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2023003332 Akhtar, Sharmin (University of Manitoba, Department of Civil Engineering, Winnipeg, MB, Canada); Hollaender, Hartmut and Yuan, Qiuyan. Impact of heat and contaminants transfer from landfills to permafrost subgrade in Arctic climate; a review: Cold Regions Science and Technology, 206, Article no. 103737, 146 ref., February 2023. Based on Publisher-supplied data.
Permafrost, a common phenomenon found in most Arctic regions, is undergoing vulnerability due to climatic changes and improper waste management. Landfilling is the traditional household, industrial, and commercial solid waste disposal method. Leachate, heat, and gas are the primary byproducts of waste degradation in landfills and can threaten the environment and human health and induce climate change by polluting the soil, groundwater, and air. This review aims to summarize the available literature and identify knowledge gaps in understanding heat transfer, permafrost melt, and leachate seepage mechanisms in the landfill environment. Research showed that engineered landfills are affected by their generated heat which is one of the primary byproducts of landfills. Excessive heat in the landfill can create cracks in the liners and covers, thereby decreasing the lifecycle of the landfill barriers and polluting soil and groundwater. The contaminated groundwater flow thereby creates unsafe conditions for humans and the environment. The article also shows that building a landfill in permafrost regions is concerning because the excess heat generated may transfer to the permafrost ground layer via conduction and cause permafrost degradation. Permafrost thawing can increase the water content in the ground, leading to soil erosion, and settlement, accelerating the permafrost carbon cycle and releasing greenhouse gases into the atmosphere resulting in climate change. The article indicates that landfill gas production is another reason for increased levels of global warming.
DOI: 10.1016/j.coldregions.2022.103737
2023003327 Huang Shuai (Heilongjiang University, School of Civil Engineering, Harbin, China); Ding Qian; Chen Kezheng; Hu Zheng; Liu Yanjie; Zhang Xiaodong; Gao Kai; Qiu Kaichi; Yang Yang and Ding Lin. Changes in near-surface permafrost temperature and active layer thickness in northeast China in 1961-2020 based on GIPL model: Cold Regions Science and Technology, 206, Article no. 103709, illus., 68 ref., February 2023. Based on Publisher-supplied data.
Characteristics of active layer processes depend on the conditions of the ground surface, coupled water-heat balance, soil hydrology, and soil properties under frozen and thawed states at shallow depths. Mean annual temperature at the bottom of the active layer (MATBAL) and active layer thickness (ALT) are important metrics in studying the features of active layer processes and the thermal stability of permafrost. Affected by the changing climate, permafrost regions in Northeast China have undergone remarkable changes in the past 30 years, many of which are still ongoing. In Northeast China, however, model studies on examining hydrothermal dynamics and on changes in frozen ground have faced serious challenges, including a complex ecological environment and rugged terrains. In this study, the Geophysical Institute Permafrost Lab (GIPL) model was used to map temporal and spatial variations in MATBAL and ALT in Northeast China, where discontinuous, island, and sporadic permafrost coexists with seasonal frost. Using the parameters of ground surface temperature (GST) and soil properties as input, we applied the GIPL model to analyze the distributive characteristics of near-surface permafrost in Northeast China. The results indicate a sharply shrinking permafrost area from 5.49´105 to 2.29´105 km2 but rapidly rising rates of 0.17-0.83°C/decade in MATBAL in Northeast China during the period from 1961 to 2020. Under a persistently warming climate, accelerating permafrost degradation will inevitably affect the hydrological environment, boreal ecosystem, soil biology, and engineering infrastructure. This work fills a gap in the distribution of MATBAL and ALT in Northeast China.
DOI: 10.1016/j.coldregions.2022.103709
2023003341 Pan Jingjing (Jilin University, College of Construction Engineering, Changchun, China); Wang Boxin; Wang Qing; Ling Xianzhang; Liu Jiaqi; Fang Ruichang and Wang Zihao. Deformation characteristics of the shear band of silty clay-concrete interface under the influence of freeze-thaw: Cold Regions Science and Technology, 206, Aritcle no. 103750, 50 ref., February 2023. Based on Publisher-supplied data.
Direct shear tests of the silty clay-concrete interface under different moisture contents and freeze-thaw (F-T) cycles were conducted to study the mechanical and deformation characteristics of the silty clay-concrete interface under the action of F-T cycles. The change rule of shear band thickness under F-T cycles were analyzed based on particle image velocimetry technology. The microstructure changes of the damaged specimens were observed combined with scanning electron microscopy. Experimental results show that the shear strength of the silty clay-concrete interface is negatively correlated with the F-T cycles and moisture content. The moisture content increases from 12.7% to 20.7%, and the shear strength of the shear band decreases by 7.6%, 7.5%, 7.5%, 12.3%, and 10.5% after 9 F-T cycles, respectively. The shear strength of the shear band decreases obviously after 3 F-T cycles, and tends to be stable after 7 F-T cycles. The successive F-T cycles increases the thickness of the shear band until it stabilizes after 3 F-T cycles. The length and width of cracks inside the specimen increase as the number of F-T cycles rises. The orientation of particles in the shear band is weakened, but the orientation of particles in the shear band is always stronger than that outside the shear band. The change in soil particle and pore content is the most obvious in 3 F-T cycles, and it is the reason for the change in shear band.
DOI: 10.1016/j.coldregions.2022.103750
2023003338 Qin Yinghong (Guangxi University, College of Civil Engineering and Architecture, Nanning, China); Wang Tianyu and Qin Menglin. Thermal storage under an earthen roadway embankment over a permafrost region: Cold Regions Science and Technology, 206, Article no. 103745, 21 ref., February 2023. Based on Publisher-supplied data.
Building roadways in permafrost regions is always challenged because both roadway construction and global warming can induce the warming of the underlying soils. A group of permafrost cooling techniques has been employed to cool the embankment, with the focus on dropping the temperature of the underlying permafrost. To this end, understanding the thermal storage in the underlying soils after the embankment construction is critical to adopt the right techniques to drain the soils' heat at the right place. While the non-linear variation of heat absorption with depth in the permafrost under the embankment has been well documented, it remains unknown how to describe this situation mathematically. In this study, we innovatively propose a scalar DE to characterize the thermal storage of the soils under an earthen embankment over a permafrost region. It is found that immediately after the embankment was built, the soils at 0-3 m depth are cooled down while those at 3-6 m depth are warmed up. However, the temperature variations of these soils, in shape and in trend, are different from the thermal storage of the soils. The profile of temperature variation versus depth changes continuously, while the profile of thermal storage versus depth varies abruptly at the interfaces of soil layers. The reason is that most heat entering the permafrost stratum is stored in water-rich soils while a limited heat is deposited in water-poor soils. This finding suggests that permafrost cooling techniques shall be considered to drain the thermal storage in the water-rich soils primarily.
DOI: 10.1016/j.coldregions.2022.103745
2023003330 Tang Liyun (Xi'an University of Science and Technology, School of Architecture and Civil Engineering, Xi'an, China); Cui Yupeng; Chen Jianbing; Yang Gengshe; Sun Shiyuan; Li Guoyu; Sun Qiang and Jia Hailiang. Analysis and research on the difference of design codes for vertical bearing capacity of pile foundation in cold regions: Cold Regions Science and Technology, 206, Article no. 103723, 107 ref., February 2023. Based on Publisher-supplied data.
The design results of pile foundations based on different national codes are not identical owing to differences in the design and calculation of the vertical bearing capacity of frozen soil pile foundation, thus inconveniencing pile foundation designers involved in international projects. This paper summarises the distribution of large-scale projects and the selection of pile foundations in cold regions. Models of a frictional elastic system and a friction end-bearing rigid-elastic system were obtained based on the vertical force characteristics of pile foundations under climate change in cold region. Differences in the design and calculation methods of the vertical bearing capacity of the pile foundations and the determination methods of the vertical ultimate bearing capacity in construction, transportation, and power transmission engineering in cold regions of various countries were discussed, and the applicability of each design method under complicated conditions was proposed. The calculations of the end resistance, side resistance, negative friction and frost heaving force of pile foundations in different national codes were described, and the values of partial safety factor for resistance and factor of safety were discussed, and the basis for the selection is summarised for different engineering design parameters. The study is intended to provide essential normative guidance for designing the vertical bearing capacity for pile foundation engineering in cold regions.
DOI: 10.1016/j.coldregions.2022.103723
2023003342 Wang Fei (Jiangsu University, Faculty of Civil Engineering and Mechanics, Zhenjiang, China); Li Guoyu; Ma Wei; Chen Dun; Wu Gang; Cao Yapeng; Mu Yanhu; Mao Yuncheng; Zhang Jun; Gao Kai; Wang Xinbin; Jing Hongyuan and Che Fuqiang. Assessment of permafrost disturbances caused by two parallel buried warm-oil pipelines; a case study at a high-latitude wetland site in northeast China: Cold Regions Science and Technology, 206, Article no. 103753, 38 ref., February 2023. Based on Publisher-supplied data.
Multiple studies demonstrate that narrow-linear strong disturbances triggered by pipeline engineering activities have resulted in rapid permafrost degradation. However, the extent, duration, and severity of permafrost disturbances induced by two parallel buried warm-oil pipelines remain unclear. Here, we examine the thermal disturbances of the China-Russia crude oil pipelines (CRCOPs I and II) on the surrounding permafrost. Ground temperature measurements on and off the right-of-way of the CRCOPs and an electrical resistivity tomography survey were conducted at a selected high-latitude wetland site in northeastern China. The observations showed that warm oil flow in pipelines dissipated heat to the surrounding soil, resulting in the thawing of underlying permafrost accompanied by the formation and development of thaw bulbs around the pipes. Currently, the thaw bulb of CRCOP-I was about four times as large as that of CRCOP-II, mainly due to the longer 7-year working duration of CRCOP-I. To quantify the permafrost disturbances around the pipeline, a conductive heat transfer model was established. A numerical simulation of the soil thermal regime around the pipeline suggested the initial growth of the thaw bulb was quite fast but gradually slowed with time, of which the shape was modified to ellipse from a semicircle. The existence of CRCOP-II would accelerate the warming of permafrost on the CRCOP-I right-of-way due to the small separation distance between them. We expect that the thaw bulbs of the two pipelines will expand larger than previously estimated due to the adverse effects of pipeline settlement and surface water flow, sparking a wider permafrost disturbance.
DOI: 10.1016/j.coldregions.2022.103753
2023003331 Wu, Hanli (Missouri University of Science and Technology, Department of Civil, Architectural, and Environmental Engineering, Rolla, MO); Zhang, Xiong and Liu, Jenny. Thermal performance analysis of hollow cellular concrete block air convection embankment for cold regions: Cold Regions Science and Technology, 206, Article no. 103733, 35 ref., February 2023. Based on Publisher-supplied data.
Crushed-rock air convection embankment (ACE) is an excellent passive cooling technique that uses open-graded crushed rocks as a "thermal semi-conductor" to prevent roadbeds from thawing in summer and enhance the cooling effect in winter in permafrost regions. However, the desired crushed rocks needed for ACE are not readily available in interior Alaska, resulting in extremely high construction costs. Previous studies indicated that using the cost-effective cellular concrete for ACE could effectively enhance the cooling performance of ACE and mitigate moisture warping and temperature curling of the asphalt concrete layer. It is promising to be an alternative to crushed rocks for ACE to mitigate pavement distresses. However, the design of cellular concrete ACE needs to be further studied to maximize performance and facilitate future implementation. Hence, two design configurations of cellular concrete block ACEs were proposed in this study. The thermal performance of pavement structures with these two designs was investigated by comparing them with the other four. A total of six pavement structures were analyzed, including a typical flexible pavement in the Northern Region of Alaska and five pavement structures reinforced with different paving interlayers, i.e., silty sand/gravel, crushed rocks, cast-in-place cellular concrete (full insulation), and two types of precast cellular concrete blocks. The thermal profiles, air pressure gradients, and velocities were numerically analyzed in ANSYS Fluent. The numerical results indicated that the two proposed cellular concrete ACEs exhibited a significant heat insulation effect in summer and a desired cooling effect in winter, which raised the permafrost table significantly. The maximum thaw depth of the two proposed cellular concrete ACEs was only 15% of the thaw depth of traditional silty sand/gravel embankment.
DOI: 10.1016/j.coldregions.2022.103733
2023003328 Zhao Yanhu (Chang'an University, School of Highway, Xi'an, China); Zhang Mingyi and Gao Juan. Research progress of constitutive models of frozen soils; a review: Cold Regions Science and Technology, 206, Article no. 103720, 70 ref., February 2023. Based on Publisher-supplied data.
In the past more than half a century, the constitutive models for geomaterials have been widely flourished. With the rapid development of economic, engineering infrastructures are booming in cold regions, including tunnels, highways, and so on. Besides, artificial freezing is used to solve the water-rich soft ground problem during the excavation of mines or tunnels. Building a highly applicable constitutive model of frozen soil will be helpful for the engineering practices where frozen soil is involved. Due to the existence of ice in soil matrix, there is a great difference in the mechanical behaviors of frozen soil and unfrozen soil. Correspondingly, it is more complicated to establish the constitutive model of frozen soil than that of unfrozen soil. So far, a great number of constitutive models of frozen soil based on different theories have been proposed. In this paper, firstly, the generally recognized basic mechanical properties of frozen soil are introduced. Secondly, the authors summarized various kinds of constitutive models of frozen soils, and analyzed their properties comprehensively. Finally, future research tends for constitutive models of frozen soil are proposed.
DOI: 10.1016/j.coldregions.2022.103720
2023003339 Zhou Yalong (Lanzhou Jiaotong University, School of Civil Engineering, Lanzhou, China); Wang Xu; He Fei; Hu Yuan; Niu Fujun; Guo Chunxiang and Jiang Daijun. Calculation method and model tests of pile frost jacking for railway overhead contact systems in permafrost regions: Cold Regions Science and Technology, 206, Article no. 103746, 45 ref., February 2023. Based on Publisher-supplied data.
One of the major challenges encountered in electrification reconstruction project of Golmud-Lhasa section of Qinghai-Tibet railway of China is ensuring the frost jacking stability of the pile foundation of overhead contact system mast (OCSM). To evaluate the resisting frost jacking performance of OCSM pile in permafrost regions, a theoretical model of OCSM pile in permafrost soils under the effect of frost heave was constructed based on superposition principle and deformation coordination relationship between the pile and soil. The model was solved by using the finite difference method combined with MATLAB. Then, large scale model tests were performed to investigate the thermodynamic behaviors of OCSM piles with different sections (equal section circular pile, straight cone cylindrical pile and curved cone cylindrical pile) in the permafrost soils under freeze-thaw actions, after which the theoretical model were validated. It was found that distribution curves of pile axial force obtained by the calculation method is basically consistent with model test results in the overall trend, implying that the calculation model is reasonable and feasible. During soil freezing, the pile is under tension as a whole, and the axial force is greatest near the depth of frost penetration. The maximum value of tangential frost-heave stress occurs near the ground surface. The total tangential frost heaving force of the curved cone cylindrical pile is the smallest, and the effect of resisting frost jacking is the best. These research results can provide a reference for resisting frost jacking design of OCSM pile in permafrost regions.
DOI: 10.1016/j.coldregions.2022.103746
2023000659 Dzhurik, V. I. (Russian Academy of Sciences, Siberian Branch, Institute of the Earth's Crust, Irkutsk, Russian Federation); Bryzhak, E. V.; Batsayhan, Ts. and Serebrennikov, S. P. Predicting dynamic effects of large earthquakes in areas of degrading permafrost (Baikal-Mongolia region): Russian Geology and Geophysics, Pre-Issue Publication, illus. incl. 1 table, geol. sketch maps, 28 ref., December 5, 2022.
The study addresses basic problems of modern geodynamics and seismicity of the Central Asian lithosphere. It aims at predicting dynamic effects of large earthquakes for seismic safety of the Baikal-Mongolian region. Special focus is made on the seismic behavior of areas where seismic risk zoning is problematic because of permafrost. The paper presents synthesis of previous and new data on ground responses to large earthquakes in specific territories of the Baikal-Mongolia region with complex cryological conditions. The results include shaking intensity patterns and predicted seismic parameter values for degraded permafrost in zones of different climates and seismicity levels. The obtained prediction maps can make reference in studies of variable permafrost responses to temperature, seismic, and mining-related impacts.
DOI: 10.2113/RGG20224478
2023005895 Luo Jing (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Niu Fujun; Lin Zhanju; Liu Minghao; Yin Guoan and Gao Zeyong. Inventory and frequency of retrogressive thaw slumps in permafrost region of the Qinghai-Tibet Plateau: Geophysical Research Letters, 49(23), Article e2022GL099829, illus. incl. sketch map, 45 ref., December 16, 2022.
Due to the increasing air temperatures, retrogressive thaw slumps (RTSs) have become more common on the Qinghai-Tibet Plateau (QTP), but their inventory, frequency, and initiation have not been fully investigated. In satellite imagery for the period 2018-2020, 2669 active RTSs were identified in permafrost regions of the QTP. Most of the RTSs occur in regions with elevations ranging from 4,600 to 5,100 m along north-facing slopes varying from 3° to 8°. The number of RTSs and their affected areas increased by 4 and 6 times, respectively, in three densely distributed RTS regions from 2008/2013 to 2021. This increase in the RTS occurrence mainly occurred during the warm season in 2010 and 2016 and is likely due to high air temperatures during the thawing season, which induced the massive occurrence of active-layer detachment slides. Another intensification of RTS occurrences may appear when higher anomaly air temperatures are observed. Abstract Copyright (2022), The Authors.
DOI: 10.1029/2022GL099829
2023005951 McSweeney, Killian (University of Georgia, Department of Geography, Athens, GA) and Kooperman, Gabriel J. Consistent timing of Arctic permafrost loss across the CESM1 large ensemble: Geophysical Research Letters, 49(24), Article e2022GL100864, illus. incl. sketch map, 33 ref., December 28, 2022.
The Arctic is especially vulnerable to climate change and is warming faster than the global average. Changes in this region pose a heightened threat due to the immense amount of carbon frozen as organic material in the soil. When permafrost thaws, organic material decays and releases as greenhouse gases into the atmosphere, contributing to further warming. A better understanding of the processes that influence permafrost degradation is needed to inform climate adaptation and mitigation planning. This study assesses changes to Arctic permafrost across 35 ensemble member simulations from the Community Earth System Model 1 Large Ensemble Project, under the Representative Concentration Pathway 8.5 21st century scenario. Most Arctic near-surface permafrost is lost by 2100, but timing varies across regions and with soil depth. Internal climate variability, represented by differences between ensemble members, has a constrained influence on degradation timing due to relative consistency of summer temperature increases and insulation by winter snow cover. Abstract Copyright (2022), The Authors.
DOI: 10.1029/2022GL100864
2023000663 Nikitenko, M. N. (Russian Academy of Sciences, Siberian Branch, Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, Russian Federation); Glinskikh, V. N.; Mikhaylov, I. V. and Fedoseev, A. A. Mathematical modeling of transient electromagnetic sounding signals for monitoring the state of permafrost: Russian Geology and Geophysics, Pre-Issue Publication, illus., 20 ref., December 6, 2022.
The study is aimed at theoretical development and scientific substantiation of a high-resolution transient electromagnetic (TEM) geophysical technique for monitoring the state of permafrost. The electromagnetic monitoring configuration includes spatially distributed sounding systems for surface and borehole locations of the field sources and receivers. Changes in the electrophysical properties of the earth can be traced for the cases of both ground thawing and freezing. We developed the theory of TEM signals modeling, upon which created an algorithm for rapid and accurate numerical simulation of the electromagnetic field. The signals are scrutinized from the various sounding systems in the basic earth models as function of registration time. We show how the features associated with a spatial arrangement of frozen rocks appear on the EMF diagrams. It follows that a set of the measured data enables visual detection of the boundary between frozen and thawed rocks.
DOI: 10.2113/RGG20224514
2023004490 Reyes, Alberto V. (University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada); Jensen, Britta J. L.; Woudstra, Shaun H.; Bolton, Matthew S. M.; Buryak, Serhiy D.; Cook, Mea S.; Harvey, Jordan and Westgate, John A. Detrital glass in a Bering Sea sediment core yields a ca, 160 ka Marine Isotope Stage 6 age for Old Crow Tephra: Geology (Boulder), 51(1), p. 106-110, illus. incl. sketch map, 33 ref., December 2, 2022.
For decades, the Old Crow tephra has been a prominent stratigraphic marker for the onset of Marine Isotope Stage (MIS) 5e, the last interglaciation, in subarctic northwest North America. However, new zircon U-Pb dates for the tephra suggest that the tephra was deposited ca. 207 ka during MIS 7, with wide-ranging implications for chronologies of glaciation, paleoclimate, relict permafrost, and phylogeography. We analyzed ~1900 detrital glass shards from 28 samples collected at Integrated Ocean Drilling Program Site U1345 in the Bering Sea, which has a well-constrained age model from benthic foraminiferal d18O. Except for one possibly contaminant shard dated at 165 ka, Old Crow tephra was absent from all samples spanning 220-160 ka. Old Crow tephra appeared abruptly at 157 ka, comprising >40% of detrital shards between 157 and 142 ka. This abrupt increase in the concentration of detrital Old Crow tephra, its absence in earlier intervals, and its presence at low concentrations in all samples between 134 and 15 ka collectively indicate that the tephra was deposited during the middle of MIS 6 with a likely age of 159±8 ka. As a result, the late Quaternary chronostratigraphic framework for unglaciated northwest North America remains intact, and the timing of key events in the region (e.g., bison entry into North America; interglacial paleoclimate; permafrost history; the penultimate glaciation) does not require wholesale revision.
DOI: 10.1130/G50491.1
2023005966 Young, Joseph M. (University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada); Alvarez, Alejandro; Sluijs, Jurjen; Kokelj, Steven V.; Rudy, Ashley; McPhee, Alex; Stoker, Benjamin J.; Margold, Martin and Froese, Duane. Recent intensification (2004-2020) of permafrost mass-wasting in the central Mackenzie Valley foothills is a legacy of past forest fire disturbances: Geophysical Research Letters, 49(24), Article e2022GL100559, illus. incl. sketch map, 58 ref., December 28, 2022.
The effects of recent climate change are accelerating permafrost thaw, including ice-rich landscapes of the western Canadian Arctic. However, regional drivers of permafrost slope failure in hillslopes with warm, thin permafrost remain poorly understood. Repeat satellite imagery (1984-2020) indicates rapid increases in retrogressive thaw slumps (RTSs) and deep-seated permafrost landslides (DSPLs) since 2004, indicating a change in slope stability thresholds in an area that otherwise appeared thaw stable. The widespread occurrence of DSPL represents a contrasting geomorphic response to the RTS-dominated ice-rich permafrost landscapes. In this study area, RTS and DSPL occur predominantly in areas that were burned by forest fires in the 1990s, indicating a legacy thermal disturbance that preconditioned permafrost hillslopes for failure. The relations between historic fires and the later development of widespread permafrost slope failures represent an outstanding example of the complex interactions between inherited landscape sensitivity in ice-rich terrain and ongoing climate change. Abstract Copyright (2022), The Authors.
DOI: 10.1029/2022GL100559
2023006088 Forbes, Donald L. (Natural Resources Canada, Geological Survey of Canada, Dartmouth, NS, Canada); Craymer, M. R.; James, T. S. and Whalen, Dustin. Subsidence drives habitat loss in a large permafrost delta, Mackenzie River outlet to the Beaufort Sea, western Arctic Canada: in Landscape and seascape responses to Canada's changing climate (James, Thomas S., editor; et al.), Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 59(11), p. 914-934 (French sum.), illus. incl. 4 tables, sketch maps, 103 ref., November 2022.
The Mackenzie Delta is an extensive river-mouth depocentre, the second largest delta on the Arctic Ocean, and lies in the zone of continuous permafrost. We report the first measurements of natural consolidation subsidence in a high-latitude delta with ice-bonded sediments. Several years of episodic GPS records on a network of 15 stable monuments throughout the central and outer delta reveal downward motion between 1.5 ± 0.7 and 5.3 ± 1.1 mm/year relative to a nearby monument on bedrock. Additional shallow subsidence results from loss of near-surface excess ice with deeper seasonal thaw in a warming climate. Isostatic adjustment is a third component of subsidence, captured in the NAD83v70VG crustal velocity model. Sedimentation rates over much of the outer delta are less than the rate of subsidence combined with rising sea level. Scenarios for future inundation are evaluated using interpolated IPCC AR5 projections, NAD83v70VG, and a LiDAR DEM with realistic consolidation, thaw subsidence, and sedimentation rates, on time scales of 40 and 90 years. These reveal increases in area flooded at mean water level from 33% in 2010 to 65% or as much as 85% in 2100, depending on the emissions scenario, driving delta-front retreat and removing a large proportion of avian nesting habitat. The three components of subsidence together increase the relative sea-level rise by a factor of two to eight, depending on the scenario. Consolidation subsidence may also contribute to rising low-flow water levels in the central delta, increasing river-lake connectivity, with negative impacts on aquatic biodiversity and productivity.
DOI: 10.1139/cjes-2021-0127
2023006091 Malenfant, François (Saint Mary's University, Department of Geography and Environmental Studies, Halifax, NS, Canada); Whalen, Dustin; Fraser, P. and Van Proosdij, D. Rapid coastal erosion of ice-bonded deposits on Pelly Island, southeastern Beaufort Sea, Inuvialuit Settlement region, western Canadian Arctic: in Landscape and seascape responses to Canada's changing climate (James, Thomas S., editor; et al.), Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 59(11), p. 961-972 (French sum.), illus. incl. sect., 7 tables, geol. sketch maps, 37 ref., November 2022.
This paper quantifies rates of shoreline change and investigates the influence of surficial geology on shoreline dynamics between 1950 and 2018 on Pelly Island, located 10 km off the Mackenzie Delta. Long-term changes in shoreline position were calculated using imagery analysis and Analysing Moving Boundaries Using R (AMBUR). The influence of shoreline exposure to predominant storm direction and influence of surficial geology were examined for northwestern and southeastern zones. The average annual linear regression rate (LRR) rate during the 1950-2018 observation period was -3.8 m·a-1. The end point rate (EPR) was calculated for seven observation periods: 1950-1972, 1972-1985, 1985-2000, 2000-2018, 2000-2013, 2013-2018, and 1950-2018. A mean EPR of -5.5 ± 0.7 m·a-1 was calculated for the 2000-2018 period, and a maximum retreat rate of 46.7 ± 2.1 m·a-1 was recorded during the 2013-2018 observation period. By comparing the rate of change for sections of historical shorelines with differing surficial geology and exposure to storms, it was possible to draw conclusions on why Pelly Island continues to have the highest retreat rates in the Mackenzie-Beaufort region. Greater retreat rates were observed in lacustrine deposits (5.3 m·a-1) compared with moraine deposits (2.7 m·a-1). In addition, shoreline exposure to the predominant storm direction from the northwest was found to be a major influence on rates of shoreline change in all observation periods.
DOI: 10.1139/cjes-2021-0118
2023006087 Oldenborger, Greg A. (Natural Resources Canada, Geological Survey of Canada, Ottawa, ON, Canada); Short, Naomi and LeBlanc, Anne-Marie. Permafrost thaw sensitivity prediction using surficial geology, topography, and remote-sensing imagery; a data-driven neural network approach: in Landscape and seascape responses to Canada's changing climate (James, Thomas S., editor; et al.), Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 59(11), p. 897-913 (French sum.), illus. incl. 5 tables, geol. sketch maps, 75 ref., November 2022.
Seasonal or degradational thaw subsidence of permafrost terrain affects the landscape, hydrology, and sustainability of permafrost as an engineering substrate. We perform permafrost thaw sensitivity prediction via supervised classification of a feature set consisting of geological, topographic, and multispectral variables over continuous permafrost near Rankin Inlet, Nunavut, Canada. We build a reference classification of thaw sensitivity using process-based categorization of seasonal subsidence as measured from differential interferometric synthetic aperture radar whereby categories of thaw sensitivity are reflective of ground ice conditions. Classification is performed using a neural network trained on both dispersed and parcel-based reference data. For Low, Medium, High, and Very High thaw sensitivity categories, generalized classification accuracy is 70.8% for 20.6 km2 of dispersed training data. In all cases, the majority classes of Low and Medium thaw sensitivity are predicted with higher accuracy and more certainty, while the minority classes of High and Very High thaw sensitivity are underpredicted. Minority classes can be combined to improve accuracy at the expense of a reduced level of discrimination. The two-class problem can be classified with an accuracy of 81.8%, thereby effectively distinguishing between stable and unstable ground. The method is applicable to similar Low-Arctic permafrost terrain with geological and topographical controls on thaw sensitivity. However, generalized accuracy is reduced for parcel-based training, indicating that reference samples are not totally representative for inference beyond the parcel, and any deployment of the network to other geographical regions would benefit from full or partial retraining with local data.
DOI: 10.1139/cjes-2021-0117
2023006078 Paquette, Michel (Queen's University, Department of Geography and Planning, Kingston, ON, Canada); Fortier, Daniel and Lamoureux, Scott F. Cryostratigraphical studies of ground ice formation and distribution in a High Arctic polar desert landscape, Resolute Bay, Nunavut: in Landscape and seascape responses to Canada's changing climate (James, Thomas S., editor; et al.), Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 59(11), p. 759-771 (French sum.), illus. incl. strat. cols., 3 tables, sketch map, 73 ref., November 2022.
Ground ice distribution and abundance have wide-ranging effects on periglacial environments and possible impacts on climate change scenarios. In contrast, very few studies measure ground ice in the High Arctic, especially in polar deserts and where coarse surficial material complicates coring operations. Ground ice volumes and cryostructures were determined for eight sites in a polar desert, near Resolute Bay, Nunavut, chosen for their hydrogeomorphic classification. Dry, unvegetated polar desert sites exhibited ice content close to soil porosity, with a <45 cm thick ice-enriched transition zone. In wetland sites, suspended cryostructures and ice dominated cryofacies (ice content at least 2´ soil porosity values) were prevalent in the upper ~2 m of permafrost. Average ground ice saturation at those locations exceeded porosity values by a factor between 1.8 and 20.1 and by up to two orders of magnitude at the ~10 cm vertical scale. Sites with the highest ice contents were historically submerged wetlands with a history of sediment supply, sustained water availability, and syngenetic and quasi-syngenetic permafrost aggradation. Ice enrichment in those environments were mainly caused by the strong upward freezing potential beneath the thaw front, which, combined with abundant water supply, caused ice aggradation and frost heaving to form lithalsa plateaus. Most of the sites already expressed cryostratigraphic evidence of permafrost degradation. Permafrost degradation carries important ecological ramifications, as wetland locations are the most productive, life-supporting oases in the otherwise relatively barren landscape, carrying essential functions linked with hydrological processes and nutrient and contaminant cycling.
DOI: 10.1139/cjes-2020-0134
2023005464 Varsadiya, Milan (University of South Bohemia, Department of Ecosystems Biology, Ceske Budejovice, Czech Republic); Liebmann, Patrick; Petters, Sebastian; Hugelius, Gustaf; Urich, Tim; Guggenberger, Georg and Barta, Jiri. Extracellular enzyme ratios reveal locality and horizon-specific carbon, nitrogen, and phosphorus limitations in Arctic permafrost soils: Biogeochemistry (Dordrecht), 161(2), p. 101-117, illus. incl. 2 tables, 62 ref., November 2022.
Permafrost affected soils are highly vulnerable to climate change. These soils store huge amounts of organic carbon (C), and a significant proportion of this carbon is stored in subsoil horizons where it might become available to microbial decomposition under global warming. An important factor in understanding and quantifying the C release from soils include the limitation of resources for microbes. Microbes decompose soil organic matter (SOM) by secreting extracellular enzymes into the soil, thus enzyme activity and their ratios are considered important indicators of soil nutrient availability and microbial substrate limitation. To evaluate nutrient limitation and the limitation of microbial substrate utilization, we investigated the potential enzyme activity from whole soil profiles, including topsoil, cryoturbated organic matter, mineral subsoil, and permafrost of Herschel Island (Canada) and Disko Island (Greenland). We included seven enzymes (five hydrolytic and two oxidative) and related them to bacterial and fungal gene abundance. The results showed hydrolytic enzymatic activity was strongly influenced by soil type, whereas oxidative enzymes varied between different localities. The enzyme ratios indicated that the topsoil microbial communities were C and phosphorus (P) co-limited in both localities, whereas the subsoil communities were nitrogen (N) limited from HI and C, P limited from DI. A strong positive correlation between all measured enzymes and bacterial gene abundance compared to that of fungi suggested that bacteria might play a more important role in SOM decomposition in permafrost soil horizons. This study suggests that Arctic permafrost microbial communities were not only limited by N, but also by C, P, and their co-limitation under specific conditions (i.e., higher abundance of bacteria and lower abundance of fungi).
DOI: 10.1007/s10533-022-00967-z
2023006090 Whalen, Dustin (Natural Resources Canada, Geological Survey of Canada, Dartmouth, NS, Canada); Forbes, Donald L.; Kostylev, V.; Lim, M.; Fraser, P.; Nedimovic, M. R. and Stuckey, S. Mechanisms, volumetric assessment, and prognosis for rapid coastal erosion of Tuktoyaktuk Island, an important natural barrier for the harbour and community: in Landscape and seascape responses to Canada's changing climate (James, Thomas S., editor; et al.), Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 59(11), p. 945-960 (French sum.), illus. incl. sect., 3 tables, geol. sketch maps, 103 ref., November 2022.
The coastline of the Inuvialuit Settlement Region (ISR) in the Mackenzie-Beaufort region of the western Canadian Arctic is characterised by rapid erosion of ice-bonded sediments with abundant excess ground ice, resulting in widespread thermal and mechanical process interactions in the shore zone. Coastal communities within the ISR are acutely aware of the rapidly eroding coastline and its impacts on infrastructure, subsistence activities, cultural or ancestral sites, and natural habitats. Tuktoyaktuk Island is a large natural barrier protecting the harbour and surrounding community from exposure to waves. It is threatened by coastal erosion, a better understanding of which will inform adaptation strategies. Using historical and recent aerial imagery, high-resolution digital elevation models, cliff geomorphology, stratigraphy, and sedimentology, including ground-ice content, this study documents erosional processes, recession rates, volume losses, and sediment delivery since 1947 and projected into the future. Erosion along the northwest-facing (exposed) cliff, primarily by thermo-abrasional undercutting and block failure, has accelerated since 2000 to a mean of 1.80 ± 0.02 m/year, a 22% increase over the previous 15 years and 14% faster than 1947-2000. Lower recession rates on the harbour side of the island increased more than two-fold. Projection of future shoreline vectors by extrapolation, using the post-2000 accelerated coastal recession rates at 284 transects, points to breaching of this vital natural harbour barrier by 2044, after which rapid realignment is expected to occur as the new inlet evolves. Further acceleration of rates, as seems highly likely, brings the breaching date closer.
DOI: 10.1139/cjes-2021-0101
2023001417 Jacquemart, Mylène (Eidgenössische Technische Hochschule Zurich, Laboratory for Hydraulics, Hydrology, and Glaciology, Zurich, Switzerland); Welty, Ethan; Leopold, Matthias; Loso, Michael; Lajoie, Lia and Tiampo, Kristy. Geomorphic and sedimentary signatures of catastrophic glacier detachments; a first assessment from Flat Creek, Alaska: Geomorphology, 414, Article 108376, illus. incl. 2 tables, geol. sketch maps, 78 ref., October 1, 2022. Includes appendices.
Large-volume detachments of low-angle mountain glaciers involve the sudden mobilization of large amounts of glacier ice and lithic material in long-runout mass flows. Scientific investigations of these events have only recently brought to light their global occurrence and the similarities in the conditions under which they occur. While this recent research suggests that glacier detachments may become more frequent in a warming climate, a long-term record is largely lacking. Knowledge of the geomorphic signatures of glacier detachments could help establish such a record. Here, we present the first geomorphic and sedimentary assessment of a glacier detachment deposit. We investigate the landscape impacts of the Flat Creek glacier detachments in Alaska's St. Elias mountains through a combination of remote sensing analyses, field observations, Electrical Resistivity Tomography, and grain size and grain orientation analyses. From these data, we outline a land-system model that may help identify past glacier detachments elsewhere. Some of the most distinguishing features we documented were large bodies of buried ice-conglomerates, a rapid response of the remnant glacier ice, clusters of small-scale thermokarst ponds, countless molards, parallel striations etched into the hillslope and individual clasts, and a very long runout distance. We assess these features in terms of their longevity in the landscape and compare them to what has been described at glacier detachment sites elsewhere. Finally, we discuss to what extent glacier detachment deposits can be distinguished from deposits left by rock(-ice) avalanches, debris flows, and surging glaciers, and show that a differentiation is possible if detailed field investigations are undertaken.
DOI: 10.1016/j.geomorph.2022.108376
2023005455 Kovda, I. V. (Dokuchaev Soil Science Institute, Moscow, Russian Federation). Common features in Cryosols and Vertisols at the macro- and microlevels: Eurasian Soil Science, 55(10), p. 1335-1347, illus. incl. 3 tables, 60 ref., October 2022.
The central images and main areas of Vertisols and Cryosols differ greatly. However, in recent years, Vertisols have been found in the permafrost area, and in some paleosols, both paleocryogenic and vertic features have been noted. In this regard, the study of common features and differences at different levels of organization of Cryosols and Vertisols becomes relevant. The formation of diagnostic features of Vertisols and Cryosols is due to physical processes. Despite the different mechanisms of these processes (shrinkage and swelling of clay minerals, formation and melting of ice), they lead to the development of a number of morphologically similar features at the macro-, meso-, and microlevels, including microtopography, mosaic profile patterns, wavy and discontinuous genetic horizons, cracking, types of structure, and some microfeatures. The analysis, generalization, and systematization of literature and own data on the morphology of Vertisols and Cryosols at different levels of their structural organization are discussed in this paper.
DOI: 10.1134/S1064229322100088
2023005388 Jorgenson, M. T. (Alaska Ecoscience, Fairbanks, AK); Kanevskiy, M. Z.; Jorgenson, J. C.; Liljedahl, A.; Shur, Y.; Epstein, H.; Kent, K.; Griffin, C. G.; Daanen, R.; Boldenow, M.; Orndahl, K.; Witharana, C. and Jones, B. M. Rapid transformation of tundra ecosystems from ice-wedge degradation: Global and Planetary Change, 216, Article 103921, illus. incl. 1 plate, 1 table, sketch map, 94 ref., September 2022. Includes appendices.
Ice wedges are a common form of massive ground ice that typically occupy 10-30% of the volume of upper permafrost in the Arctic and are particularly vulnerable to thawing from climate warming. In assessing the patterns and rates of ice-wedge degradation in northeastern Alaska, we found degradation was widespread and rapidly transforming the microtopography, hydrology, soils, ground ice, and vegetation of tundra ecosystems through a sequence of degradation and stabilization stages. Across an extensive mapping area (30 km2), thermokarst troughs and pits with open water (degradation-advanced) covered 0.7% overall and 1.6% in the oldest terrain in 2018. Within an area (0.5 km2) of concentrated thermokarst, undegraded and degraded ice wedges together covered 29% of the area, and all degradation stages combined increased from 2% in 1950 to 19% area in 2018. Initial degradation peaked at 9% in 2000 and initial stabilization was trending upward at 12% area in 2018, indicating slowing degradation and a transition to stabilization. Integration and reorganization of the drainage network as troughs expanded and connected reduced impounded surface water and helped slow degradation. Degradation created large changes in microtopography, trough widths, water depths, depth to wedge ice, pH, soil and ground ice characteristics, and thermal regimes among stages. Community composition completely shifted from dominance of deciduous and evergreen shrubs in tussock tundra in the undegraded stage to dominance of aquatic mosses and forbs in flooded depressions in degradation-advanced stage. Soil slumping along trough margins and rapid colonization by aquatic mosses halted the degradation, and aquatic sedges became dominant in the stabilization-initial stage. In stabilization-advanced, aquatic mosses persisted and the diversity of wet-adapted forbs, sedges, and mosses increased. Recovery back to tussock tundra, however, is unlikely. This decadal-scale transformation has major implications for arctic land cover, tundra productivity, lake expansion and drainage, soil-carbon balance, trace-gas emissions, and caribou and bird populations.
DOI: 10.1016/j.gloplacha.2022.103921
2023005932 Mena, Gabriela (University of Chile, Department of Civil Engineering, Santiago, Chile); Yoshikawa, Kenji; Schorghofer, Norbert; Pastén, César; Agustin Ochoa, Felipe; Yoshii, Yuzuru; Doi, Mamoru; Miyata, Takeshi; Takahashi, Hidenori; Casassa, Gino and Sone, Toshio. Freeze-thaw cycles and snow impact at arid permafrost region in Chajnantor Volcano, Atacama, northern Chile: Arctic, Antarctic, and Alpine Research, 53, p. 60-66, illus., 17 ref., 2021.
Permafrost occurs in the high Atacama Desert, and its thermal state was characterized at a study site 5,075 m a.s.l., at the lower regional altitude boundary for permafrost. The permafrost body is about 5 m thick and located in the hydrothermal alteration zone. The freeze–thaw layer and upper part of the permafrost layer temperatures were measured at 0 to 39 cm depth at 1-cm resolution throughout the year. The upper 3 cm of the ground experienced more than 100 freeze–thaw cycles in 2019. The maximum thaw depth was 14 cm. No significant thermal offset is observed between the annual mean of the surface temperature and the top permafrost boundary. The 14-m borehole reveals that the geothermal gradient was quite high at 200°C/km. In 2019 the seventy days of snow cover impacted the surface energy budget. Winter and summer snow conditions contribute to cooling the surface temperature regime in different ways.
DOI: 10.1080/15230430.2021.1878739
2023005936 Sun Huan (Northwest University, Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Xi'an, China); Wang Ninglian and Hou Shanshan. Twentieth century warming reflected by the Malan Glacier borehole temperatures, northern Tibetan Plateau: Arctic, Antarctic, and Alpine Research, 53, p. 227-236, illus., 35 ref., 2021.
The Tibetan Plateau is a high-elevation area in Asia and contains the largest volumes of glaciers outside the polar regions. Reconstruction of the glacier surface temperature history in this area is crucial for better understanding of the process of climate change in the Tibetan Plateau. The Tikhonov regularization method has been used on borehole temperatures measured at Malan Glacier, located on the north Tibetan Plateau, to reconstruct the surface temperature history in the twentieth century. We found that the glacier surface temperature, which rose significantly after the 1960s, increased about 1.1°C over the last century. The warmest period occurred in the 1980s to the 1990s and the highest temperature variation could be 1.5°C to 1.6°C. The results were also compared with those of nearby instrumental temperatures by Wudaoliang meteorological station and the stable oxygen isotope from the Malan ice core.
DOI: 10.1080/15230430.2021.1974667
2023005931 Swanson, David K. (U. S. National Park Service, Fairbanks, AK); Sousanes, Pamela J. and Hill, Ken. Increased mean annual temperatures in 2014-2019 indicate permafrost thaw in Alaskan national parks: Arctic, Antarctic, and Alpine Research, 53, p. 1-19, illus. incl. 2 tables, sketch maps, 88 ref., 2021.
Rising temperatures in the Arctic can result in thaw of permafrost, with widespread implications for ecosystems and infrastructure. We analyzed mean annual air and ground temperatures in the eight northernmost national parks in Alaska using data from thirty-three National Park Service climate monitoring stations and eight National Weather Service stations. Mean annual air temperatures (MAATs) from 2014 to 2019 increased in a stepwise fashion relative to the preceding thirty-year period by at least 1°C at all locations in the study area; the increase was near 2°C in Denali National Park and most of the Arctic Alaska parks and 3°C in the far western coastal areas of the Arctic parks. The increase in mean annual ground temperatures (MAGT) was approximately equal to the increase in MAAT in windswept tundra areas with minimal snow, whereas under deeper taiga and alpine snowpacks the increase in MAGT was about half as large as the increase in MAAT. If the warm temperatures observed during 2014 to 2019 persist, there will be widespread degradation of permafrost in portions of these national parks and in similar environments across Alaska.
DOI: 10.1080/15230430.2020.1859435
2023005934 Yoshikawa, Kenji (University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Hardy, Douglas R.; Narita, Kenji; Bolton, William R.; Stanilovskaya, Julia and Sparrow, Elena B. Ground thermal regimes and implications for permafrost distribution on Kilimanjaro, Tanzania: Arctic, Antarctic, and Alpine Research, 53, p. 127-145, illus. incl. 2 tables, sketch map, 37 ref., 2021.
Tropical mountain permafrost has a unique thermal regime due to ground surface exposure to strong solar radiation. The intensity of the surface offset resulting from snow cover also strongly affects the absence or presence of permafrost. Latent heat transfer and reflected solar radiation (higher albedo) that occur during the snow-covered season contribute to a positive feedback that cools the ground. Eleven ground temperature monitoring sites were established on the mountain at 2,780 to 5,820 m.a.s.l. The geothermal heat flow is locally high in the caldera of this volcano, as shown by borehole temperature data. Permafrost is located near the only glacier entirely within the caldera (Furtwängler). These three-year continuous records of ground temperature data encompass years of high and low snow cover. Our results show that the current lower boundary of permafrost is slightly above summit altitude and relict permafrost is present due to the influence of saturated sand on latent heat transfer. Permafrost tends to be lost more rapidly during drought years. The remaining permafrost seems likely to disappear in the future. The presence of permafrost and its thermal resistance depends on the ice content of caldera sand and the duration of snow cover.
DOI: 10.1080/15230430.2021.1903375
2023000354 Shmakova, L. A. (Russian Academy of Sciences, Institute of Physicochemical and Biological Problems in Soil Science, Pushchino, Russian Federation); Malavin, S. A.; Spirina, E. V.; Tutukina, M. N. and Rivkina, E. M. Microeukaryotes in the metagenomes of late Pleistocene permafrost deposits: Paleontological Journal, 54(8), p. 913-921, illus. incl. 3 tables, sketch map, 46 ref., December 2020.
The analysis of metagenomes from four Late Pleistocene permafrost samples allowed us to recognize nearly four hundred genera of protists and fungi, as well as nematodes, in the microeukaryotic assemblage. The sample of the ancient oxbow lake sediments is characterized by the highest taxonomic diversity. Heterotrophic protists and autotrophs dominated the deposits that formed under hydromorphic conditions. Fungi, in turn, prevailed in the Ice Complex deposits. In general, metagenomic analysis characterizes the assemblages from permafrost deposits more entirely than the standard methods of enrichment cultivation.
DOI: 10.1134/S003103012008016X
2023005060 Oldenborger, Greg A. (Natural Resources, Geological Survey of Canada, Ottawa, ON, Canada); Short, Naomi and LeBlanc, Anne-Marie. Electrical conductivity and ground displacement in permafrost terrain: Journal of Applied Geophysics, 181, Article 104148, illus. incl. sects., geol. sketch maps, 53 ref., October 2020.
Permafrost and ground ice are important features of the landscape that can significantly affect infrastructure in cold regions. Information on thaw susceptibility is important for predicting the behaviour of permafrost as an engineering substrate. We compare apparent conductivity surveys to ground displacement obtained from differential interferometric synthetic aperture radar with the objective of establishing apparent conductivity as an indicator of thaw susceptibility for regional characterization of terrain stability and permafrost conditions along the western coast of Hudson Bay, Nunavut. For field conditions where ground displacement and conductivity are influenced by surficial geology, there is a correlation between high seasonal and inter-annual subsidence and low apparent conductivity, and between high seasonal and inter-annual subsidence and high seasonal conductivity ratio, inferred to be indicative of high ice content and thaw-related displacement. For field conditions with no strong influence of surficial geology, a clear correspondence between subsidence and apparent conductivity does not exist. Nevertheless, the geophysical data are useful in identifying relevant factors for characterization of terrain stability such as saline permafrost and an ice-rich top of permafrost that experience significant seasonal fluctuations in unfrozen water content. When utilizing low-induction number electromagnetic surveys in permafrost terrain, apparent conductivity must be corrected for a depth-dependent temperature profile. For this study, correction factors of 6-13% are required to compensate for temperature variation, or 2.1% per °C at half-depth, but this is not necessarily applicable to other temperature profiles.
DOI: 10.1016/j.jappgeo.2020.104148
2023001215 Meyer, Michael C. (University of Innsbruck, Institute for Geology, Innsbruck, Austria); Gliganic, L. A.; May, J. H.; Merchel, S.; Rugel, G.; Schlütz, F.; Aldenderfer, M. S. and Krainer, K. Landscape dynamics and human-environment interactions in the northern foothills of Cho Oyu and Mount Everest (southern Tibet) during the late Pleistocene and Holocene: Quaternary Science Reviews, 229, Article 106127, illus. incl. sketch maps, 5 tables, sect., 152 ref., February 1, 2020.
Here we present an integrated earth surface process and paleoenvironmental study from the Tingri graben and the archaeological site of Su-re, located on the southern rim of the Tibetan plateau, spanning the past ca. 30 ka. The study area is characterized by cold climate earth surface processes and aridity due to its altitude and location in the rain shadow of the Mount Everest-Cho Oyu massif and is thus sensitive to climatic and anthropogenic perturbations. In this highly dynamic geomorphic environment, paired-cosmogenic nuclide results from boulders on a massive hummocky moraine in the southern Tingri graben reveal complex exposure histories that limit our capability of directly dating the corresponding glacial advance, and shed a note of caution on previously published single-nuclide-based exposure ages along the northern Himalaya. Based on geomorphic considerations, however, the moraine clearly represents the local last glacial maximum, and likely coincided with a ~344±109 m depression of discontinuous permafrost zone relative to today during the global last glacial maximum (gLGM). This greatly intensified permafrost and periglacial hillslope processes and led to fluvial aggradation of the valley floors of >&eq;12 m. We observe formation of a thick (>&eq;50 cm) pedo-complex starting at ca. 6.7 ka before present (BP) and erosional truncation at ca. 3.9 ka BP. Widespread landscape instability and erosion characterize the region subsequent to 3.9 ka and intensifies in the 15th century AD. Several lines of (geo)archaeological evidence, including the presence of pottery sherds, sling-shot projectiles and hammer stones within the sedimentary record, indicate human presence at Su-re since ca. 3.9 ka BP. Our data suggest that in the Su-re-Tingri area climatic conditions were warm and moist enough to allow vegetation expansion and soil formation only from ca. 6.7-3.9 ka, followed by weakening of the Indian summer monsoon (ISM) strength between ca. 4.2 and 3.9 ka, which is a prominent climatic event in the wider Asian monsoon region, and reflected in the investigation area by the 3.9 ka erosional boundary. Merging our Holocene landscape reconstruction with the geoarchaeological evidence, we speculate that the combined effect of Little Ice Age (LIA) cooling and an anthropogenic overuse of the landscape led to climatically induced landscape degradation and ultimately to an anthropogenically triggered ecological collapse in the 15th century. Such a scenario is in-line with regional historical data on declining monastery construction and migration of the ethnic group of the Sherpas. From an earth surface dynamics perspective, we find that transient landscape processes on the southern rim of the Tibetan plateau are strongly linked to millennial scale changes in the ISM intensity and duration. We identify three types of unidirectional non-linear ISM-landscape interactions. Given that the Tibetan plateau is the largest high-altitude landmass on our planet and our limited understanding of several of the key earth surface processes on the plateau, we pinpoint the need for more long-term (Quaternary scale) empirical data particularly on permafrost and periglacial processes and human-environment interactions.
DOI: 10.1016/j.quascirev.2019.106127
2023001218 Zhang Dongliang (Chinese Academy of Sciences, Xinjiang Institute of Ecology and Geography, State Key Laboratory of Desert and Oasis Ecology, Urumqi, China); Chen Xi; Li Yaoming; Wang Wei; Sun Aizhi; Yang Yunpeng; Ran Min and Feng Zhaodong. Response of vegetation to Holocene evolution of westerlies in the Asian central arid zone: Quaternary Science Reviews, 229, Article 106138, illus. incl. 3 tables, sketch map, 97 ref., February 1, 2020.
Based on 50 pollen sequences inferred from the westerlies-influenced Asian Central Arid Zone, we reconstructed the Holocene vegetation dynamics of four forest types indicated by Picea, Betula, Pinus sibirica and Pinus sylvestris as well as steppe type by Artemisia and desert type by Chenopodiaceae. The sensitivities of these vegetation types to Holocene temperature and precipitation changes were analyzed according to four grouping: temperature, precipitation, latitude and elevation of sites. The results revealed that there was a clear delay of forest expansions in the early Holocene along the S-N gradient, most likely influenced by the existed permafrost extent in the Northern Hemisphere. The increasing precipitation driven by the westerlies in the early Holocene would have first reached the threshold for forest expansion in high-elevation sub-region, but was significantly delay for low-elevation sub-region. Steppe expanded in low-elevation and highland sub-regions in the cooling and wetting late-Holocene. Holocene vegetation dynamics differed across vegetation types with Pinus sibirica and Pinus sylvestris that were very sensitive to westerlies-associated precipitation changes, while Picea and Artemisia were more sensitive to temperature changes. A decreasing sensitivity of forests was found with different types following an evident increase in precipitation and an increasing sensitivity for steppe was observed following a gradual reduction of temperature in the late Holocene. Our research offers new insights into the mechanisms of individualistic responses of plant types and the different responses of vegetation to the Holocene westerlies evolution in the Asian Central Arid Zone and improves our ability to predict the vegetation dynamics (particularly forest) in the Asian Central Arid Zone under global warming conditions.
DOI: 10.1016/j.quascirev.2019.106138
2023005917 Fujii, Kazumichi (Forestry and Forest Products Research Institute, Division of Forest Soils, Tsukuba, Japan); Yasue, Koh; Matsuura, Yojiro and Osawa, Akira. Soil conditions required for reaction wood formation of drunken trees in a continuous permafrost region: Arctic, Antarctic, and Alpine Research, 52, p. 47-59, illus. incl. 2 tables, sketch map, 27 ref., 2020.
Black spruce trees lean to form "drunken" forest on degrading permafrost; however, the causes of tree leaning on continuous permafrost remain unclear. Leaning events are recorded by reaction wood formation in tree rings, and it remains unclear what soil conditions are required for reaction wood formation of drunken trees. Tree disk morphology and soil hummock properties were examined for fifty tree-mound combinations in Northwest Territories, Canada. Spruce trees growing on mound edges form reaction wood on the downslope sides of their trunks. Reaction wood formation in mature trees was greatest in stem tissues between ground level and 30 cm aboveground. Reaction wood formation occurred only in trees growing on mound edges. The extent of reaction wood formation was higher in trees growing in clayey soils than in trees on sandy soils. For trees growing on clayey mound edges, the extent of reaction wood formation decreased with increasing permafrost table depth. Black spruce tree rings formed between ground level and 30 cm aboveground could record movement of clayey soil hummocks over shallow, underlying permafrost tables. A combination of clayey soil texture and shallow permafrost table is likely required for development of hummocks and drunken forests on the continuous permafrost region studied.
DOI: 10.1080/15230430.2020.1712858
2023005927 Liu Jia (China Geological Survey, Key Laboratory of Unconventional Oil and Gas Geology, Beijing, China); Jiang Guanli; Wu Qingbai; Zhang Tingjun and Gao Siru. Regional climate change signals inferred from a borehole temperature profile in Muri, Qilian Mountain, using the Tikhonov method: Arctic, Antarctic, and Alpine Research, 52, p. 450-460, illus. incl. 4 tables, sketch map, 52 ref., 2020.
Within the gas hydrate drilling project in the Qilian Mountain permafrost region, a temperature-depth profile measured from borehole DK-12 in Juhugeng of Muri Coalfield, Tianjun County, Qinghai Province, China, was analyzed to infer recent climate changes. The long-term surface temperature and thermal gradient were retrieved from borehole temperature measurements. The ground surface temperature (GST) changes were reconstructed by inversion of transient temperature perturbations through solving an inverse heat conduction problem using the Tikhonov method. Based on the instability of this kind of inverse problem and the nature of method-dependent features of borehole paleothermometry, we initially applied the Tikhonov regularization technique to obtain a stable past GST variation pattern with relatively low resolution. The inversion results showed that this region experienced temperature fluctuation with a total warming of 3°C (±1.6°C) from 1400 to the 2010s and a more exacerbated warming starting from the 1960s. The GST trend fit the surface air temperature observation trend from the nearest Yeniugou meteorological station. This work fills the gap created by limited meteorological records in the Muli area and extends knowledge of ground surface temperature trends going back more than ten centuries.
DOI: 10.1080/15230430.2020.1801149
2023005915 Luo Xian (Yunnan University, Institute of International Rivers and Eco-security, Kunming, China); Fan Xuemei; Ji Xuan and Li Yungang. Hydrological impacts of interannual variations in surface soil freezing processes in the upper Nu-Salween River basin: Arctic, Antarctic, and Alpine Research, 52, p. 1-12, illus. incl. 1 table, sketch map, 42 ref., 2020.
The upper Nu-Salween River basin in the Tibetan Plateau is mainly covered with seasonal frozen soils. We used daily surface freeze-thaw states, detected from Special Sensor Microwave/Imager (SSM/I) daily brightness temperature data, to analyze the variations in surface freeze-thaw states and the relationship with air temperature. We also examined baseflow to explore the influences of interannual variations in the start time of soil freezing on hydrological processes. The results showed that (1) interannual air temperature fluctuations led to differences in the area and start time of surface freezing. When surface soil froze, flow was mainly dependent on existing groundwater storage. (2) The interannual variation in the surface freezing time directly affected the flow generation processes. When soil water froze and remained in the frozen layer, it was hard to generate surface flow, so flow mainly consisted of baseflow, causing the proportion of the baseflow in the total flow to gradually increase. (3) The surface freeze-thaw states obtained from the passive microwave remote sensing data may be applied to support further research on the hydrological impacts of freeze-thaw cycle variations in plateau mountain basins.
DOI: 10.1080/15230430.2019.1698893
2023005916 Munkhjargal, Munkhdavaa (Heidelberg University, Institute of Geography, Heidelberg, Germany); Yadamsuren, Gansukh; Yamkhin, Jambaljav and Menzel, Lucas. Ground surface temperature variability and permafrost distribution over mountainous terrain in northern Mongolia: Arctic, Antarctic, and Alpine Research, 52, p. 13-26, illus. incl. 5 tables, sketch map, 46 ref., 2020.
Permafrost plays an important role in numerous environmental processes at high latitudes and in high mountain areas. The identification of mountain permafrost, particularly in the discontinuous permafrost regions, is challenging due to limited data availability and the high spatial variability of controlling factors. This study focuses on mountain permafrost in a data-scarce environment of northern Mongolia, at the interface between the boreal forest and the dry steppe mid-latitudes. In this region, the ground temperature has been increasing continuously since 2011 and has a high spatial variability due to the distribution of incoming solar radiation, as well as seasonal snow and vegetation cover. We analyzed the effect of these controlling factors to understand the climate-permafrost relationship based on in situ observations. Furthermore, mean ground surface temperature (MGST) was calculated at 30-m resolution to predict permafrost distribution. The calculated MGST, with a root mean square error of ±1.4°C, shows permafrost occurrence on north-facing slopes and at higher elevations and absence on south-facing slopes. Borehole temperature data indicate a serious wildfire-induced permafrost degradation in the region; therefore, special attention should be paid to further investigations on ecosystem resilience and climate change mitigation in this region.
DOI: 10.1080/15230430.2019.1704347
2023005921 Wauthy, Maxime (Université du Québec à Chicoutimi, Département des sciences fondamentales, Saguenay, QC, Canada) and Rautio, Milla. Emergence of steeply stratified permafrost thaw ponds changes zooplankton ecology in subarctic freshwaters: Arctic, Antarctic, and Alpine Research, 52, p. 177-190, illus. incl. 3 tables, 74 ref., 2020.
Climate change and associated permafrost thaw are creating new shallow waterbodies in vast regions of the circumpolar Arctic. These thaw ponds are characterized by high concentrations of colored dissolved organic matter originating from the degrading watershed, inducing a strong vertical thermal and oxygen (O2) stratification. We investigated the zooplankton community and biomass in eight subarctic thaw ponds and evaluated how zooplankton respond to this stratification. In a subset of three ponds, we further examined how other environmental variables, including essential fatty acids (EFA) concentration and phytoplankton, bacteria, and larval phantom midge Chaoborus biomass stratify and contribute to the vertical distribution of zooplankton in this increasingly common type of arctic freshwater system. The zooplankton community was extremely abundant in all ponds (up to 3,548 ind L-1) and dominated mainly by rotifers (35-93 percent of the biomass). Most zooplankton aggregated at the interface between the shallow well-oxygenated mixed surface layer and the deeper hypoxic but algal-rich stratified layer, and their distribution was affected by a combination of O2, Chaoborus, phytoplankton, and EFA that were supplied from opposite directions. Our findings show how water column stratification deeply affects the ecology of planktonic organisms in circumpolar freshwaters and indicate Arctic zooplankton species composition is expected to deeply change with the ongoing warming and browning.
DOI: 10.1080/15230430.2020.1753412
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The USPA is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute (AGI), with support from the National Science Foundation (NSF), has migrated the previous Cold Regions Bibliography to a new platform. Included are the USPA supported PMAs dating back to 2011. The Bibliography is searchable at 
