March 2021 Monthly Permafrost Alert (PMA) Program

The U.S. Permafrost Association is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute, with support from the National Science Foundation, has "migrated" the previous Cold Regions Bibliography to a new platform. Included are the US Permafrost Association supported Monthly Permafrost Alerts dating back to 2011. The Bibliography is searchable at :

Entries in each category are listed in chronological order starting with the most recent citation.

The individual Monthly Permafrost Alerts are found on the US Permafrost Association website :

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2021024446 Blondeau, Sylvain (Université Lumière Lyon, Department of Geography, Bron, France); Gunnell, Y. and Jarman, D. Rock slope failure in the Western Alps; a first comprehensive inventory and spatial analysis: Geomorphology, 380, Article no. 107622, illus. incl. 4 tables, sketch map, May 1, 2021. Based on Publisher-supplied data.

Rock slope failure (RSF) occurs in different contexts but is typically reported either as (i) single-category inventories or (ii) single-site geotechnical monographs. Few studies have sought to evaluate the spatial incidence of all modes of RSF conjointly, and to infer scenarios of regional landscape evolution from observed patterns of cumulative rock slope overstressing. Here we present the results of a systematic inventory of rock avalanches, rockfalls, rockslides, and gravitational rock slope deformations in the Western Alps (France, Italy, Switzerland) conducted using satellite imagery made available in Google Earth as a detection tool, and aided by preliminary ground-truth checks. The inventory totals 1416 montane RSFs, impacting 9.1% of the study area. Underpinned by GIS tools, the study further examines the spatial distribution of RSF with consideration for (i) predisposing factors (typically: lithology, geological structure), and (ii) preparatory factors (geomorphological process regimes that drives a given slope segment to the point of failure). The latter encompass slower variables (e.g., long-term crustal stress regime, cumulative residence time above equilibrium line altitudes) and faster variables (e.g., short-span glacier-related stresses, permafrost thaw, seismicity). RSF density patterns helped to define seven RSF super-hotspots (large diversity of RSF modes, up to 50% of displaced rock masses/unit area), which define the most intensely overstressed areas of the Western Alps. These super-hotspots occur at sites where highly dynamic, thick, warm-based glaciers above the equilibrium line either intersected (middle Maurienne) or followed the strike of (middle Isère) N-S bands of highly susceptible lithologies and structures during the Quaternary. The widespread incidence of rock slope deformation (cumulative area: 1760 km2, i.e., nearly 3 times the total of the other three RSF categories combined) appears further correlated with the low tectonic activity of the orogen and with its areas dominated by an extensional tectonic regime west of the Penninic Frontal Thrust. This contrasts with seismically active orogens, e.g., New Zealand's Southern Alps, where rock slope deformation is scarce compared to rock avalanches and shallow landslides.

DOI: 10.1016/j.geomorph.2021.107622

2021025991 Liu Lei (Chinese Academy of Sciences, Institute of Geographical Sciences and Natural Resources Research, Beijing, China); Zhao Dongsheng; Wei Junqi; Zhuang, Qianlai; Gao Xuan; Zhu Yu; Zhang Jiacheng; Guo Caiyun and Zheng Du. Permafrost sensitivity to global warming of 1.5°C and 2°C in the Northern Hemisphere: Environmental Research Letters, 16(3), Paper no. 034038, illus. incl. 1 table, 30 ref., March 2021.

Permafrost degradation induced by climate warming is widely observed in the Northern Hemisphere. However, changes in permafrost sensitivity to climate warming (PSCW) in the future remains unclear. This study examined the changes in permafrost distribution in the Northern Hemisphere under global warming of 1.5°C and 2°C, and then characterized the spatial and temporal characteristics of PSCW. Global warming of 1.5°C and 2°C would result in 17.8±5.3% and 28.3±7.2% degradation of permafrost area under the climate scenario of Representative Concentration Pathway (RCP) 4.5, respectively, and 18.7±4.6% and 28.1±7.2% under the RCP 8.5, respectively. Permafrost tends to be more sensitive to climate change under the RCP 8.5 than RCP 4.5. PSCW shows small temporal variations in the 21st century under both RCPs, indicating a relatively stable sensitivity to warming on a hemisphere scale. However, PSCW varies greatly among regions, with high values at low latitudes and low values towards high latitudes. Air temperature is a major cause for the spatial heterogeneity of PSCW, explaining 66% of its variations. Permafrost under a warmer climate scenario tends to be more sensitive to the warming. Reducing snow depth and rising air temperature collectively enhances the permafrost sensitivity. Increasing in soil water content, by contrast, reduces the effect of warming. Permafrost in the south of the Northern Hemisphere is most vulnerable to climate warming. Our study highlights that permafrost in the region will respond differently under different warming scenarios across space (e.g. north vs south) and time (e.g. summer vs winter) in this century. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/abd6a8

2021025986 Sim, Thomas G. (University of Leeds, School of Geography, Leeds, United Kingdom); Swindles, Graeme T.; Morris, Paul J.; Baird, Andy J.; Cooper, Claire L.; Gallego-Sala, Angela V.; Charman, Dan J.; Roland, Thomas P.; Borken, Werner; Mullan, Donal J.; Aquino-López, Marco A. and Galka, Mariusz. Divergent responses of permafrost peatlands to recent climate change: Environmental Research Letters, 16(3), Paper no. 034001, illus. incl. sketch maps, 66 ref., March 2021.

Permafrost peatlands are found in high-latitude regions and store globally-important amounts of soil organic carbon. These regions are warming at over twice the global average rate, causing permafrost thaw, and exposing previously inert carbon to decomposition and emission to the atmosphere as greenhouse gases. However, it is unclear how peatland hydrological behaviour, vegetation structure and carbon balance, and the linkages between them, will respond to permafrost thaw in a warming climate. Here we show that permafrost peatlands follow divergent ecohydrological trajectories in response to recent climate change within the same rapidly warming region (northern Sweden). Whether a site becomes wetter or drier depends on local factors and the autogenic response of individual peatlands. We find that bryophyte-dominated vegetation demonstrates resistance, and in some cases resilience, to climatic and hydrological shifts. Drying at four sites is clearly associated with reduced carbon sequestration, while no clear relationship at wetting sites is observed. We highlight the complex dynamics of permafrost peatlands and warn against an overly-simple approach when considering their ecohydrological trajectories and role as C sinks under a warming climate. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/abe00b

2021025990 Walter Anthony, K. M. (University of Alaska, Water and Environmental Research Center, Fairbanks, AK); Lindgren, P.; Hanke, P.; Engram, M.; Anthony, P.; Daanen, R. P.; Bondurant, A.; Liljedahl, A. K.; Lenz, J.; Grosse, G.; Jones, B. M.; Brosius, L.; James, S. R.; Minsley, B. J.; Pastick, N. J.; Munk, J.; Chanton, J. P.; Miller, C. E. and Meyer, F. J. Decadal-scale hotspot methane ebullition within lakes following abrupt permafrost thaw: Environmental Research Letters, 16(3), Paper no. 035010, illus. incl. 4 tables, 40 ref., March 2021.

Thermokarst lakes accelerate deep permafrost thaw and the mobilization of previously frozen soil organic carbon. This leads to microbial decomposition and large releases of carbon dioxide (CO2) and methane (CH4) that enhance climate warming. However, the time scale of permafrost-carbon emissions following thaw is not well known but is important for understanding how abrupt permafrost thaw impacts climate feedback. We combined field measurements and radiocarbon dating of CH4 ebullition with (a) an assessment of lake area changes delineated from high-resolution (1-2.5 m) optical imagery and (b) geophysical measurements of thaw bulbs (taliks) to determine the spatiotemporal dynamics of hotspot-seep CH4 ebullition in interior Alaska thermokarst lakes. Hotspot seeps are characterized as point-sources of high ebullition that release 14C-depleted CH4 from deep (up to tens of meters) within lake thaw bulbs year-round. Thermokarst lakes, initiated by a variety of factors, doubled in number and increased 37.5% in area from 1949 to 2009 as climate warmed. Approximately 80% of contemporary CH4 hotspot seeps were associated with this recent thermokarst activity, occurring where 60 years of abrupt thaw took place as a result of new and expanded lake areas. Hotspot occurrence diminished with distance from thermokarst lake margins. We attribute older 14C ages of CH4 released from hotspot seeps in older, expanding thermokarst lakes (14CCH4 20079±1227 years BP, mean±standard error (s.e.m.) years) to deeper taliks (thaw bulbs) compared to younger 14CCH4 in new lakes (14CCH4 8526±741 years BP) with shallower taliks. We find that smaller, non-hotspot ebullition seeps have younger 14C ages (expanding lakes 7473±1762 years; new lakes 4742±803 years) and that their emissions span a larger historic range. These observations provide a first-order constraint on the magnitude and decadal-scale duration of CH4-hotspot seep emissions following formation of thermokarst lakes as climate warms. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/abc848

2021025992 Wang Ping (Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources Research, Beijing, China); Huang Qiwei; Pozdniakov, Sergey P.; Liu Shiqi; Ma Ning; Wang Tianye; Zhang Yongqiang; Yu Jingjie; Xie Jiaxin; Fu, Guobin; Frolova, Natalia L. and Liu Changming. Potential role of permafrost thaw on increasing Siberian river discharge: Environmental Research Letters, 16(3), Paper no. 034046, illus., 29 ref., March 2021.

Despite the increasing Siberian river discharge, the sensitivity of streamflow to climate forcing/permafrost thawing is poorly quantified. Based on the Budyko framework and superposition principles, we detected and attributed the changes in streamflow regimes for the three great Siberian rivers (Ob, Yenisei, and Lena) during 1936-2019. Over the past 84 years, streamflow of Ob, Yenisei and Lena has increased by ~7.7%, 7.4% and 22.0%, respectively. Intensified precipitation induced by a warming climate is a major contributor to increased annual streamflow. However, winter streamflow appears to be particularly sensitive to temperature. Whilst rising temperature can reduce streamflow via evapotranspiration, it can enhance groundwater discharge to rivers due to permafrost thawing. Currently, every 1°C rise in temperature likely leads to 6.1%-10.5% increase in groundwater discharge, depending on the permafrost condition. For permafrost-developed basins, the contribution to increased streamflow from thawing permafrost will continue to increase in the context of global warming. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/abe326

2021026063 Hiyama, Tetsuya (Nagoya University, Institute for Space-Earth Environmental Research, Nagoya, Japan); Dashtseren, Avirmed; Asai, Kazuyoshi; Kanamori, Hironari; Iijima, Yoshihiro and Ishikawa, Mamoru. Groundwater age of spring discharges under changing permafrost conditions; the Khangai Mountains in central Mongolia: Environmental Research Letters, 16(1), Paper no. 015008, illus. incl. sketch map, 33 ref., January 2021.

Obtaining a better understanding of groundwater dynamics in permafrost zones is a critical issue in permafrost hydrology. This includes assessing the impacts of climate change on permafrost thaw and ground ice-melt. Both permafrost thaw and ground ice-melt can be related to groundwater discharges (i.e. spring discharges), and spring water is an important local water resource; accordingly, changes in these processes can have large impacts on local people and their subsistence activities. To detect permafrost thaw and ground ice-melt in the permafrost zone of Mongolia, groundwater ages of several spring discharges were determined using two transient tracers: tritium (3H) and chlorofluorocarbons (CFCs). Spring water samples were collected seasonally from 2015 to 2019 at seven spring sites around the Khangai Mountains in central Mongolia. The sites included two thermokarst landscapes on the northern and southern sides of the mountains. The 3H and CFC concentrations in the spring water in the thermokarst landscapes were very low, especially on the southern side of the mountains, and the estimated mean groundwater age for these sites was older than that for the other sampled springs. Consequently, the young water ratios of the thermokarst sites were lower than those for the other springs. This ratio, however, showed a gradual increase with time, which indicates that recently recharged rainwater began to contribute to the spring discharge at the thermokarst sites. An atmospheric water budget analysis indicated that net recharge from modern and recent precipitation to shallow groundwater in the summer season was almost zero on the southern side of the mountains. Thus, we inferred that the spring water at the thermokarst sites on the southern side of the mountains contained large amounts of ground ice-melt water. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/abd1a1

2021025767 Buckel, Johannes (Technische Universiät Braunschweig, Institute for Geophysics and Extraterrestrial Physics, Braunschweig, Germany); Reinosch, Eike; Hördt, Andreas; Zhang Fan; Riedel, Björn; Gerke, Markus; Schwalb, Antje and Mäusbacher, Roland. Insights into a remote cryosphere; a multi-method approach to assess permafrost occurrence at the Qugaqie Basin, western Nyainqentanglha Range, Tibetan Plateau: The Cryosphere (Online), 15(1), p. 149-168, illus. incl. sketch map, 127 ref., 2021.

Permafrost as a climate-sensitive parameter and its occurrence and distribution play an important role in the observation of global warming. However, field-based permafrost distribution data and information on the subsurface ice content in the large area of the southern mountainous Tibetan Plateau (TP) are very sparse. Existing models based on boreholes and remote sensing approaches suggest permafrost probabilities for most of the Tibetan mountain ranges. Field data to validate permafrost models are generally lacking because access to the mountain regions in extreme altitudes is limited. The study provides geomorphological and geophysical field data from a north-orientated high-altitude catchment in the western Nyainqentanglha Range. A multi-method approach combines (A) geomorphological mapping, (B) electrical resistivity tomography (ERT) to identify subsurface ice occurrence and (C) interferometric synthetic aperture radar (InSAR) analysis to derive multi-annual creeping rates. The combination of the resulting data allows an assessment of the lower occurrence of permafrost in a range of 5350 and 5500 m above sea level (a.s.l.) in the Qugaqie basin. Periglacial landforms such as rock glaciers and protalus ramparts are located in the periglacial zone from 5300-5600 m a.s.l. The altitudinal periglacial landform distribution is supported by ERT data detecting ice-rich permafrost in a rock glacier at 5500 m a.s.l. and ice lenses around the rock glacier (5450 m a.s.l.). The highest multiannual creeping rates up to 150 mm yr-1 are typically observed on these rock glaciers. This study closes the gap of unknown state of periglacial features and potential permafrost occurrence in a high-elevated basin in the western Nyainqentanglha Range (Tibetan Plateau).

DOI: 10.5194/tc-15-149-2021

2021025774 McKenzie, Jeffrey M. (McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada); Kurylyk, Barret L.; Walvoord, Michelle A.; Bense, Victor F.; Fortier, Daniel; Spence, Christopher and Grenier, Christophe. Invited perspective; what lies beneath a changing Arctic?: The Cryosphere (Online), 15(1), p. 479-484, illus., 45 ref., 2021.

As permafrost thaws in the Arctic, new subsurface pathways open for the transport of groundwater, energy, and solutes. We identify different ways that these subsurface changes are driving observed surface consequences, including the potential for increased contaminant transport, modification to water resources, and enhanced rates of infrastructure (e.g. buildings and roads) damage. Further, as permafrost thaws it allows groundwater to transport carbon, nutrients, and other dissolved constituents from terrestrial to aquatic environments via progressively deeper subsurface flow paths. Cryohydrogeology, the study of groundwater in cold regions, should be included in northern research initiatives to account for this hidden catalyst of environmental and societal change.

DOI: 10.5194/tc-15-479-2021

2021025771 Romeyn, Rowan (University of Tromso, Department of Geosciences, Tromso, Norway); Hanssen, Alfred; Ruud, Bent Ole; Stemland, Helene Meling and Johansen, Tor Arne. Passive seismic recording of cryoseisms in Adventdalen, Svalbard: The Cryosphere (Online), 15(1), p. 283-302, illus. incl. sketch map, 42 ref., 2021.

A series of transient seismic events were discovered in passive seismic recordings from 2-D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images using an apparent offset re-sorting and inter-trace delay minimisation technique to locate the seismic source, followed by cross-correlation beamforming dispersion imaging. The dispersion images are highly analogous to surface wave studies of pavements and display a complex multimodal dispersion pattern. Supported by theoretical modelling based on a highly simplified arrangement of horizontal layers, we infer that a ~3.5-4.5 m thick, stiff, high-velocity layer overlies a ~30 m thick layer that is significantly softer and slower at our study site. Based on previous studies we link the upper layer with syngenetic ground ice formed in aeolian sediments, while the underlying layer is linked to epigenetic permafrost in marine-deltaic sediments containing unfrozen saline pore water. Comparing events from spring and autumn indicates that temporal variation can be resolved via passive seismic monitoring. The transient seismic events that we record occur during periods of rapidly changing air temperature. This correlation, along with the spatial clustering along the elevated river terrace in a known frost polygon, ice-wedge area and the high proportion of surface wave energy, constitutes the primary evidence for us to interpret these events as frost quakes, a class of cryoseism. In this study we have proved the concept of passive seismic monitoring of permafrost in Adventdalen, Svalbard.

DOI: 10.5194/tc-15-283-2021

2021026021 Doloisio, Natalia (Université Paris Saclay, University of Versailles Saint Quentin en Yvelines, Paris, France) and Vanderlinden, Jean-Paul. The perception of permafrost thaw in the Sakha Republic (Russia); narratives, culture and risk in the face of climate change: Polar Science, 26, Article no. 100589, illus., 32 ref., December 2020. Includes appendix.

This article focuses on the social representations of permafrost thaw among people who were born in different regions of the Sakha Republic (Russia) and live in the regional capital city of Yakutsk. Our research aims to obtain a better understanding of the new risk patterns associated to permafrost thaw through the collection and subsequent analysis of narratives of personal experiences in order to identify the main concerns, how these are defined and which coping strategies are considered by local inhabitants. Our respondents insightfully characterized the nature of the multiple interrelated processes and associations that they identified. According to locals' grasp, climate change and permafrost thaw's impacts exceed the merely physical and material dimensions, unchaining simultaneous and deep transformations in their culture. More specifically, physical degradation threatens their symbolic representations, the material practices and the emotional ties that they have developed in that specific land. They also expressed the need for potential mitigation strategies at both a regional and local scale.

DOI: 10.1016/j.polar.2020.100589

2021026195 Lu Ping (Tongji University, College of Surveying and Geo-Informatics, Shanghai, China); Han Jiangping; Li Zhenshi; Xu Ruguo; Li Rongxing; Hao Tong and Qiao Gang. Lake outburst accelerated permafrost degradation on Qinghai-Tibet Plateau: in Terra at 20 (Nigro, Joseph, editor; et al.), Remote Sensing of Environment, 249, 19 p., illus. incl. 3 tables, sketch maps, 87 ref., November 2020.

DOI: 10.1016/

2021024302 Bui, Minh (UiT The Arctic University of Norway, Department of Technology and Safety, Tromso, Norway); Lu, Jinmei and Nie, Linmei. A review of hydrological models applied in the permafrost-dominated Arctic region: Geosciences (Basel), 10(10), Article 401, illus. incl. 5 tables, 171 ref., October 2020.

The Arctic region is the most sensitive region to climate change. Hydrological models are fundamental tools for climate change impact assessment. However, due to the extreme weather conditions, specific hydrological process, and data acquisition challenges in the Arctic, it is crucial to select suitable hydrological model(s) for this region. In this paper, a comprehensive review and comparison of different models is conducted based on recently available studies. The functionality, limitations, and suitability of the potential hydrological models for the Arctic hydrological process are analyzed, including: (1) The surface hydrological models Topoflow, DMHS (deterministic modeling hydrological system), HBV (Hydrologiska Byrans Vattenbalansavdelning), SWAT (soil and water assessment tool), WaSiM (water balance simulation model), ECOMAG (ecological model for applied geophysics), and CRHM (cold regions hydrological model); and (2) the cryo-hydrogeological models ATS (arctic terrestrial simulator), CryoGrid 3, GEOtop, SUTRA-ICE (ice variant of the existing saturated/unsaturated transport model), and PFLOTRAN-ICE (ice variant of the existing massively parallel subsurface flow and reactive transport model). The review finds that Topoflow, HBV, SWAT, ECOMAG, and CRHM are suitable for studying surface hydrology rather than other processes in permafrost environments, whereas DMHS, WaSiM, and the cryo-hydrogeological models have higher capacities for subsurface hydrology, since they take into account the three phase changes of water in the near-surface soil. Of the cryo-hydrogeological models reviewed here, GEOtop, SUTRA-ICE, and PFLOTRAN-ICE are found to be suitable for small-scale catchments, whereas ATS and CryoGrid 3 are potentially suitable for large-scale catchments. Especially, ATS and GEOtop are the first tools that couple surface/subsurface permafrost thermal hydrology. If the accuracy of simulating the active layer dynamics is targeted, DMHS, ATS, GEOtop, and PFLOTRAN-ICE are potential tools compared to the other models. Further, data acquisition is a challenging task for cryo-hydrogeological models due to the complex boundary conditions when compared to the surface hydrological models HBV, SWAT, and CRHM, and the cryo-hydrogeological models are more difficult for non-expert users and more expensive to run compared to other models.

DOI: 10.3390/geosciences10100401

2021024322 Chernykh, Denis (Far Eastern Branch of the Russian Academy of Sciences, V.I. Il'ichev Pacific Oceanological Institute, Vladivostok, Russian Federation); Yusupov, Vladimir; Salomatin, Aleksandr; Kosmach, Denis; Shakhova, Natalia; Gershelis, Elena; Konstantinov, Anton; Grinko, Andrey; Chuvilin, Evgeny; Dudarev, Oleg; Koshurnikov, Andrey and Semiletov, Igor. Sonar estimation of methane bubble flux from thawing subsea permafrost; a case study from the Laptev Sea shelf: Geosciences (Basel), 10(10), Article 411, illus. incl. sects., sketch maps, 46 ref., October 2020.

Seeps found offshore in the East Siberian Arctic Shelf may mark zones of degrading subsea permafrost and related destabilization of gas hydrates. Sonar surveys provide an effective tool for mapping seabed methane fluxes and monitoring subsea Arctic permafrost seepage. The paper presents an overview of existing approaches to sonar estimation of methane bubble flux from the sea floor to the water column and a new method for quantifying CH4 ebullition. In the suggested method, the flux of methane bubbles is estimated from its response to insonification using the backscattering cross section. The method has demonstrated its efficiency in the case study of single- and multi-beam acoustic surveys of a large seep field on the Laptev Sea shelf.

DOI: 10.3390/geosciences10100411

2021024329 Chuvilin, Evgeny (Skolkovo Institute of Science and Technology (Skoltech), Center for Hydrocarbon Recovery, Moscow, Russian Federation); Ekimova, Valentina; Davletshina, Dinara; Sokolova, Natalia and Bukhanov, Boris. Evidence of gas emissions from permafrost in the Russian Arctic: Geosciences (Basel), 10(10), Article 383, illus. incl. 2 tables, 102 ref., October 2020.

The active emission of gas (mainly methane) from terrestrial and subsea permafrost in the Russian Arctic has been confirmed by ample evidence. In this paper, a generalization and some systematization of gas manifestations recorded in the Russian Arctic is carried out. The published data on most typical gas emission cases have been summarized in a table and illustrated by a map. The tabulated data include location, signatures, and possible sources of each gas show, with respective references. All events of onshore and shelf gas release are divided into natural and man-caused. and the natural ones are further classified as venting from lakes or explosive emissions in dryland conditions that produce craters on the surface. Among natural gas shows on land, special attention is paid to the emission of natural gas from Arctic lakes, as well as gas emissions with craters formation. In addition, a description of the observed man-caused gas manifestations associated with the drilling of geotechnical and production wells in the Arctic region is given. The reported evidence demonstrates the effect of permafrost degradation on gas release, especially in oil and gas fields.

DOI: 10.3390/geosciences10100383

2021024342 Gubin, S. V. (Russian Academy of Sciences, Institute of Physicochemical and Biological Problems of Soil Science, Pushchino, Russian Federation) and Lupachev, A. V. Pedogenesis in the tundra zone of coastal lowlands of northeastern Siberia: Eurasian Soil Science, 53(10), p. 1365-1373, illus. incl. sketch map, 43 ref., October 2020.

Coastal lowlands of northeastern Siberia are composed of the Pleistocene ice-rich organic-containing loamy sediments of the Ice Complex (yedoma) and products of their transformation in the Holocene. In the tundra zone, three major trends of modern pedogenesis depending on the geomorphic position and age of particular landforms have been identified. On the interfluves affected by thermokarst processes in the Holocene, somewhat elevated remains of the Late Pleistocene Ice Complex alternate with vast thermokarst depressions (alases) with lakes. Cryozems are developed in automorphic plain positions and on the upper parts of slopes. The profiles of these soils are strongly affected by cycles of frost boiling and cryoturbation; under their influence, specific suprapermafrost accumulative organomineral horizons are formed. Gleyzation predominates in the soils of the low- and middle-level Holocene terraces of alases. Peat accumulation is progressively developed in the bottoms of alas depressions.

DOI: 10.1134/S1064229320100087

2021024216 Lolaev, Alan (Russian Academy of Sciences, Vladikavkaz Scientific Centre, Vladikavkaz, Russian Federation); Oganesyan, Aleksan; Badoev, Alexander and Oganesyan, Emil. Tailing dams formation algorithm: Arabian Journal of Geosciences, 13(19), Article no. 974, 4 ref., October 2020. Based on Publisher-supplied data.

The object of research of the present work is the tailing dump, located on the territory of north of Siberia. Based on the operating conditions of alluvial storage in permafrost, it should be noted that the increase in the annual capacity of the layer may not provide its complete consolidation during short spring-summer period before freezing. Thus, it will reduce the stability of the structure. In order to optimize the inwash technology of tailing dam, it is necessary to determine the time of tail's consolidation. On the basis of laboratory tests, the approach to coefficient definition of filtrational and secondary consolidation of tails during alluvium depending on a physical condition, density, water saturation degree, and the mathematical model to calculate the time of their consolidation has been developed. The results obtained from researches can be successfully used as a basis for constructing consolidation models of required layer tails.

DOI: 10.1007/s12517-020-05990-8

2021026004 Markkula, Inkeri (University of Turku, Zoological Museum, Biodiversity Unit, Turku, Finland) and Kuhry, Peter. Subfossil oribatid mite communities indicate Holocene permafrost dynamics in Canadian mires: Boreas, 49(4), p. 730-738, illus. incl. 2 tables, sketch map, 54 ref., October 2020.

Permafrost thaw in peatlands is one of the most widespread and worrying consequences of climate warming in the sub-Arctic area. To predict future climate feedbacks, it is important to study the history of permafrost aggradation and thaw. Plant macrofossil analysis with radiocarbon dating has been widely used in detecting past permafrost dynamics in peatlands, however, due to a lack of permafrost-specific plant indicator species, determining the exact timing of permafrost aggradation remains a challenge. In this study, we investigated if oribatid mites can be used to determine Holocene permafrost aggradation and degradation in Canadian mires. Based on analyses of subfossil oribatid mite assemblages of Holocene peat profiles from two mires in the Hudson Bay Lowlands area, our results suggest that two species, Carabodes labyrinthicus and Neoribates aurantiacus, are useful bioindicators, which can be used in palaeoecological studies determining permafrost histories. Moreover, our results show that subfossil oribatid mite remains can reveal periods of permafrost, which cannot be determined with certainty based on plant macrofossils alone. Abstract Copyright (2021), John Wiley & Sons, Ltd.

DOI: 10.1111/bor.12444

2021024314 Oblogov, Gleb E. (Russian Academy of Sciences, Siberian Branch, Institute of the Earth's Cryosphere, Tyumen, Russian Federation); Vasiliev, Alexander A.; Streletskaya, Irina D.; Zadorozhnaya, Natalia A.; Kuznetsova, Anna O.; Kanevskiy, Mikhail Z. and Semenov, Petr B. Methane content and emission in the permafrost landscapes of western Yamal, Russian Arctic: Geosciences (Basel), 10(10), Article 412, illus. incl. 1 table, sketch maps, 45 ref., October 2020.

We present the results of studies of the methane content in soils of the active layer and underlying permafrost, as well as data on the emission of methane into the atmosphere in the dominant landscapes of typical tundra of the western coast of the Yamal Peninsula. A detailed landscape map of the study area was compiled, the dominant types of landscapes were determined, and vegetation cover was described. We determined that a high methane content is characteristic of the wet landscapes: peat bogs within the floodplains, water tracks, and lake basins. Average values of the methane content in the active layer for such landscapes varied from 2.4 to 3.5 mL (CH4)/kg, with a maximum of 9.0 mL (CH4)/kg. The distribution of methane in studied sections is characterized by an increase in its concentration with depth. This confirms the diffuse mechanism of methane transport in the active layer and emission of methane into the atmosphere. The transition zone of the upper permafrost contains 2.5-5-times more methane than the active layer and may become a significant source of methane during the anticipated permafrost degradation. Significant fluxes of methane into the atmosphere of 2.6 mg (CH4) * m-2 * h-1 are characteristic of the flooded landscapes of peat bogs, water tracks, and lake basins, which occupy approximately 45% of the typical tundra area.

DOI: 10.3390/geosciences10100412

2021024345 Rivkina, E. M. (Russian Academy of Sciences, Institute of Physicochemical and Biological Problems of Soil Science, Pushchino, Russian Federation); Fedorov-Davydov, D. G.; Zakharyuk, A. G.; Shcherbakova, V. A. and Vishnivetskaya, T. A. Free iron and iron-reducing microorganisms in permafrost and permafrost-affected soils of northeastern Siberia: Eurasian Soil Science, 53(10), p. 1455-1468, illus. incl. 4 tables, sketch map, 29 ref., October 2020.

An agreement between the content of amorphous (oxalate-extractable) iron and morphochromatic features of gley attests to the modern activity of gleyzation processes in tundra soils of the Kolyma Lowland, especially within lower parts of gentle and steep slopes. A suprapermafrost reduced gley horizon thawing out in the warmest years is considered a relic of the warmer and wetter stage of soil formation. An integrated analysis of data on the contents of mobile iron and annotated metagenomes indicates that microorganisms affiliated with the Proteobacteria phylum capable of iron reduction predominate in sediments formed under hydromorphic conditions and in modern mineral soil. In laboratory experiments, the process of microbial iron reduction was more active at 5°C than at 20°C. Therefore, it can be assumed that the majority of cultivated communities of iron-reducing bacteria have been adapted to low Arctic temperatures. Under conditions of climate warming and an increase in precipitation, permafrost temperature, and thickness of the seasonally thawed layer, iron reduction processes in the soils rich in the total iron will play an even greater role and create favorable redox conditions for the formation of methane, one of the most important greenhouse gases.

DOI: 10.1134/S1064229320100166

2021024379 Zhang, Lin (Texas A&M University Corpus Christi, Physical and Environmental Science Department, Corpus Christi, TX); Liu, Xiao; Duddleston, Khrys and Hines, Mark E. The effects of pH, temperature, and humic-like substances on anaerobic carbon degradation and methanogenesis in ombrotrophic and minerotrophic Alaskan peatlands: in Microbial biogeochemistry (Burdige, David J., editor; et al.), Aquatic Geochemistry, 26(3), p. 221-244, illus. incl. 2 tables, sketch map, 107 ref., September 2020.

Methane production usually increases from the acidic sphagnum-dominated ombrotrophic peatlands to minerotrophic ones with more neutral pH and higher coverage of vascular plants. Along this ombrotrophic-minerotrophic gradient, pH, microbial communities, and properties of dissolved organic matter in porewater all vary greatly. The hydrographic change resulted from permafrost thaw and projected global warming can potentially connect the minerotrophic and ombrotrophic sites via porewater and turn acidic bogs to minerotrophic fens. It is thus very important to investigate how the anaerobic carbon degradation processes respond to changes in fundamental factors like pH, temperature, properties of dissolved organic matter, and microbial communities resulted from such hydrographic change. In this study, one ombrotrophic (pH = 3.9) and one minerotrophic peatland site were sampled in Fairbanks, Alaska in Sep 2017 and a 42-day-period anaerobic laboratory incubation was conducted to study the changes in anaerobic carbon degradation processes including primary and secondary fermentation, methanogenesis, and acetogenesis when pH, temperature, and porewater were manipulated individually and a combination of two or three of these factors. The results suggested lowering pH would inhibit many anaerobic carbon degradation processes in the minerotrophic peatland except primary fermentation. Elevating pH in the ombrotrophic site did not stimulate its methanogen community, but primary fermentation responded better with increasing pH than with increasing temperature alone. Replacing the porewater in the minerotrophic site with that from the ombrotrophic site with high aromaticity did not inhibit methanogenesis but potentially brought in highly efficient primary fermenters. Acetoclastic methanogenesis, acetogenesis, and syntrophy only exist in the minerotrophic site but not at the ombrotrophic one. Porewater from the minerotrophic site could potentially introduce acetoclastic methanogens and syntrophs to the ombrotrophic site but would not make them active unless both pH and temperature were increased. When ground water connects ombrotrophic and minerotrophic peatlands due to thawing of permafrost, secondary fermenters and acetoclastic methanogens could be introduced to acidic bogs and cooperate efficiently to degrade the stored carbon in ombrotrophic peatlands especially under elevated temperature conditions.

DOI: 10.1007/s10498-020-09372-0

2021023946 Perryman, Clarice R. (University of New Hampshire, Department of Earth Sciences, Durham, NH); Wirsing, Jochen; Bennett, Kathryn A.; Brennick, Owen; Perry, Apryl L.; Williamson, Nicole and Ernakovich, Jessica G. Heavy metals in the Arctic; distribution and enrichment of five metals in Alaskan soils: PLos One, 2020(e0233297), illus. incl. 1 table, geol. sketch maps, 61 ref., June 3, 2020.

Metal contamination of food and water resources is a known public health issue in Arctic and sub-Arctic communities due to the proximity of many communities to mining and drilling sites. In addition, permafrost thaw may release heavy metals sequestered in previously frozen soils, potentially contaminating food and water resources by increasing the concentration of metals in freshwater, plants, and wildlife. Here we assess the enrichment of selected heavy metals in Alaskan soils by synthesizing publicly available data of soil metal concentrations. We analyzed data of soil concentrations of arsenic, chromium, mercury, nickel, and lead from over 1,000 samples available through the USGS Alaskan Geochemical Database to evaluate 1) the spatial distribution of sampling locations for soil metal analysis, 2) metal concentrations in soils from different land cover types and depths, and 3) the occurrence of soils in Alaska with elevated metal concentrations relative to other soils. We found substantial clustering of sample sites in the southwestern portion of Alaska in discontinuous and sporadic permafrost, while the continuous permafrost zone in Northern Alaska and the more populous Interior are severely understudied. Metal concentration varied by land cover type but lacked consistent patterns. Concentrations of chromium, mercury, and lead were higher in soils below 10 cm depth, however these deeper soils are under-sampled. Arsenic, chromium, mercury, nickel and lead concentrations exceeded average values for US soils by one standard deviation or more in 3.7% to 18.7% of the samples in this dataset. Our analysis highlights critical gaps that impede understanding of how heavy metals in thawing permafrost soils may become mobilized and increase exposure risk for Arctic communities.

DOI: 10.1371/journal.pone.0233297

2021023900 Liu Quanhong (Northwest Agriculture and Forestry University, College of Water Resources and Architectural Engineering, Yangling, China); Wang Zhengzhong; Li Zhanchao and Wang Yi. Transversely isotropic frost heave modeling with heat-moisture-deformation coupling: Acta Geotechnica (Berlin), 15(5), p. 1273-1287, 45 ref., May 2020. Based on Publisher-supplied data.

The transversely isotropic (TISO) constitutive and frost heave models for the freezing of fine-grained soils are more accurate than the isotropic model and simpler than the orthotropic models. First, in combination with the mesoscopic composition of freezing soils, a mechanical model for the interaction between the equivalent ice lens and the soil in frozen soils is established based on the series and parallel models in the theory of composite mechanics. Second, the TISO constitutive model together with the analytic expression of five elastic constants is provided for analysis of the freezing soils. Third, a preliminary elastoplastic model for TISO freezing soil is established based on the Hill plastic model. Fourth, the heat-moisture-deformation coupling TISO model and the hydrodynamic frost heave model are derived according to a thermodynamics equation, a soil water motion equation, and generalized Hooke's law. Synchronization and uniformity of the TISO constitutive model and the TISO frost heave model are realized for analyzing the interaction between permafrost soils and buildings. Finally, an indoor standard frost heave test and the frost heave of a prototype canal are simulated based on the above models. The numerical results indicated that the models presented in this paper accurately described the frost heave and revealed the interaction between permafrost and buildings.

DOI: 10.1007/s11440-019-00774-1

2021023869 Viezzoli, Andrea (Aarhus Geophysics, Risskov, Denmark); Manca, Giovanni and Wjins, Chris. Causes and effects of the AIP trap in AEM data: Journal of Applied Geophysics, 175, Article 103970, illus. incl. sects., 1 table, geol. sketch maps, 12 ref., April 2020.

In the presence of shallow chargeable layers and resistive basement, IP effects in AEM data can severely alter the relationship between depth and voltage measured in the receiver at a given time. The contribution of the IP currents from the shallow layers can overcome that of the downward moving EM currents. As a result, the contribution of the total currents to the entire recorded transient may effectively remain trapped in the near-surface chargeable layer, with a phenomenon we call the "AIP trap". The AEM data therefore become more sensitive to the near-surface geology. They also become more sensitive to AEM systems' altitude variations. These effects can be especially relevant for AEM systems with slow ramps, which otherwise display limited near-surface resolution. The implication is a larger range of possible applications of AEM systems to mapping of, e.g., bedrock topography, permafrost, clays in regolith, and other layers relevant to geotechnics, where these layers demonstrate some chargeability. SkyTEM 12.5 Hz data from southern Spain are particularly affected by IP in areas of conductive cover. By reducing artefacts in the resistivity models derived from inversion, modelling IP improves the prediction of depth to resistive basement within a certain range of cover thickness.

DOI: 10.1016/j.jappgeo.2020.103970

2021025710 Kirdyanov, Alexander V. (University of Cambridge, Department of Geography, Cambridge, United Kingdom); Saurer, Matthias; Siegwolf, Rolf; Knorre, Anastasia A.; Prokushkin, Anatoly S.; Churakova Sidorova, Olga V.; Fonti, Marina V. and Büntgen, Ulf. Long-term ecological consequences of forest fires in the continuous permafrost zone of Siberia: Environmental Research Letters, 15(3), Paper no. 034061, illus. incl. 1 table, 33 ref., March 2020.

Wildfires are an important factor in controlling forest ecosystem dynamics across the circumpolar boreal zone. An improved understanding of their direct and indirect, short- to long-term impacts on vegetation cover and permafrost-vegetation coupling is particularly important to predict changes in carbon, nutrient and water cycles under projected climate warming. Here, we apply dendrochronological techniques on a multi-parameter dataset to reconstruct the effect of wildfires on tree growth and seasonal permafrost thaw depth in Central Siberia. Based on annually-resolved and absolutely dated information from 19 Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees and active soil layer thickness measurements, we find substantial stand-level die-off, as well as the removal of ground vegetation and the organic layer following a major wildfire in 1896. Reduced stem growth coincides with increased d 13C in the cellulose of the surviving trees during the first decade after the wildfire, when stomatal conductance was reduced. The next six to seven decades are characterized by increased permafrost active soil layer thickness. During this period of post-wildfire ecosystem recovery, enhanced tree growth together with positive d13C and negative d18O trends are indicative of higher rates of photosynthesis and improved water supply. Afterwards, a thinner active soil layer leads to reduced growth because tree physiological processes become limited by summer temperature and water availability. Revealing long-term effects of forest fires on active soil layer thickness, ground vegetation composition and tree growth, this study demonstrates the importance of complex vegetation-permafrost interactions that modify the trajectory of post-fire forest recovery across much of the circumpolar boreal zone. To further quantify the influence of boreal wildfires on large-scale carbon cycle dynamics, future work should consider a wide range of tree species from different habitats in the high-northern latitudes. Copyright (Copyright) 2020 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/ab7469

2021023801 Thomazini, Andre (Federal University of Vicosa, Department of Soil Science, Vicosa, Brazil); Francelino, Marcio Rocha; Pereira, Antonio Batista; Schunemann, Adriano Luis; Mendonca, Eduardo de Sa; Michel, Roberto Ferreira Machado and Schaefer, Carlos Ernesto Goncalves Reynaud. The current response of soil thermal regime and carbon exchange of a paraglacial coastal land system in maritime Antarctica: Land Degradation & Development, 31(5), p. 655-666, illus. incl. 1 table, sketch map, 45 ref., March 2020.

Ice-free areas of maritime Antarctica (MA) are undergoing rapid environmental adjustment due to climate change because glaciers retreated. In recently deglaciated areas, sensitive indicators related to soil can be used as proxies of the transition phase from glacial to nonglacial conditions at paraglacial coastal systems. This work aims at comprehending how paraglacial coastal land systems respond to adjustment processes in highly dynamic deglaciated areas, based on net ecosystem exchange, soil temperature (ST), and soil moisture (SM) temporal series in two different vegetation communities on a paraglacial coastal land system in MA. We selected a moss community (MC) and a mixed community with mosses and lichens (MLC). MC is located on a hydromorphic area with buffered ST regime, compared with MLC, where greater SM variation range and freezing conditions were observed. MC and MLC are currently acting as an atmospheric CO2 sink. In this work, MC showed a greater capacity of CO2 uptake during measurements (711.20 g CO2 m-2). In this part of Antarctica, where a recent trend of decreasing ST occurs, less permafrost and surface land degradation, combined with enhanced carbon storage, are expected. However, in the long term, following the readjustment of the paraglacial period, thawing is expected, coupled with permafrost degradation and carbon release to the atmosphere, under the predicted warming scenario in MA. Abstract Copyright (2020), John Wiley & Sons, Ltd.

DOI: 10.1002/ldr.3479

2021026057 Borysiak, Janina (Adam Mickiewicz University, Department of Integrated Geography, Poznan, Poland); Pleskot, Krzysztof and Rachlewicz, Grzegorz. Dryas aeolian landforms in Arctic deflationary tundra, central Spitsbergen: Polish Polar Research, 41(1), p. 41-68, illus. incl. 1 table, sketch map, 96 ref., 2020.

Aeolian activity is common on ice free areas in regions with permafrost occurrence. Sparse high-Arctic tundra vegetation, modifying surface air flow and sediments transport, influences the generation of individual landforms and their assemblages. Observations were carried in central Spitsbergen (Svalbard), characterized by quasi-continental polar climate conditions with dry summers and common existence of winds velocities above loamy-sandy sediments transportation threshold. Dryas aeolian landforms created from aeolian material trapped by Dryas octopetala dwarf shrub were diagnosed. Main morphogenetic plants are accompanied by Saxifraga oppositifolia and Bistorta vivipara, rounded out with biological soil crust. Small size of semi-circular and semi-elliptic forms (0.25-0.85 m2 ) is related to low type of D. octopetala slowly growing on raised marine terraces. Aeolian sediments are characterised by low level of organic matter content. They exhibit diversified mineralogical composition resulting from variable petrography of source glacial and fluvioglacial covers. Eightpetal mountain avens are a dendroflora species composing phytocoenoses of plant communities related to the end stages of biocoenotic succession. Presented data indicate the reference environmental state for any research on plant cover response in the environment of aeolian activity during climate change.

DOI: 10.24425/ppr.2020.132569

2021026044 Bowring, Simon P. K. (Université de Versailles Saint-Quentin-en-Yvelines, Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette, France); Lauerwald, Ronny; Guenet, Bertrand; Zhu, Dan; Guimberteau, Matthieu; Regnier, Pierre; Tootchi, Ardalan; Ducharne, Agnès and Ciais, Philippe. ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport, and transformation of dissolved organic carbon from Arctic permafrost regions; Part 2, Model evaluation over the Lena River basin: Geoscientific Model Development (GMD), 13(2), p. 507-520, illus. incl. 2 tables, 24 ref., 2020.

In this second part of a two-part study, we performed a simulation of the carbon and water budget of the Lena catchment with the land surface model ORCHIDEE MICT-LEAK, enabled to simulate dissolved organic carbon (DOC) production in soils and its transport and fate in high-latitude inland waters. The model results are evaluated for their ability to reproduce the fluxes of DOC and carbon dioxide (CO2) along the soil-inland-water continuum and the exchange of CO2 with the atmosphere, including the evasion outgassing of CO2 from inland waters. We present simulation results over the years 1901-2007 and show that the model is able to broadly reproduce observed state variables and their emergent properties across a range of interacting physical and biogeochemical processes. These include (1) net primary production (NPP), respiration and riverine hydrologic amplitude, seasonality, and inter-annual variation; (2) DOC concentrations, bulk annual flow, and their volumetric attribution at the sub-catchment level; (3) high headwater versus downstream CO2 evasion, an emergent phenomenon consistent with observations over a spectrum of high-latitude observational studies. These quantities obey emergent relationships with environmental variables like air temperature and topographic slope that have been described in the literature. This gives us confidence in reporting the following additional findings: of the ~34 Tg C yr-1 left over as input to soil matter after NPP is diminished by heterotrophic respiration, 7 Tg C yr-1 is leached and transported into the aquatic system. Of this, over half (3.6 Tg C yr-1)_ is evaded from the inland water surface back into the atmosphere and the remainder (3.4 Tg C yr-1) flushed out into the Arctic Ocean, mirroring empirically derived studies. These riverine DOC exports represent ~1.5 % of NPP. DOC exported from the floodplains is dominantly sourced from recent more "labile" terrestrial production in contrast to DOC leached from the rest of the watershed with runoff and drainage, which is mostly sourced from recalcitrant soil and litter. All else equal, both historical climate change (a spring-summer warming of 1.8 °C over the catchment) and rising atmospheric CO2 (+85.6 ppm) are diagnosed from factorial simulations to contribute similar significant increases in DOC transport via primary production, although this similarity may not hold in the future.

DOI: 10.5194/gmd-13-507-2020

2021023649 Elshamy, Mohamed E. (University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK, Canada); Princz, Daniel; Sapriza-Azuri, Gonzalo; Abdelhamed, Mohamed S.; Pietroniro, Al; Wheater, Howard S. and Razavi, Saman. On the configuration and initialization of a large-scale hydrological land surface model to represent permafrost: Hydrology and Earth System Sciences (HESS), 24(1), p. 349-379, illus. incl. 4 tables, 83 ref., 2020.

Permafrost is an important feature of cold-region hydrology, particularly in river basins such as the Mackenzie River basin (MRB), and it needs to be properly represented in hydrological and land surface models (H-LSMs) built into existing Earth system models (ESMs), especially under the unprecedented climate warming trends that have been observed. Higher rates of warming have been reported in high latitudes compared to the global average, resulting in permafrost thaw with wide-ranging implications for hydrology and feedbacks to climate. The current generation of H-LSMs is being improved to simulate permafrost dynamics by allowing deep soil profiles and incorporating organic soils explicitly. Deeper soil profiles have larger hydraulic and thermal memories that require more effort to initialize. This study aims to devise a robust, yet computationally efficient, initialization and parameterization approach applicable to regions where data are scarce and simulations typically require large computational resources. The study further demonstrates an upscaling approach to inform large-scale ESM simulations based on the insights gained by modelling at small scales. We used permafrost observations from three sites along the Mackenzie River valley spanning different permafrost classes to test the validity of the approach. Results show generally good performance in reproducing present-climate permafrost properties at the three sites. The results also emphasize the sensitivity of the simulations to the soil layering scheme used, the depth to bedrock, and the organic soil properties.

DOI: 10.5194/hess-24-349-2020

2021026061 Fedorov, Alexander (Russian Academy of Sciences, Siberian Branch, Melnikov Permafrost Institute, Yakutsk, Russian Federation); Novopriezzhaya, Varvara; Fedorov, Nikolay; Konstantinov, Pavel and Samsonova, Vera. Retrospective analysis of permafrost landscape evolution in Yakutia during the Holocene warm intervals: Land (Basel), 9(11), Article 463, illus. incl. sketch map, 57 ref., 2020. This article belongs to the special issue Permafrost landscape.

The observed global warming has significant impacts on permafrost. Permafrost changes modify landscapes and cause damage to infrastructure. The main purpose of this study was to estimate permafrost temperatures and active-layer thicknesses during the Holocene intervals with significantly warmer-than-present climates-the Atlantic (5500 years BP), Subboreal (3500 years BP) and Subatlantic (1000 years BP) optimums. Estimates were obtained using the ready-to-use models derived by G.M. Feldman, as well as mathematical modeling taking account of the paleogeography of the Holocene warm intervals. The data obtained were analyzed to reveal the regional patterns of warming impacts on different permafrost landscapes. The study results will be useful in predicting future permafrost changes in response to climate warming.

DOI: 10.3390/land9110463

2021026186 Jin Huijun (Northeast Forestry University, Institute of Cold-Regions Science and Engineering, Harbin, China); Vandenberghe, Jef; Luo Dongliang; Harris, Stuart; He Ruixia; Chen Xuemei; Jin Xiaoying; Wang Qingfeng; Zhang Ze; Spektor, Valentin; Wu Qingbai and Wang Shaoling. Quaternary permafrost in China; framework and discussions: Quaternary (Basel), 3(4), Article 32, illus. incl. sketch map, 173 ref., 2020.

The framework of Quaternary permafrost in China was reconstructed for the first time on the basis of available periglacial, glacial, and other proxies. During the Early Pleistocene (2.68-0.80 Ma BP), permafrost advanced southwards to 47-50°N in northern China and possibly occurred in alpine regions in western China. During the Middle Pleistocene (800-130 ka BP), permafrost occurred extensively on the Qinghai-Tibet Plateau (QTP) and in alpine or mountainous regions of northern, western, central, and northeastern China. The Great Interglacial occurred afterward and before the Last Glaciation, but the evidence of permafrost for this period has been seldom found. Permafrost evolution of the Last Glaciation (72-19 ka BP) in China is divided into: Expansion (72-50 ka BP), degradation (50-26 ka BP), and intensive expansion during the Last Permafrost Maximum (LPMax, 26-19 ka BP) with a permafrost extent of 5.3´106-5.4´106 km2, and when major features of present permafrost took shape. Permafrost fluctuated during the Younger Dryas (12.9-11.7 ka BP). Since the Holocene, permafrost in China expanded and retreated to lesser extents, forming the current permafrost environment. The Holocene evolution of permafrost was divided into: Unstable climate but stable permafrost during the early Holocene (11.7-8.5-7.0 ka BP); permafrost degradation during the Last Permafrost Minimum (LPMin, or the Holocene Megathermal; 8.5-7.0-4.0-3.0 ka BP) and the Medieval Warm Period (MWP; 1.0-0.5 ka BP); permafrost expansion during the Neoglaciation (4.0-3.0-1.0 ka BP) and the Little Ice Age (LIA; 0.5-0.1 ka BP); and recent permafrost degradation (20th century to the present). However, this review paper only provides the framework of Quaternary permafrost in China and some preliminary discussions. Many key questions await further investigations.

DOI: 10.3390/quat3040032

2021026183 Konstantinov, Pavel (Russian Academy of Science, Siberian Branch, Melnikov Permafrost Institute, Yakutsk, Russian Federation); Zhelezniak, Mikhail; Basharin, Nikolay; Misailov, Ivan and Andreeva, Varvara. Establishment of permafrost thermal monitoring sites in east Siberia: Land (Basel), 9(12), Article 476, illus. incl. 3 tables, sketch map, 32 ref., 2020. This article belongs to the special issue Permafrost landscape.

Permafrost lies close to the surface of the day, therefore, it is able to quickly respond to modern climatic changes. Under these conditions, the goal of understanding the evolution of permafrost in the near future requires monitoring studies of the current state of permafrost and, first of all, its thermal conditions. In this work, based on the experience of many years of research at the Melnikov Permafrost Institute of Siberian Branch of the Russian Academy of Science (MPI SB RAS), methodological and technical issues of equipping experimental sites for monitoring the thermal state of permafrost in Eastern Siberia are considered. It is demonstrated that the reliability of permafrost thermal monitoring depends not only on measurement devices used but also on proper borehole system design and adequate choice of a method for active-layer thickness measurement depending on soil composition and properties. The use of protective tubes significantly lengthens the life of sensors in soils. A method of protecting the loggers from surface waters is recommended.

DOI: 10.3390/land9120476

2021023791 Lin Lu (Hohai University, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing, China); Gao Man; Liu Jintao; Wang Jiarong; Wang Shuhong; Chen Xi and Liu Hu. Understanding the effects of climate warming on streamflow and active groundwater storage in an alpine catchment; the upper Lhasa River: Hydrology and Earth System Sciences (HESS), 24(3), p. 1145-1157, illus. incl. 4 tables, 68 ref., 2020.

Climate warming is changing streamflow regimes and groundwater storage in cold alpine regions. In this study, the Yangbajain headwater catchment in the Lhasa River basin is adopted as the study area to assess streamflow changes and active groundwater storage in response to climate warming. The results show that both annual streamflow and the mean air temperature increase significantly at respective rates of about 12.30 mm per decade and 0.28 ° per decade from 1979 to 2013 in the study area. The results of gray relational analysis indicate that the air temperature acts as a primary factor for the increased streamflow. Due to climate warming, the total glacier volume has retreated by over 25 % during the past 50 years, and the areal extent of permafrost has degraded by 15.3 % over the last 20 years. Parallel comparisons with other subbasins in the Lhasa River basin indirectly reveal that the increased streamflow at the Yangbajain Station is mainly fed by the accelerated glacier retreat. Using baseflow recession analysis, we also find that the estimated groundwater storage that is comparable with the GRACE data increases significantly at rates of about 19.32 mm per decade during the abovementioned period. That is to say, as permafrost thaws, more spaces have been made available to accommodate the increasing meltwater. Finally, a large water imbalance (of more than 5.79´107 m3a-1) between the melt-derived runoff and the actual increase in runoff as well as the groundwater storage is also observed. The results from this study suggest that the impacts of glacial retreat and permafrost degradation show compound behaviors on the storage-discharge mechanism due to climate warming, and that this fundamentally affects the water supply and the mechanisms of streamflow generation and change.

DOI: 10.5194/hess-24-1145-2020

2021026185 Panin, Andrey (Russian Academy of Sciences, Institute of Geography, Moscow, Russian Federation); Borisova, Olga; Konstantinov, Evgeny; Belyaev, Yury; Eremenko, Ekaterina; Zakharov, Andrey and Sidorchuk, Aleksey. The late Quaternary evolution of the upper reaches of fluvial systems in the southern East European Plain: Quaternary (Basel), 3(4), Article 31, illus. incl. sect., sketch map, 78 ref., 2020.

Networks of dry valleys (or balkas) and hollows in the upper reaches of fluvial basins in extraglacial areas in the Penultimate Glaciation (Marine Isotope Stage 6-MIS 6) regions of the East European Plain demonstrate clear incision/aggradation rhythms corresponding to global glacial/interglacial climate cycles. The first phase of each incision/aggradation rhythm began after the global glacial maximum and was characterized by a cool and humid climate, permafrost and sparse vegetation, when high surface runoff and active linear erosion formed a dense network of gullies. The second phase occurred at the glacial-interglacial transition and the subsequent interglacial period with its warm and humid climate and dense vegetation. This phase was distinguished by the partial filling of fluvial forms with slopewash deposits, the transformation of gullies into dry valleys (balkas) and the subsequent stabilization of fluvial forms marked by the formation of mature soils on the sides and bottoms of balkas. The third phase of the rapid accumulation of balkas developed during the cold and dry part of the next glacial epoch, resulting in the balkas becoming shallow hollows filled in with sediments. The last full incision/aggradation rhythm occurred in the late MIS 6 to mid-MIS 2. The erosion network formed during the late MIS 6 was almost completely filled by mid-MIS 2, and its manifestation in the modern topography is limited to a network of shallow hollows in the upper parts of the fluvial systems. The modern (incomplete) incision/aggradation rhythm began in the late MIS 2 and caused the formation of the modern erosion landscape in the upper reaches of fluvial systems. This rhythm is now in the stabilization phase, and the main accumulation phase of this rhythm is still far in the future.

DOI: 10.3390/quat3040031

2021024978 Mitzscherling, Julia (GFZ German Research Centre for Geosciences, Potsdam, Germany); Horn, Fabian; Winterfeld, Maria; Mahler, Linda; Kallmeyer, Jens; Overduin, Pier P.; Schirrmeister, Lutz; Winkel, Matthias; Grigoriev, Mikhail N.; Wagner, Dirk and Liebner, Susanne. Microbial community composition and abundance after millennia of submarine permafrost warming: Biogeosciences, 16(19), p. 3941-3958, illus. incl. sketch map, 127 ref., 2019.

Warming of the Arctic led to an increase in permafrost temperatures by about 0.3°C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability, and diffusivity and could in the long term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore-offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10°C. We analysed the in situ development of bacterial abundance and community composition through total cell counts (TCCs), quantitative PCR of bacterial gene abundance, and amplicon sequencing and correlated the microbial community data with temperature, pore water chemistry, and sediment physicochemical parameters. On timescales of centuries, permafrost warming coincided with an overall decreasing microbial abundance, whereas millennia after warming microbial abundance was similar to cold onshore permafrost. In addition, the dissolved organic carbon content of all cores was lowest in submarine permafrost after millennial-scale warming. Based on correlation analysis, TCC, unlike bacterial gene abundance, showed a significant rank-based negative correlation with increasing temperature, while bacterial gene copy numbers showed a strong negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with the pore water stable isotopes d18O and dD, as well as with depth. The bacterial community showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria, which are amongst the microbial taxa that were also found to be active in other frozen permafrost environments. We suggest that, millennia after permafrost warming by over 10°C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleoenvironment and not a direct effect through warming.

DOI: 10.5194/bg-16-3941-2019

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2021026052 Duchesne, C. (Geological Survey of Canada, Ottawa, ON, Canada); Chartrand, J. and Smith, S. L. Report on 2018 field activities and collection of ground-thermal and active-layer data in the Mackenzie Corridor, Northwest Territories: Open-File Report - Geological Survey of Canada, Rep. No. 8707, 84 p., illus. incl. tables, 22 ref., 2020.

This report presents a summary of field activities conducted in 2018 in the Mackenzie corridor, north of Wrigley, N.W.T. Air temperature, ground-thermal and active-layer data acquired from permafrost monitoring sites visited in 2018 are provided in graphical and tabular format. Ground temperature records for the 2007-2018 period are also presented and indicate that permafrost is generally warming throughout the corridor and for a majority of sites, permafrost is currently warmer than the baseline established during the International Polar Year (2007-2009). The data presented provide essential baseline information that can be utilized by stakeholders and others for various purposes such as land-management activities, regulatory processes and planning of northern infrastructure.

DOI: 10.4095/321921

2021026051 Ensom, Timothy (Wilfrid Laurier University, Waterloo, ON, Canada); Kokelj, Steven V.; Morse, Peter D. and Kamo McHugh, Kelly. Permafrost ground temperature data synthesis; 2013-2019 Inuvik-Tuktoyaktuk Highway region, Northwest Territories: Open-File Report - Geological Survey of Canada, Rep. No. 8656, 13 p., illus. incl. tables, 24 ref., 2020. (NWT Open Report, No. 2019-020).

Since 2013, ground temperature cables (GTCs) have been installed along the ITH corridor, prior to and following highway construction, primarily in geotechnical boreholes drilled for the purpose of terrain stability analysis. Data collection was initially led by Government of Northwest Territories (GNWT) Department of Infrastructure and now involves additional collaborators including the Geological Survey of Canada (GSC).The objective of this joint report is to synthesize metadata and initial data associated with most of these ground temperature monitoring activities. Geotechnical data and additional contextual information for most of these monitoring sites are provided by Ensom et al. (2019). The principal investigators include the Northwest Territories Geological Survey (NTGS), Dr. Peter Morse of the GSC, and GNWT Infrastructure.

DOI: 10.4095/321870

2021026050 Ensom, Timothy (Wilfrid Laurier University, Waterloo, ON, Canada); Morse, Peter D.; Kokelj, Steven V.; MacDonald, Erin; Young, Joe; Tank, Suzanne; Subedi, Rupesh; Grozic, Ed and Castagner, Ariane. Permafrost geotechnical borehole data synthesis; 2013-2017 Inuvik-Tuktoyaktuk region, Northwest Territories: Open-File Report - Geological Survey of Canada, Rep. No. 8652, 78 p., illus. incl. tables, 80 ref., 2020. (NWT Open Report, No. 2019-012).

Northwest Territories Highway 10 (140-km long), known as the Inuvik to Tuktoyaktuk Highway (ITH), traverses the Anderson Plain and Tuktoyaktuk Coastlands between Inuvik and Tuktoyaktuk over continuous permafrost. Construction began in winter 2014 following the completion of long-term environmental, socioeconomic, and engineering studies. Terrain suitability for the ITH was assessed, in part, through the analysis of sediment cores from a series of geotechnical boreholes drilled along the proposed route, and at anticipated bridge piling locations, prior to construction in 2013. Additional boreholes were drilled in winter 2017 along the ITH embankment and at undisturbed 'Sentinel' sites that represent distinct regional terrain types. The ITH opened in November 2017. This report compiles geotechnical and supporting data obtained through these projects and describes spatial variation in substrate characteristics.

DOI: 10.4095/321869

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