoil. There, the younger 14C signature in CO2 than that of the OC indicates a preferential decomposition of the more recent OM and the existence of a MOA fraction with limited access of OM to decomposers. These results indicate strong mineral controls on the decomposability of OM after permafrost thaw and on its temperature sensitivity. Thus, we here provide evidence that OM temperature sensitivity can be attenuated by MOA in permafrost soils.

DOI: 10.1111/gcb.14316

2018062861 Clark, Chris D. (University of Sheffield, Department of Geography, Sheffield, United Kingdom) and Livingstone, Stephen J. Glacial curvilineations found along the southern sector of the Laurentide ice sheet and a hypothesis of formation involving subglacial slope failure in tunnel valleys and subglacial lakes: Earth Surface Processes and Landforms, 43(7), p. 1518-1528, illus., 31 ref., June 15, 2018.

First discovered in Poland, glacial curvilineations (GCLs) are enigmatic landforms comprising parallel sets of sinuous ridges and troughs of metres amplitude and around 150 m wavelength, found within kilometres-wide valleys interpreted as being produced by meltwater flowing subglacially. Their morphological and sedimentary characteristics and association with tunnel valleys has been described for some prominent Polish examples. From these observations the existing hypothesis is that they form as a consequence of erosion by longitudinal vortices that develop in subglacial floods. Here we report, for the first time, GCLs found along the southern sector of the Laurentide Ice Sheet in three northern states of the USA. Using mapping and topographic analysis from high resolution digital elevation models we report observations on their morphological properties and landform associations. We find aspects of their context and morphology difficult to explain using the existing hypothesis. We instead suggest that these glacial curvilineations are produced by subglacial bank and slope failures that locally widen tunnel valleys, or that occur near subglacial lake shorelines. Further investigation is required to test this hypothesis and to ascertain the mechanisms of proposed mass movements, which may have occurred by rotational or translational slope failure or by creep deformation. Our preferred mechanism is that such movements occurred where subglacial water was emplaced over previously perma-frozen ground. Under such circumstances, sediment blocks thawed by the water may then easily glide over a frozen decollement at low slope angles; analogous to subaerial active-layer glides in permafrost environments. Permafrost spring sapping may have provided lines of weakness for slope failure. If the requirement for permafrost is found to hold, then GCLs may become an important indicator of the palaeo-distribution of permafrost. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/esp.4324

2018062853 Guglielmin, Mauro (Insubria University, Department of Theoretical and Applied Sciences, Varese, Italy); Ponti, Stefano and Forte, Emanuele. The origins of Antarctic rock glaciers; periglacial or glacial features?: Earth Surface Processes and Landforms, 43(7), p. 1390-1402, illus. incl. 1 table, sects., 86 ref., June 15, 2018.

In extensively glaciarized permafrost areas such as Northern Victoria Land, rock glaciers are quite common and are considered postglacial cryotic landforms. This paper reveals that two rock glaciers in Northern Victoria Land (at Adelie Cove and Strandline) that are located close to the Italian Antarctic Station (Mario Zucchelli Station) should have the same origin, although they were previously mapped as Holocene periglacial landforms and subsequently considered ice-cored and ice-cemented rock glaciers, respectively. In fact, by integrating different geophysical investigations and borehole stratigraphy, we show that both landforms have similar internal structures and cores of buried glacier ice. Therefore, this kind of rock glacier is possibly related to the long-term creep of buried ice rather than to permafrost creep alone. This interpretation can be extended to the larger part of the features mapped as rock glaciers in Antarctica. In addition, a high-reflective horizon sub-parallel to the topographic surface was detected in Ground Probing Radar (GPR) data over a large part of the study area. Combining all the available information, we conclude that it cannot be straightforwardly interpreted as the base of the active layer but rather represents the top of a cryo-lithological unit characterized by ice lenses within sediments that could be interpreted as the transition zone between the active layer and the long-term permafrost table. More generally, knowledge of the subsurface ice content and, in particular, the occurrence of massive ice and its depth is crucial to make realistic and affordable forecasts regarding thermokarst development and related feedbacks involving GHG emissions, especially in the case of cryosoils rich in carbon content. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/esp.4320

2018067103 Wickland, Kimberly P. (U.S. Geological Survey, Boulder, CO); Waldrop, Mark P.; Aiken, George R.; Koch, Joshua C.; Jorgenson, M. Torre and Striegl, Robert G. Dissolved organic carbon and nitrogen release from boreal Holocene permafrost and seasonally frozen soils of Alaska: Environmental Research Letters, 13(6), Paper no. 065011, illus. incl. 2 tables, sketch maps, 63 ref., June 2018.

Permafrost (perennially frozen) soils store vast amounts of organic carbon (C) and nitrogen (N) that are vulnerable to mobilization as dissolved organic carbon (DOC) and dissolved organic and inorganic nitrogen (DON, DIN) upon thaw. Such releases will affect the biogeochemistry of permafrost regions, yet little is known about the chemical composition and source variability of active-layer (seasonally frozen) and permafrost soil DOC, DON and DIN. We quantified DOC, total dissolved N (TDN), DON, and DIN leachate yields from deep active-layer and near-surface boreal Holocene permafrost soils in interior Alaska varying in soil C and N content and radiocarbon age to determine potential release upon thaw. Soil cores were collected at three sites distributed across the Alaska boreal region in late winter, cut in 15 cm thick sections, and deep active-layer and shallow permafrost sections were thawed and leached. Leachates were analyzed for DOC, TDN, nitrate (NO₃ ^-), and ammonium (NH₄ ⁺) concentrations, dissolved organic matter optical properties, and DOC biodegradability. Soils were analyzed for C, N, and radiocarbon (¹⁴C) content. Soil DOC, TDN, DON, and DIN yields increased linearly with soil C and N content, and decreased with increasing radiocarbon age. These relationships were significantly different for active-layer and permafrost soils such that for a given soil C or N content, or radiocarbon age, permafrost soils released more DOC and TDN (mostly as DON) per gram soil than active-layer soils. Permafrost soil DOC biodegradability was significantly correlated with soil D¹⁴C and DOM optical properties. Our results demonstrate that near-surface Holocene permafrost soils preserve greater relative potential DOC and TDN yields than overlying seasonally frozen soils that are exposed to annual leaching and decomposition. While many factors control the fate of DOC and TDN, the greater relative yields from newly thawed Holocene permafrost soils will have the largest potential impact in areas dominated by organic-rich soils. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/aac4ad

2018066828 Aalto, Juha (University of Helsinki, Department of Geosciences and Geography, Helsinki, Finland); Karjalainen, O.; Hjort, J. and Luoto, M. Statistical forecasting of current and future circum-Arctic ground temperatures and active layer thickness: Geophysical Research Letters, 45(10), p. 4889-4898, illus. incl. sketch maps, 71 ref., May 28, 2018.

Mean annual ground temperature (MAGT) and active layer thickness (ALT) are key to understanding the evolution of the ground thermal state across the Arctic under climate change. Here a statistical modeling approach is presented to forecast current and future circum-Arctic MAGT and ALT in relation to climatic and local environmental factors, at spatial scales unreachable with contemporary transient modeling. After deploying an ensemble of multiple statistical techniques, distance-blocked cross validation between observations and predictions suggested excellent and reasonable transferability of the MAGT and ALT models, respectively. The MAGT forecasts indicated currently suitable conditions for permafrost to prevail over an area of 15.1 ± 2.8 ´ 10⁶ km². This extent is likely to dramatically contract in the future, as the results showed consistent, but region-specific, changes in ground thermal regime due to climate change. The forecasts provide new opportunities to assess future Arctic changes in ground thermal state and biogeochemical feedback. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2018GL078007

2018067108 Wei Shiping (China University of Geosciences, State Key Laboratory of Biogeology and Environmental Geology, Beijing, China); Cui Hongpeng; Zhu Youhai; Pang Shouji; Zhang Shuai; Dong Hailiang and Su Xin. Shifts of methanogenic communities in response to permafrost thaw results in rising methane emissions and soil property changes: Extremophiles, 22(3), p. 447-459, 62 ref., May 2018.

Permafrost thaw can bring negative consequences in terms of ecosystems, resulting in permafrost collapse, waterlogging, thermokarst lake development, and species composition changes. Little is known about how permafrost thaw influences microbial community shifts and their activities. Here, we show that the dominant archaeal community shifts from Methanomicrobiales to Methanosarcinales in response to the permafrost thaw, and the increase in methane emission is found to be associated with the methanogenic archaea, which rapidly bloom with nearly tenfold increase in total number. The mcrA gene clone libraries analyses indicate that Methanocellales/Rice Cluster I was predominant both in the original permafrost and in the thawed permafrost. However, only species belonging to Methanosarcinales showed higher transcriptional activities in the thawed permafrost, indicating a shift of methanogens from hydrogenotrophic to partly acetoclastic methane-generating metabolic processes. In addition, data also show the soil texture and features change as a result of microbial reproduction and activity induced by this permafrost thaw. Those data indicate that microbial ecology under warming permafrost has potential impacts on ecosystem and methane emissions.

DOI: 10.1007/s00792-018-1007-x

2018067100 Polishchuk, Y. M. (Ugra Research Institute of Information Technology, Khanty-Mansiysk, Russian Federation); Bogdanov, A. N.; Muratov, I. N.; Polishchuk, V. Y.; Lim, A.; Manasypov, R. M.; Shirokova, L. S. and Pokrovsky, O. S. Minor contribution of small thaw ponds to the pools of carbon and methane in the inland waters of the permafrost-affected part of the Western Siberian Lowland: Environmental Research Letters, 13(4), Paper no. 045002, illus. incl. 3 tables, sketch maps, 95 ref., April 2018.

Despite the potential importance of small (<1000 m²) thaw ponds and thermokarst lakes in greenhouse gas (GHG) emissions from inland waters of high latitude and boreal regions, these features have not been fully inventoried and the volume of GHG and carbon in thermokarst lakes remains poorly constrained. This is especially true for the vast Western Siberia Lowland (WSL) which is subject to strong thermokarst activity. We assessed the number of thermokarst lakes and their size distribution for the permafrost-affected WSL territory based on a combination of medium-resolution Landsat-8 images and high-resolution Kanopus-V scenes on 78 test sites across the WSL in a wide range of lake sizes (from 20 to 2´10⁸ m²). The results were in fair agreement with other published data for world lakes including those in circum-polar regions. Based on available measurements of CH₄, CO₂, and dissolved organic carbon (DOC) in thermokarst lakes and thaw ponds of the permafrost-affected part of the WSL, we found an inverse relationship between lake size and concentration, with concentrations of GHGs and DOC being highest in small thaw ponds. However, since these small ponds represent only a tiny fraction of the landscape (i.e. ~1.5% of the total lake area), their contribution to the total pool of GHG and DOC in inland lentic water of the permafrost-affected part of the WSL is less than 2%. As such, despite high concentrations of DOC and GHG in small ponds, their role in overall C storage can be negated. Ongoing lake drainage due to climate warming and permafrost thaw in the WSL may lead to a decrease in GHG emission potential from inland waters and DOC release from lakes to rivers. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/aab046

2018062620 Cook, Ann E. (Ohio State University, School of Earth Science, Columbus, OH) and Waite, William F. Archie's saturation exponent for natural gas hydrate in coarse-grained reservoirs: Journal of Geophysical Research: Solid Earth, 123(3), p. 2069-2089, illus. incl. 2 tables, sketch map, 101 ref., March 2018.

Accurately quantifying the amount of naturally occurring gas hydrate in marine and permafrost environments is important for assessing its resource potential and understanding the role of gas hydrate in the global carbon cycle. Electrical resistivity well logs are often used to calculate gas hydrate saturations, S_h, using Archie's equation. Archie's equation, in turn, relies on an empirical saturation parameter, n. Though n = 1.9 has been measured for ice-bearing sands and is widely used within the hydrate community, it is highly questionable if this n value is appropriate for hydrate-bearing sands. In this work, we calibrate n for hydrate-bearing sands from the Canadian permafrost gas hydrate research well, Mallik 5L-38, by establishing an independent downhole S_h profile based on compressional-wave velocity log data. Using the independently determined S_h profile and colocated electrical resistivity and bulk density logs, Archie's saturation equation is solved for n, and uncertainty is tracked throughout the iterative process. In addition to the Mallik 5L-38 well, we also apply this method to two marine, coarse-grained reservoirs from the northern Gulf of Mexico Gas Hydrate Joint Industry Project: Walker Ridge 313-H and Green Canyon 955-H. All locations yield similar results, each suggesting n ~ 2.5 ± 0.5. Thus, for the coarse-grained hydrate bearing (S_h > 0.4) of greatest interest as potential energy resources, we suggest that n = 2.5 ± 0.5 should be applied in Archie's equation for either marine or permafrost gas hydrate settings if independent estimates of n are not available. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JB015138

2018061029 Guo Donglin (Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing, China); Wang Aihui; Li Duo and Hua Wei. Simulation of changes in the near-surface soil freeze/thaw cycle using CLM4.5 with four atmospheric forcing data sets: Journal of Geophysical Research: Atmospheres, 123(5), p. 2509-2523, illus. incl. 3 tables, geol. sketch map, 79 ref., March 16, 2018.

Change in the near-surface soil freeze/thaw cycle is critical for assessments of hydrological activity, ecosystems, and climate change. Previous studies investigated the near-surface soil freeze/thaw cycle change mostly based on in situ observations and satellite monitoring. Here numerical simulation method is tested to estimate the long-term change in the near-surface soil freeze/thaw cycle in response to recent climate warming for its application to predictions. Four simulations are performed at 0.5° ´ 0.5° resolution from 1979 to 2009 using the Community Land Model version 4.5, each driven by one of the four atmospheric forcing data sets (i.e., one default Climate Research Unit-National Centers for Environmental Prediction [CRUNCEP] and three newly developed Modern Era Retrospective-Analysis for Research and Applications, Climate Forecast System Reanalysis, and European Centre for Medium-Range Weather Forecasts Reanalysis Interim). The observations from 299 weather stations in both Russia and China are employed to validate the simulated results. The results show that all simulations reasonably reproduce the observed variations in the ground temperature, the freeze start and end dates, and the freeze duration (the correlation coefficients range from 0.47 to 0.99, and the Nash-Sutcliffe efficiencies range from 0.19 to 0.98). Part of the simulations also exactly simulate the trends of the ground temperature, the freeze start and end dates, and the freeze duration. Of the four simulations, the results from the simulation using the CRUNCEP data set show the best overall agreement with the in situ observations, indicating that the CRUNCEP data set could be preferentially considered as the basic atmospheric forcing data set for future prediction. The simulated area-averaged annual freeze duration shortened by 8.03 days on average from 1979 to 2009, with an uncertainty (one standard deviation) of 0.67 days caused by the different atmospheric forcing data sets. These results address the performance of numerical model in simulating the long-term changes in the near-surface soil freeze/thaw cycle and the role of different atmospheric forcing data sets in the simulation, which are useful for the prediction of future freeze/thaw dynamics. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JD028097

2018064574 Weckwerth, Piotr (Nicolaus Copernicus University, Department of Geomorphology and Palaeogeography of Quaternary, Poland); Gren, Katarzyna and Sobota, Ireneusz. Morphology and surficial sediments of the Waldemar River confined outwash fan (Kaffioyra, Svalbard): Bulletin of Geography, Physical Geography Series, 13(1), p. 61-70, illus. incl. 2 tables, sketch map, 48 ref., December 2017.

The development and evolution of confined outwash fans in high Arctic regions depend on the rate of meltwater discharge, which is directly related to the glacier ablation rate, in turn associated with climate conditions. Other factors controlling outwash fan morphology (e.g. depth and width of distributive channels) are processes of fluvial erosion, and the transport and deposition of sediments. These factors have not previously been considered together in relation to the evolution of the confined outwash fans which are commonly incised into the top of permafrost in the forefields of subpolar glaciers and in mountains in high Arctic regions. Morphology and surficial sediments of a confined outwash fan of the Waldemar River (NW Spitsbergen, Svalbard) were analysed on the basis of geomorphological and sedimentological studies. The results of our investigations show multiple relations between the depth and width of distributary channels, fan slope and textural features of glaciofluvial surficial sediments supplied into the fluvial system from the glacier and from lateral fluvial erosion of permafrost

DOI: 10.1515/bgeo-2017-0014

2018060924 Zhang, Xiaowen (University of Florida, Department of Geological Sciences, Gainsville, FL); Bianchi, Thomas S.; Cui, Xingqian; Rosenheim, Brad E.; Ping, Chien-Lu; Hanna, Andrea J. M.; Kanevskiy, Mikhail; Schreiner, Kathryn M. and Allison, Mead A. Permafrost organic carbon mobilization from the watershed to the Colville River delta; evidence from ¹⁴C ramped pyrolysis and lignin biomarkers: Geophysical Research Letters, 44(22), p. 11,491-11,500, illus. incl. sketch maps, 84 ref., November 28, 2017.

The deposition of terrestrial-derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis-oxidation radiocarbon analysis (RPO ¹⁴C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo-mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial-derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL075543

2018061690 Darnell, K. N. (University of Texas at Austin, Jackson School of Geosciences, Department of Geological Sciences, Austin, TX); Flemings, P. B. and DiCarlo, D. Subsurface injection of combustion power plant effluent as a solid-phase carbon dioxide storage strategy: Geophysical Research Letters, 44(11), p. 5521-5530, illus., 42 ref., June 16, 2017.

Long-term geological storage of CO₂ may be essential for greenhouse gas mitigation, so a number of storage strategies have been developed that utilize a variety of physical processes. Recent work shows that injection of combustion power plant effluent, a mixture of CO₂ and N₂, into CH₄ hydrate-bearing reservoirs blends CO₂ storage with simultaneous CH₄ production where the CO₂ is stored in hydrate, an immobile, solid compound. This strategy creates economic value from the CH₄ production, reduces the preinjection complexity since costly CO₂ distillation is circumvented, and limits leakage since hydrate is immobile. Here we explore the phase behavior of these types of injections and describe the individual roles of H₂O, CO₂, CH₄, and N₂ as these components partition into aqueous, vapor, hydrate, and liquid CO₂ phases. Our results show that CO₂ storage in subpermafrost or submarine hydrate-forming reservoirs requires coinjection of N₂ to maintain two-phase flow and limit plugging. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL073663

2018060407 Shelef, Eitan (Los Alamos National Laboratory, Earth and Environmental Science Division, Los Alamos, NM); Rowland, Joel C.; Wilson, Cathy J.; Hilley, George E.; Mishra, Umakant; Altmann, Garrett L. and Ping, Chien-Lu. Large uncertainty in permafrost carbon stocks due to hillslope soil deposits: Geophysical Research Letters, 44(12), p. 6134-6144, illus. incl. sketch maps, 68 ref., June 28, 2017.

Northern circumpolar permafrost soils contain more than a third of the global soil organic carbon pool (SOC). The sensitivity of this carbon pool to a changing climate is a primary source of uncertainty in simulation-based climate projections. These projections, however, do not account for the accumulation of soil deposits at the base of hillslopes (hill toes) and the influence of this accumulation on the distribution, sequestration, and decomposition of SOC in landscapes affected by permafrost. Here we combine topographic models with soil profile data and topographic analysis to evaluate the quantity and uncertainty of SOC mass stored in perennially frozen hill toe soil deposits. We show that in Alaska this SOC mass introduces an uncertainty that is >200% the state-wide estimates of SOC stocks (77 Pg C) and that a similarly large uncertainty may also pertain at a circumpolar scale. Soil sampling and geophysical imaging efforts that target hill toe deposits can help constrain this large uncertainty. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL073823

2018065711 Wang Qingfeng (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Zhang Tingjun; Jin Huijun; Cao Bin; Peng Xiaoqing; Wang Kang; Li Lili; Guo Hong; Liu Jia and Cao Lin. Observational study on the active layer freeze-thaw cycle in the upper reaches of the Heihe River of the north-eastern Qinghai-Tibet Plateau: in Large Asian rivers 9; Part I (Jiang Tong, editor; et al.), Quaternary International, 440(Part B), p. 13-22, illus. incl. 1 table, sketch map, 36 ref., June 10, 2017.

Observational data collection on permafrost and active layer freeze-thaw cycle is extremely limited in the upper reaches of the Heihe River (URHHR) in the Qilian Mountains of the north-eastern Qinghai-Tibet Plateau. It acts as a bottleneck, restricting the hydrological effects of the changes in the permafrost and active layer in the Heihe River Basin. Using soil temperature, moisture and air temperature data collected from the four active layer observation sites (AL1, AL3, AL4 and AL7) established in the alpine permafrost regions in the URHHR, from 2013 to 2014, the region's active layer freeze-thaw cycle and the soil hydrothermal dynamics were comparatively analysed. As the elevation increased from 3700 m a.s.l. to 4132 m a.s.l., the mean annual ground temperatures (MAGTs) of the active layer and the active layer thicknesses (ALTs) decreased, the onset date of soil freeze of the active layer occurred earlier and the soil freeze rate increased. However, the onset date of soil thaw and the thaw rate did not exhibit significant trends. Compared to the thaw process, the duration of the active layer freeze process was significantly shortened and its rate was significantly higher. The soil freeze from bottom to top did not occur earlier than that from top to bottom. Furthermore, as elevation increased, the proportion of the bottom-up freeze layer thickness increased. The soil moisture in the thaw layer continuously moved to the freeze front during the active layer's two-way freeze process, causing the thaw layer to be dewatered. The seasonal thaw process resulted in significant reduction of the soil water content in the thaw layer, accounting for the high ice content in the vicinity of the permafrost table. Controlled by elevation, the active layer's seasonal freeze-thaw cycle was also affected by local factors, such as vegetation, slope, water (marsh water and super-permafrost water), lithology and water (ice) content. This study provides quantitative data that identify, simulate and predict the hydrological effects of the changes in the permafrost and active layer of the Heihe River Basin.

DOI: 10.1016/j.quaint.2016.08.027

2018061693 Zhang Guoqing (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Beijing, China); Yao Tandong; Shum, C. K.; Yi, Shuang; Yang Kun; Xie, Hongjie; Feng Wei; Bolch, Tobias; Wang Lei; Behrangi, Ali; Zhang Hongbo; Wang Weicai; Xiang Yang and Yu Jinyuan. Lake volume and groundwater storage variations in Tibetan Plateau's endorheic basin: Geophysical Research Letters, 44(11), p. 5550-5560, illus. incl. sketch maps, 67 ref., June 16, 2017.

The Tibetan Plateau (TP), the highest and largest plateau in the world, with complex and competing cryospheric-hydrologic-geodynamic processes, is particularly sensitive to anthropogenic warming. The quantitative water mass budget in the TP is poorly known. Here we examine annual changes in lake area, level, and volume during 1970s-2015. We find that a complex pattern of lake volume changes during 1970s-2015: a slight decrease of -2.78 Gt yr^-1 during 1970s-1995, followed by a rapid increase of 12.53 Gt yr^-1 during 1996-2010, and then a recent deceleration (1.46 Gt yr^-1) during 2011-2015. We then estimated the recent water mass budget for the Inner TP, 2003-2009, including changes in terrestrial water storage, lake volume, glacier mass, snow water equivalent (SWE), soil moisture, and permafrost. The dominant components of water mass budget, namely, changes in lake volume (7.72 ± 0.63 Gt yr^-1) and groundwater storage (5.01 ± 1.59 Gt yr^-1), increased at similar rates. We find that increased net precipitation contributes the majority of water supply (74%) for the lake volume increase, followed by glacier mass loss (13%), and ground ice melt due to permafrost degradation (12%). Other term such as SWE (1%) makes a relatively small contribution. These results suggest that the hydrologic cycle in the TP has intensified remarkably during recent decades. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL073773

2018060377 Ludwig, Patrick (University of Cologne, Institute for Geophysics and Meteorology, Cologne, Germany); Pinto, Joaquim G.; Raible, Christoph C. and Shao, Yaping. Impacts of surface boundary conditions on regional climate model simulations of European climate during the last glacial maximum: Geophysical Research Letters, 44(10), p. 5086-5095, illus. incl. sketch maps, 48 ref., May 28, 2017.

We examine the influences of North Atlantic sea surface temperatures (SSTs) and vegetation on regional climate simulations over Europe during the Last Glacial Maximum (LGM). Simulated regional temperature and precipitation patterns over Europe are considerably improved when using revised SSTs based on proxy data. Likewise, the simulated permafrost is more accurately reproduced with the SST modifications. These improvements are partially related to the changed regional atmospheric circulation due to the revised SSTs, leading to colder and drier conditions over Western Europe. Further sensitivity tests with prescribed vegetation for LGM conditions provide evidence of the sensitivity of the simulated glacial climate. This study reveals the importance of considering more realistic SST and vegetation boundary conditions for a more accurate representation of regional climate variability under glacial conditions. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL073622

2018067110 Jones, Miriam C. (U. S. Geological Survey, Reston, VA); Harden, Jennifer; O'Donnell, Jonathan; Manies, Kristen; Jorgenson, Torre; Treat, Claire and Ewing, Stephanie. Rapid carbon loss and slow recovery following permafrost thaw in boreal peatlands: Global Change Biology, 23(3), p. 1109-1126, illus. incl. 1 table, 60 ref., March 2017.

Permafrost peatlands store one-third of the total carbon (C) in the atmosphere and are increasingly vulnerable tothaw as high-latitude temperatures warm. Large uncertainties remain about C dynamics following permafrost thawin boreal peatlands. We used a chronosequence approach to measure C stocks in forested permafrost plateaus (forest)and thawed permafrost bogs, ranging in thaw age from young (< 10 years) to old (>100 years) from two interior Alaska chronosequences. Permafrost originally aggraded simultaneously with peat accumulation (syngenetic permafrost) at both sites. We found that upon thaw, C loss of the forest peat C is equivalent to ~30% of the initial forestC stock and is directly proportional to the prethaw C stocks. Our model results indicate that permafrost thaw turned these peatlands into net C sources to the atmosphere for a decade following thaw, after which post-thaw bog peat accumulation returned sites to net C sinks. It can take multiple centuries to millennia for a site to recover its prethaw C stocks; the amount of time needed for them to regain their prethaw C stocks is governed by the amount of C that accumulated prior to thaw. Consequently, these findings show that older peatlands will take longer to recover pre-thaw C stocks, whereas younger peatlands will exceed prethaw stocks in a matter of centuries. We conclude that theloss of sporadic and discontinuous permafrost by 2100 could result in a loss of up to 24 Pg of deep C from permafrost peatlands.

DOI: 10.1111/gcb.13403

2018067109 Mackelprang, Rachel (California State University Northridge, Northridge, CA); Burkert, Alexander; Haw, Monica; Mahendrarajah, Tara; Conaway, Christopher H.; Douglas, Thomas A. and Waldrop, Mark P. Microbial survival strategies in ancient permafrost; insights from metagenomics: The ISME Journal, 11(10), p. 2305-2318, illus., 96 ref., 2017.

In permafrost (perennially frozen ground) microbes survive oligotrophic conditions, sub-zero temperatures, low water availability and high salinity over millennia. Viable life exists in permafrost tens of thousands of years old but we know little about the metabolic and physiological adaptations to the challenges presented by life in frozen ground over geologic time. In this study we asked whether increasing age and the associated stressors drive adaptive changes in community composition and function. We conducted deep metagenomic and 16?S rRNA gene sequencing across a Pleistocene permafrost chronosequence from 19?000 to 33?000 years before present (kyr). We found that age markedly affected community composition and reduced diversity. Reconstruction of paleovegetation from metagenomic sequence suggests vegetation differences in the paleo record are not responsible for shifts in community composition and function. Rather, we observed shifts consistent with long-term survival strategies in extreme cryogenic environments. These include increased reliance on scavenging detrital biomass, horizontal gene transfer, chemotaxis, dormancy, environmental sensing and stress response. Our results identify traits that may enable survival in ancient cryoenvironments with no influx of energy or new materials.

DOI: 10.1038/ismej.2017.93

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2018067111 Paturi, Sairavichand. Groundwater flow in a vertical plane at the interface of permafrost: 70 p., illus. incl. tables, sketch maps, 39 ref., Master's, August 2017, University of Alaska at Fairbanks, Fairbanks, AK.

Groundwater dynamics in discontinuous permafrost aquifers are complex. The topography of permafrost redirects flow in difficult-to-predict directions that can be tens of degrees off from the regional flow direction. Large zones of permafrost vertically separate aquifers into supra and sub-permafrost portions. The flow dynamics in each portion of the aquifer may be dissimilar due to different controlling boundary conditions. In areas of discontinuities in permafrost, known as open taliks, groundwater in the two portions of the aquifer may mix. These areas of mixing are the focus of this study, in particular, the groundwater dynamics in taliks located in the floodplain of lower reaches of rivers. The study hypothesizes that groundwater flow in floodplain taliks of lower reaches of rivers will bifurcate between the supra and sub-permafrost portions of a discontinuous permafrost aquifer. To test this hypothesis gradient, magnitudes and flow directions were determined at several depths ranging from the water table to 150 ft. (45.7 m) below ground surface, using a linear interpolation scheme in various locations in a floodplain talik. Errors in water level measurements due to instrument errors as well as vertically moving wells were propagated into the gradient calculations by Monte Carlo analysis. Results from this research show that a vertical divide in groundwater flow forms a short distance below the top of permafrost. Groundwater flow above the divide routes into the unconfined supra-permafrost portion of the aquifer. Water below the divide flows into the confined portion of the aquifer below permafrost. The position of the vertical groundwater divide may adjust in relation to the water table position. Additionally, a methodology is presented for stochastically propagating measurement errors into gradient analyses by Monte Carlo analysis. Understanding the flow dynamics in discontinuous permafrost aquifers is key to the understanding of contaminant transport, aquifer recharge, and resource development in subarctic environments.

URL: https://scholarworks.alaska.edu/bitstream/handle/11122/7898/Paturi_S_2017.pdf?se ...

2018062755 Heslop, Joanne K. Permafrost organic matter quality and biolability in the Vault Lake thermokarst environment, interior Alaska, USA: 172 p., illus. incl. 15 tables, 264 ref., Doctoral, 2017, University of Alaska at Fairbanks, Fairbanks, AK.

Warming and thawing of permafrost soils removes a major barrier to soil organic carbon (SOC) mineralization, leading to the mobilization and microbial degradation of previously frozen, inactive permafrost organic carbon (OC) into the greenhouse gases carbon dioxide (CO₂) and methane (CH₄). Many thermokarst (thaw) lakes formed in permafrost-dominated landscapes have high rates of CO₂ and CH₄ emission; however, the composition and biodegradability of the thawed permafrost OC as they relate to the relative magnitudes of anaerobic OC mineralization at different depths throughout the vertical profile of a thermokarst-lake talik system have, to my knowledge, never been measured. My research examined OC composition and mineralization potentials at the Vault Creek (VC) permafrost tunnel and Vault Lake, located 20 km north of Fairbanks, Alaska, USA, to better constrain these uncertainties. I found that, in a 590-cm long sediment core collected from the center of Vault Lake, whole-column CH₄ production is dominated by methanogenesis in the organic-rich mud facies, which occurred in the surface 0 to 152 cm. CH₄ production potential rates positively associated with substrate availability (carbon and nitrogen concentrations) and the relative abundances of terrestrially-derived organic matter compounds (alkanes, alkenes, lignin products, and phenols and phenolic precursors), measured using pyrolysis-gas chromatography-mass spectrometry. Temperature sensitivity analyses conducted on a subset of samples from the Vault Lake sediment core suggest century-scale time since permafrost thaw affects temperature sensitivities of CH₄ production. Freshly-thawed taberite sediments at the base of the talik (thaw bulb) were most sensitive to warming at lower incubation temperatures (0 °C to 3 °C), while the overlying taberite sediments thawed in situ longer periods of time (up to 400 years based on radiocarbon dating) did not experience statistically significant increases in CH₄ production until higher incubation temperatures (10 °C to 25 °C). Finally, using anaerobic incubations and ultrahigh-resolution mass spectrometry of water-extractable organic matter along a 12-m yedoma profile in the VC permafrost tunnel, I show that yedoma OC biolability increases with depth as indicated by increasing proportions of aliphatics and peptides (reduced, high H/C compounds). These compounds also positively correlated with anaerobic CO₂ and CH₄ production, and corresponded to high proportions (5.6% to 118 %) of OC mineralization rates in incubations. This suggests that as yedoma permafrost thaws beneath a thermokarst lake greenhouse gas production potentials may increase with thaw depth.

URL: https://scholarworks.alaska.edu/bitstream/handle/11122/7607/Heslop_J_2017.pdf?se ...

2018066388 Kaiser, Christianese. Estimating atmospheric methane emission by mineral Cryosols in the Arctic region using the explicit high affinity methanotroph (XHAM) model: 41 p., illus. incl. 2 tables, 16 ref., Bachelor's, 2017, Princeton University, Princeton, NJ.

Methane is a powerful greenhouse gas that needs to be closely regulated in order to mitigate its effect on climate change. This is especially important in the permafrost affected Arctic region that has a large carbon reservoir, which, if thawed, would likely be mineralized into greenhouse gases and increase warming. For this reason, much attention has been paid to carbon-rich cryosols and methane emissions in the Arctic region. However, there is a large area of carbon-poor cryosols that may have the potential to be methane uptaking sites especially due to the activity of high-affinity methanotrophic (HAM) bacteria. Because HAM activity has been reported in carbon-poor cryosols and the carbon-poor cryosols are 87% of the Arctic region, Arctic will likely be a net sink for methane. To estimate the net methane flux in the Arctic region where HAM have been found, the eXplicit High Affinity Methanotroph (XHAM) model was scaled up to simulate methane fluxes in the Arctic region for 2004, 2006, 2008, 2010, and 2012. This model took the soil moisture and surface temperature and simulated the change in biomass and activity of both methanogens and methanotrophs down a 1m column for each year-long period. Methane production and consumption and net fluxes were computed for each month of simulation. These values were compared to determine seasonal and inter-annual trends and determine whether the Arctic was an overall sink for atmospheric methane. The hypothesis that the Arctic region was an overall sink for atmospheric methane was not validated through this project.

2018062757 Whitley, Matthew Allen. Assessment of LiDAR and spectral techniques for high-resolution mapping of permafrost on the Yukon-Kuskokwim Delta, Alaska: 96 p., illus. incl. 15 tables, 68 ref., Master's, 2017, University of Alaska at Fairbanks, Fairbanks, AK.

The Yukon-Kuskokwim Delta (YKD) is one of the largest and most ecologically productive coastal wetland regions in the pan-Arctic. Formed by the Yukon and Kuskokwim Rivers flowing into the Bering Sea, nearly 130,000 square kilometers of delta support 23,000 Alaskan Natives living subsistence lifestyles. Permafrost on the outer delta commonly occurs on the abandoned floodplain deposits. Ground ice in the soil raises surface elevations on the order of 1-2 meters, creating plateaus on the landscape. Better drainage on the plateaus supports distinct Sphagnum-rich vegetation, which in turn protects the permafrost from rising air temperatures with low thermal conductivity during the summer. This ecosystem-protected permafrost is thus vulnerable to disturbances from rising air temperatures, vegetation mortality, and inland storm surges, which have been known to flood up to 37 km inland. This thesis assesses several novel techniques to map permafrost distribution at high-resolution on the YKD. Accurate baseline maps of permafrost extent are critical for a variety of applications, including long-term monitoring. As air and ground temperatures rise across the Arctic, monitoring landscape change is important for understanding permafrost degradation processes (e.g. thermokarst) and greenhouse gas dynamics from the local to global scales. This thesis separately explored the value of Light Detection And Ranging (LiDAR) and spectral datasets as tools to map permafrost at a high spatial resolution. Furthermore, this thesis sought to automate these processes, with the vision of high-resolution mapping over large spatial extents. Fieldwork was conducted in July 2016 to both parameterize and then validate the mapping efforts. The LiDAR mapping extent assessed a 135 km² area (~15% permafrost cover), and the spectral mapping extent assessed an 8 km² area (~20% permafrost cover). For the LiDAR dataset, the use of a simple elevation threshold informed by field ground truth values provided a permafrost map with 94.9% accuracy. This simple approach was possible because of the extremely flat terrain. For the spectral datasets, an ad-hoc masking technique was developed using a combination of texture analysis, principal component analysis, and morphological filtering. Two contrasting workflows were evaluated with fully-automated and semi-automated methods with mixed results. The highest mapping accuracy was 89.4% and the lowest was 79.1%, though the error of omission in mapping the permafrost remained high (7.02 - 59.7%) for most analyses. The spectral mapping algorithms did not replicate well across different high-resolution images, raising questions about the viability of using spectral methods alone to track thermokarst and landscape change over time. However, incorporating the spectral methods explored in this analysis with other datasets (e.g. LiDAR) has the potential to increase mapping accuracies. Both the methods and the results of this thesis enhance permafrost mapping efforts on the YKD, and provide a good first step to monitoring landscape change in the region.

URL: https://scholarworks.alaska.edu/bitstream/handle/11122/7650/Whitley_A_2017.pdf?s ...

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2018062000 Deline, Philip; Boden, Xavier and Ravanel, Ludovic, editors. 5th European conference on Permafrost; book of abstracts: Abstracts – European Conference on Permafrost, 5, 1055 p., illus., 2018. Meeting: 5th European Conference on Permafrost, June 23 – July 1, 2018, Chamonix, France.

The 5th European conference on Permafrost was held in Chamonix, France from June 23 to July 1, 2018. The conference program can be downloaded at URL: https://eucop2018.sciencesconf.org/resource/page/id/20

2018061275 Almatari, Abraham L. (University of Tennessee at Knoxville, Center for Environmental Biotechnology, Knoxville, TN); Williams, Daniel; Spirina, Elena; Pfiffner, Susan; Lloyd, Karen; Rivkina, Elizaveta and Vishnivetskaya, Tatiana. Microbial diversity of Siberian permafrost [abstr.]: in Geological Society of America, Southeastern Section, 67th annual meeting, Abstracts with Programs - Geological Society of America, 50(3), Abstract no. 37-8, April 2018. Meeting: Geological Society of America, Southeastern Section, 67th annual meeting, April 12-13, 2018, Knoxville, TN. NSF grants DEB-1442262 and IIA-1358155.

This study explores diversity of microbial communities with respects to geological origin, age, and depth. Samples collected in Northern Siberia to a maximum depth of 24.6 meters along the Alazeya River are freshwater lake origin. Cores were collected with a slow rotary drill that prevented down-hole contamination using quality assurance and quality control procedures. Collected cores were subsampled with sterile knife into sterile Whirl-Pak bags in the mobile field laboratory for later microbiological and molecular analyses DNA was isolated from these samples using Fast Spin DNA Kit for Soil^R. The 16S rRNA gene was amplified using 27F and 1492R with a further nested amplification using 515F and 806R primers. All samples were cleaned and concentrated using DNA Clean & Concentrator^R Kit (Zymo Research). DNA concentration was measured ranging from 1.2-83 ng/mL. After confirming DNA presence without contamination using Agilent Automatic Gel Electrophoresis, correct DNA concentration for MiSeq was determined using qPCR. Sequencing data were obtained using Illumina MiSeq at the Center for Environmental Biotechnology, University of Tennessee. Diversity analyses were done using the CLC Genomics Workbench with the Greengenes 16S rRNA gene database as reference. The OTUs were defined at 95% sequence similarity threshold. We observed that the samples in bore hole AL1 at depths 1.75-1.8 m and 2.95-3.0 m have a greater alpha diversity than samples from depths of 22.9 m and 24.5-24.6 m. Shallow depths of 1-3 m dominated by Actinobacteria at 47-60%, which decreased with depth up to 1-6% in the deeper sediments (23-25 m). On the contrary Firmicutes were more abundant (46-87%) in the deeper sediments then in the shallower depths, 5-35%. We saw changes in bacterial community from shallow permafrost sediments to deeper strata from aerobic non-spore-forming high GC Gram-positive Actinobacteria to anaerobic spore-forming low GC Gram-positive Firmicutes. The deepest permafrost sample was different and we detected a lot of Betaproteobacteria, Burkholderia, which are Gram-negative aerobic bacteria that often found in decaying organic matter. Microbial diversity data from the permafrost strata will add to our understanding of polar microbial ecology. This research is supported by NSF DEB 1442262 and NSF IIA 1358155.

2018064915 Batchelor, Cameron J. (University of Wisconsin at Madison, Department of Geology, Madison, WI); Orland, Ian J.; Marcott, Shaun A.; Slaughter, Richard and Edwards, R. Lawrence. A high-precision U-Th chronology of calcite deposition at Cave of the mounds, Wisconsin, and its implications for climate and permafrost in the late Pleistocene [abstr.]: in Geological Society of America, North-Central Section, 52nd annual meeting, Abstracts with Programs - Geological Society of America, 50(4), Abstract no. 1-5, April 2018. Meeting: Geological Society of America, North-Central Section, 52nd annual meeting, April 16-17, 2018, Ames, IA.

Permafrost forms when mean annual air temperatures are consistently below freezing, and it plays a critical role in a diverse array of environmental and climatic systems, including terrestrial carbon storage and subglacial ice sheet processes. Our understanding of late Pleistocene permafrost extent in the upper Midwest is temporally restricted to the last 25 ka and primarily derived from radiocarbon dates. Fortunately, expansive areas of the upper midcontinent of North America are underlain by cave carbonates (speleothems), which can be precisely dated using the ²³⁰Th-²³⁴U chronometer to 600 ka (Edwards et al., 1987). Since speleothem growth requires water, and therefore temperatures above freezing, these deposits can be used as a tool to constrain the extent of past permafrost and to better reconstruct pre-Last Glacial Maximum (LGM) climate near the Laurentide Ice Sheet (LIS) margin. Seventeen different speleothems were sampled from Cave of the Mounds, a cave located in the unglaciated Driftless Area of southwestern Wisconsin. This cave represents an ideal study site because it is located <20 km from the maximum extent of the LIS margin during the LGM. A total of 132 U-series dates were analyzed and span several glacial-interglacial cycles, ranging from 257-2 ka. Over this time period, these data distinguish a notable period of no calcite growth (hiatus) from 33 to 14 ka that overlaps Marine Isotope Stage (MIS) 2. The end of this hiatus (14 ka) corresponds with previously published geomorphological observations that constrain the onset of permafrost retreat in this area (Mickelson et al., 1983; Attig et al., 1989; Clayton et al, 2001). Our results demonstrate that between 233 and 33 ka, there is no significant hiatus in speleothem growth at Cave of the Mounds. We conclude that over the last two LIS advances (MIS 2, 6), the only prolonged duration of continuous permafrost in southwestern Wisconsin occurred relatively late during the last glacial period, which has major implications for constraining permafrost extent and climate conditions at these latitudes prior to the LGM.

2018066894 Caron, Olivier J. (Illinois State Geological Survey, Champaign, IL) and Curry, B. Brandon. Genesis and minimum ages of ice-marginal lakes and ice-walled lakes plains on the Valparaiso morainic system in Will County, Illinois (USA) [abstr.]: in Geological Society of America, North-Central Section, 52nd annual meeting, Abstracts with Programs - Geological Society of America, 50(4), Abstract no. 25-5, April 2018. Meeting: Geological Society of America, North-Central Section, 52nd annual meeting, April 16-17, 2018, Ames, IA.

In Will County, Illinois, we have identified three types of lakes intimately related to the ablation of dead-ice permafrost of the last glaciation: ice-walled lake plains, an ice-marginal lake, and a lake formed by a collapsed tunnel valley. The ice-walled lake plains occur on ground moraine between the Rockdale and Manhattan Moraines. Both moraines were eroded by the ca. 19,000 cal yr BP Kankakee Torrent. Regional data indicate that the moraines formed between about 22,500 and 20,500 cal yr BP. We obtained seven sediment cores from an ice-walled lake, and washed more than 20 m of core that yielded enough material for one radiocarbon age: 19,170±130 cal yr BP. As a minimum age for the Manhattan Moraine, the age is consistent with the regional data. A second lake type, interpreted as a lake marginal to the Westmont Moraine of the Valparaiso Morainic System, is named Glacial Lake Pine. On the east side of the lake deposit is a long, curving ridge with geomorphic characteristics of an ice-walled lake. We interpret this feature to be an ice-walled lake that was overridden by ice that formed the Westmont Moraine. Like the previous example, the lake provided little material for radiocarbon dating, but has yielded two ages: 18,490±85 and 18,700±60 cal yr BP. These ages are consistent with the Valparaiso Morainic System post-dating the Kankakee Torrent. The third lake type is unusually long and narrow (4 km by 1.5 km), and inset in the glacial drift, including the Westmont Moraine. The orientation, size, and form of Eagle Lake compared to the surrounding landscape indicates an origin through collapse of a tunnel valley. The basin contains at least 19 m of fossiliferous sediment. Radiocarbon ages from near the base and top of the sampled succession date from 16,250±80 to 3,150±50 cal yr BP. The discrepancy in ages between Eagle Lake and Glacial Lake Pine, about 2,000 years, indicates that collapse of the tunnel valley associated with Eagle Lake involved melting of deeply buried ice. Glacial Lake Pine, on the other hand, formed due to melting of near-surface dead-ice permafrost shortly after formation of the Westmont Moraine.

2018061232 Swezey, Christopher S. (U. S. Geological Survey, Reston, VA). Carolina Bays of the U.S. Atlantic Coastal Plain are relict thermokarst lakes that formed episodically during the last glaciation [abstr.]: in Geological Society of America, Southeastern Section, 67th annual meeting, Abstracts with Programs - Geological Society of America, 50(3), Abstract no. 32-11, April 2018. Meeting: Geological Society of America, Southeastern Section, 67th annual meeting, April 12-13, 2018, Knoxville, TN.

New studies of the U.S. Atlantic Coastal Plain using LiDAR data and optically stimulated luminescence (OSL) ages have revealed the presence of widespread eolian sands from Delaware to Georgia that were active episodically ~92-5 thousand years ago (ka) but are now stabilized by vegetation. These sands are present in river valleys, on upland terraces, in the Carolina Sandhills, and adjacent to Carolina Bays. Some of these sands form low-relief ridges on the south and east margins of Carolina Bays, which are oriented oval depressions. Some Carolina Bays show cross-cutting relations with other bays. Other Carolina Bays show different stratigraphic relations with respect to eolian dunes in river valleys. Examples from South Carolina include Bear Swamp that is inset into (i.e., younger than) eolian dunes in the valley of the Great Pee Dee River, and Big Bay that is overlain by (i.e., older than) eolian dunes in the valley at the confluence of the Congaree and Wateree Rivers. Cores in Carolina Bays and their associated ridges reveal a few meters of sand and/or muddy sand above an unconformity on various older fine-grained substrates that do not show signs of disturbance. Most published OSL ages from Carolina Bay sand ridges range from ~45-8 ka. Some bays have multiple sand ridges, and ridges closer to individual bays yield younger OSL ages. The stratigraphic relations and OSL ages suggest that Carolina Bays are relict features that did not form during one event of limited duration. Instead, they formed episodically during the same time interval as other eolian sands of the coastal plain (e.g., during the last glaciation when conditions were colder, drier, and windier). The interpretation of Carolina Bays as relict features that formed during the last glaciation suggests that they may be thermokarst lakes such as are present today in high-latitude regions. These lakes develop as a result of thaw and collapse of frozen ground, with subsequent modification by lacustrine and eolian processes. The distribution of Carolina Bays thus may provide information about former distribution of frozen ground. Although the southern limit of continuous permafrost during the last glaciation is thought to have been located in Virginia, deep frozen ground may have extended much farther south into areas where Carolina Bays are present.

2018064353 Bahadory, Taimaz (Memorial University of Newfoundland, Department of Physics and Physical Oceanography, St. John's, NL, Canada) and Tarasov, Lev. What is the phase space of the last glacial inception? [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10784-2, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Would the ice and climate pattern of glacial inception changed much with small tweaks to the initial Eemian climate state? Given the very limited available geological constraints, what is the range of potential spatio-temporal patterns of ice sheet inception and associated climate? What positive and negative feedbacks between ice, atmospheric and ocean circulation, and vegetation dominate glacial inception? As a step towards answering these questions, we examine the phase space of glacial inception in response to a subset of uncertainties in a coupled 3D model through an ensemble of simulations. The coupled model consists of the GSM (Glacial Systems Model) and LOVECLIM earth systems model of intermediate complexity. The former includes a 3D ice sheet model, asynchronously coupled glacio isostatic adjustment, surface drainage solver, and permafrost resolving bed thermal model. The latter includes an ocean GCM, atmospheric component, dynamic/thermodynamic seaice, and simplified dynamical vegetation. Our phase space exploration probes uncertainties in: initial conditions, downscaling and upscaling, the radiative effect of clouds, snow and ice albedo, precipitation parameterization, and freshwater discharge. The probe is constrained by model fit to present day climate and LGM climate. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-10784.pdf

2018066447 Chen Lemin (Tongji University, College of Surveying and Geo-Informatics, Shanghai, China); Qiao Gang and Lu Ping. Surface deformation monitoring in permafrost regions of Tibetan Plateau based on ALOS PALSAR data: in ISPRS geospatial week 2017 (Li, D., editor; et al.), The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences = Internationales Archiv für Photogrammetrie, Fernerkundung und Raumbezogene Informationswissenschaften = Archives Internationales des Sciences de la Photogrammétrie, de la Télédétection et de l'Information Spatiale, XLII-2/W7, p. 1509-1512, illus. incl. 2 tables, 8 ref., 2017. Meeting: ISPRS geospatial week 2017, Sept. 18-22, 2017, Wuhan, China.

The permafrost region of Qinghai-Tibet Plateau is widely distributed with the freeze/thaw processes that cause surface structural damage. The differential interferometry synthetic aperture radar (DInSAR) can detect large scale surface deformation with high precision, thus can be used to monitor the freeze/thaw processes of frozen soil area. In this paper, the surface deformation pattern of Qinghai-Tibet railway was analyzed by using the PALSAR 1.0 raw data of the ALOS satellite (L band) and 90 m resolution SRTM DEM data, with the help of two-pass DInSAR method in GAMMA software, and the differential interferograms and deformation maps were obtained accordingly. Besides, the influence of temperature, topography and other factors on deformation of frozen soil were also studied. The following conclusions were obtained: there is a negative correlation between deformation and temperature, and there is a delay between the deformation change and that of temperature; deformation and elevation are positively correlated; the permafrost deformation is also affected by solar radiation that could form variable amplitude variation.

URL: https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-2-W7/1509/2 ...

2018064300 Lebedeva, Liudmila (Melnikov Permafrost Institute, Yakutsk, Russian Federation); Makarieva, Olga; Nesterova, Nataliya; Meyer, Hanno; Efremov, Vladimir and Ogonerov, Vasiliy. Water storages and fluxes within the small watershed in continuous permafrost zone [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10657, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

It is widely accepted that the main source of river runoff in continuous permafrost zone is surface flow and the flow in the seasonally thawing layer. Although the existence of taliks (a layer of year-round unfrozen ground that can be found in permafrost areas) is acknowledged they are usually not considered in the analysis of streamwater sources and in hydrological modelling approaches. The study aims at assessing the possible river sources in small permafrost basin and their contribution to streamflow with special attention to hydrological role of taliks. The study is based on field surveys in 2015 and 2016, the analysis for stable isotopes (dD and d¹⁸O) and the application of a simple mixing model. The Shestakovka River (basin area 170 km²) is a left tributary of the Lena River in the vicinity of Yakutsk city, Eastern Siberia. The climate is dry and continental. Mean air temperature is -9.5°C, precipitation is 240 mm/year, annual runoff depth - 24 mm. Dominant landscapes are pine forest (47% of the watershed area), larch-birch forest (38%) and bogs (14%). Suprapermafrost talik with an area of 58 000 m² was found on the slope covered by the pine forest in 1980s. Field studies showed that the summer flow depth in talik is 60 mm. In 2015 and 2016 264 water samples from river streams, lakes, snow, rain, suprapermafrost groundwater and ground ice were taken in the Shestakovka River watershed and analyzed for stable isotopes composition. Snow has the lightest isotopic composition that varies between -230 and -275 in D and between -30 and - 37 in d18O. Rain water is on average most enriched in D (-70. . . -150 in d18O (-6. . . -19ppm . River water and surface and h h flow in bogs are depleted during snowmelt (April - May) and enriched at the end of the summer. d18O and dD concentrations in lake water vary from -20ppm and -185ppm in snowmelt period to -10ppm and -110ppm in July and August respectively. Suprapermafrost groundwater in two taliks has d18O values between -19ppm and -24ppm dD values between -150ppm and -175ppm. Isotopic concentrations of groundwater are stable through the year. Field surveys and the analysis of isotopic concentrations showed that some surface flow occurs only in bogs. Sub-surface flow forms in larch forests in seasonally thawing layer in July and August. Dry sandy deposits at some slopes in pine forests do not produce surface or shallow subsurface flow but could contain deeper groundwater in taliks. The results of simple two-component mixing model application has shown that in 2015 snowmelt water contributed only 54-70% of streamflow while 30-46% of freshet was supplied by pre-event water. In our opinion suprapermafrost talik water is the most feasible source of the pre-event water. The presence of groundwater in streamflow is indirectly confirmed by the fact that the correlation of total river runoff with last-year precipitation is stronger than with this-year precipitation. It suggests that large and slow water storages in the basins are important chain of hydrological cycle. Taliks could potentially be a significant source for the small rivers in permafrost environments that is not reflected in current process understanding and modelling approaches. The study is partially supported by Russian foundation of basic research, projects No 15-05-08144 and No 16-35-50151. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-10657.pdf

2018064507 McKenzie, Jeffrey M. (McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada) and Siegel, Donald I. Groundwater flow and permafrost thaw; recent advances in numerical modeling in cryohydrogeology [abstr.]: in Geological Society of America, 2017 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 49(6), Abstract no. 126-2, 2017. Meeting: Geological Society of America, 2017 annual meeting & exposition, Oct. 22-25, 2017, Seattle, WA.

Siegel, as my PhD supervisor, provided great mentorship and vision by supporting my initial interests in wanting to study the interactions between groundwater and frozen ground. His support led to a key publication (McKenzie, Voss, Siegel 2007) that provided one of the first numerical groundwater models capable of simulating groundwater flow with dynamic freezing and thawing processes (e.g., variable permeability as a function of ice content, latent heat effects, etc.). The presence of permafrost (i.e. perennially frozen ground) affects the movement and storage of groundwater in cold regions. There are three primary pathways by which groundwater flows in permafrost terrain: 1) above permafrost through the active zone (or supra-permafrost aquifers), 2) below permafrost (i.e., sub-permafrost aquifers), and 3) through taliks, unfrozen vertical or horizontal 'holes' in permafrost. With climate warming and the thawing of permafrost, these pathways become larger and more connected, increasing both the storage and flux of groundwater through the arctic waterscape. Already there is extensive evidence of this hydrologic change, such as increasing flow in arctic rivers, the disappearance or emergence of lakes, and increased carbon export. This presentation will provide an overview of how the model has been recently applied to understanding these hydrologic changes in cryohydrogeology.

2018066436 Mi, S. J. (China Transport Telecommunications & Information Center, Beijing, China); Li, Y. T.; Wang, F.; Li, L.; Ge, Y.; Luo, L.; Zhang, C. L. and Chen, J. B. A research on monitoring surface deformation and relationships with surface parameters in Qinghai Tibetan Plateau permafrost: in ISPRS geospatial week 2017 (Li, D., editor; et al.), The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences = Internationales Archiv für Photogrammetrie, Fernerkundung und Raumbezogene Informationswissenschaften = Archives Internationales des Sciences de la Photogrammétrie, de la Télédétection et de l'Information Spatiale, XLII-2/W7, p. 629-633, illus. incl. 1 table, 9 ref., 2017. Meeting: ISPRS geospatial week 2017, Sept. 18-22, 2017, Wuhan, China.

The Qinghai Tibetan Plateau permafrost has been the largest permafrost region in middle-low latitude in the world for its high altitude. For the large area permafrost, especially surface deformation brought by it, have serious influence on the road engineering, road maintaining and regional economic development. Consequently, it is essential to monitor the surface deformation and study factors that influent it. We monitored an area named Wudaoliang from July 25, 2015 to June 1, 2016 and 15 Sentinel images were obtained during this time. The area we chose is about 35 kilometers long and 2 kilometers wide, and the national road 109 of China passes through the area. The traditional PS-INSAR (Persistent Scatterer Interferometric Synthetic Aperture Radar) method is not suitable because less historical images in the research area and leading to the number of PS (Persistent Scatterer) points is not enough to obtain accurate deformation results. Therefore, in this paper, we used another method which named QUASI-PSInSAR (QUASI Persistent Scatterer Interferometric Synthetic Aperture Radar) to acquire deformation for it has the advantage to weaken or eliminate the effects of spatial and temporal correlation, which has proved by other scholar. After processing 15 images in the SARproz software, we got the conclusions that, 1) the biggest deformation velocity in the whole area was about 127.9 mm/year and about 109.3 mm/year in the road; 2) apparent deformation which have surface deformation more than 30 mm/year was about 1.7 Km in the road. Meanwhile, soil moisture(SM), Land surface temperature (LST) and surface water (SW), which are primary parameters of the land surface over the same time were reversed by using Sentinel data, Landsat data and ZY-3 data, respectively. After analyzing SM, LST , SW and deformation, we obtained that wet areas which had bigger SM, lower LST and more SW, had greater percentage of severe deformation than arid areas; besides, deformation pattern were different in arid areas and wet areas. During the research time, frost heaving firstly accounted for a large proportion both in the arid and wet areas with the decrease of downward radiation from July to December; after December, thaw settlement came into prominence with the increase downward radiation in the arid areas, while in the wet areas, surface put into diverse situations because of water transformation leading to severe deformation. In summary, soil moisture is an important factor that influences the surface deformation. This relationship between deformation process and soil moisture will be researched more in our further work.

URL: https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-2-W7/629/20 ...

2018062392 Patton, Annette I. (Colorado State University, Department of Geosciences, Fort Collins, CO); Rathburn, Sara L.; Capps, Denny M. and Ruleman, Chester A. Preliminary surficial mapping of the Denali National Park and Preserve road corridor; implications for landslide hazards in a changing climate [abstr.]: in Geological Society of America, 2017 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 49(6), Abstract no. 384-5, 2017. Meeting: Geological Society of America, 2017 annual meeting & exposition, Oct. 22-25, 2017, Seattle, WA.

Landslides in Denali National Park and Preserve pose persistent hazards to people and infrastructure. Warming climate and permafrost degradation is likely to increase landslide hazards in this and other high-latitude regions. Increased landslide frequency and magnitude will exacerbate existing challenges to maintaining the Park Road, the sole access to the interior of the park. To better understand the factors that control landslide occurrence in the study region, we are mapping surficial geology of the Park Road corridor. We will delineate all landslides within the map area and characterize the geomorphic conditions at failure sites, including type of failure, underlying lithology, slope parameters, and active layer thickness. Here we present a preliminary map of surficial geology for two reaches along the Park Road at 1:10,000 scale. Bedrock geology is dominated by extrusive lithologies of the Teklanika Volcanics formation; basalt and greenstone of the Nikolai Greenstone formation; sandstone and conglomerate of the Cantwell formation; and unconsolidated Tertiary and Quaternary sedimentary units. Based on initial field work, landslides in these areas appear to occur in altered felsic volcanic rocks where clay layers facilitate sliding, and in unconsolidated units in areas of high relief and/or where the Park Road cuts toe slopes. Additionally, we surveyed two small, active layer detachments on shallow slopes using a terrestrial laser scanner to track downslope movement over time. Future work will evaluate the relationships between landsliding and climate change as expressed via permafrost degradation. To do so, we will evaluate the relationship between depth of the active layer and landslide frequency, quantify the mass of carbon mobilized by small landslides, and conduct a field-based validation of an existing model of permafrost extent within the park.

2018066207 Rawling, J. Elmo, III (Wisconsin Geological and Natural History Survey, Madison, WI); Zoet, Lucas; Attig, John W. and Mode, William N. Geomorphology and Quaternary geology of tunnel channels along the western margin of the Green Bay Lobe, Wisconsin [abstr.]: in Geological Society of America, 2017 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 49(6), Abstract no. 282-1, 2017. Meeting: Geological Society of America, 2017 annual meeting & exposition, Oct. 22-25, 2017, Seattle, WA.

Tunnel channels are common along Marine Isotope Stage 2 (MIS 2) ice marginal landscapes of Wisconsin. Although the geomorphic expression of tunnel channels on the modern landscape varies among former lobes of the Laurentide Ice Sheet, their location is typically marked by linear zones of collapse perpendicular to former ice margins. It is difficult to estimate the size tunnel channels were during formation using their modern surface expression because ice subsequently reoccupied the subglacial tunnel. This was buried by up to ~100 meters of pro and supraglacial sediment, which collapsed several thousand years after ice receded from the area. This poster presents the results of recent geologic mapping and subglacial hydraulic modeling along a portion of the Green Bay Lobe (GBL) in central Wisconsin. Tunnel channels here extend at least 15 km from the Hancock margin, clearly cross the Hancock and Almond margins, and contain kettles that range from ~10 to 40 meters deep. Preliminary results of active and passive seismic surveys indicate the tunnel channels may have reached bedrock up to 100 m below the modern surface. Geologic mapping and Geoprobe coring indicate the upper 20 m of surrounding sediments are predominantly outwash sand and gravel. Previous work along the western margin of the GBL suggested that formation of tunnel channels resulted from the catastrophic discharge of subglacial lakes, tunnel channels may have been active more than once, and permafrost played a key role in the formation of subglacial water ponding that subsequently drained through tunnel channels. However, our modelling of the subglacial hydraulic potential near the margin of the GBL suggests permafrost was not necessary if an adverse bed slope was approximately 11 times greater than the surface slope. This condition occurs at several locations along the western GBL, and in all instances coincident with the presence of tunnel channels. However, there is strong evidence that permafrost was present as ice advanced to the MIS 2 margin, and permafrost must have been present for buried ice to survive through multiple ice advances in the area. In addition, the melting of buried ice produced the geomorphic expression of tunnel channels in the modern landscape. Therefore, the geomorphic record of the area can provide insight into subglacial processes.

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