Permafrost Monthly Alerts (PMAs)

2022028450 Dennis, Donovan P. (Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany) and Scherler, Dirk. A combined cosmogenic nuclides approach for determining the temperature-dependence of erosion: Journal of Geophysical Research: Earth Surface, 127(4), Article e2021JF006580, illus. incl. 4 tables, 75 ref., April 2022.

Physical weathering in cold, steep bedrock hillslopes occurs at rates that are thought to depend on temperature, but our ability to quantify the temperature-dependence of erosion remains limited when integrating over geomorphic timescales. Here, we present results from a 1D numerical model of in-situ cosmogenic ¹⁰Be, ¹⁴C, and ³He concentrations that evolve as a function of erosion rate, erosion style, and ground surface temperature. We used the model to explore the suitability of these nuclides for quantifying erosion rates in areas undergoing non-steady state erosion, as well as the relationship between bedrock temperature, erosion rate, and erosional stochasticity. Our results suggest that even in stochastically eroding settings, ¹⁰Be-derived erosion rates of amalgamated samples can be used to estimate long-term erosion rates, but infrequent large events can lead to bias. The ratio of ¹⁴C to ¹⁰Be can be used to evaluate erosional stochasticity, and to determine the offset between an apparent ¹⁰Be-derived erosion rate and the long-term rate. Finally, the concentration of ³He relative to that of ¹⁰Be, and the paleothermometric interpretations derived from it, are unaffected by erosional stochasticity. These findings, discussed in the context of bedrock hillslopes in mountainous regions, indicate that the ¹⁰Be-¹⁴C-³He system in quartz offers a method to evaluate the temperature-sensitivity of bedrock erosion rates in cold, high-alpine environments. Abstract Copyright (2022), The Authors.

DOI: 10.1029/2021JF006580

2022027060 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Bogard, Matthew J.; Butman, David E.; Finlay, Kerri; Ebel, Brian; James, Jason; Johnston, Sarah Ellen; Jorgenson, M. Torre; Pastick, Neal J.; Spencer, Robert G. M.; Striegl, Robert; Walvoord, Michelle and Wickland, Kimberly P. Heterogeneous patterns of aged organic carbon export driven by hydrologic flow paths, soil texture, fire, and thaw in discontinuous permafrost headwaters: Global Biogeochemical Cycles, 36(4), Article e2021GB007242, illus. incl. 2 tables, sketch map, 94 ref., April 2022.

Climate change is thawing and potentially mobilizing vast quantities of organic carbon (OC) previously stored for millennia in permafrost soils of northern circumpolar landscapes. Climate-driven increases in fire and thermokarst may play a key role in OC mobilization by thawing permafrost and promoting transport of OC. Yet, the extent of OC mobilization and mechanisms controlling terrestrial-aquatic transfer are unclear. We demonstrate that hydrologic transport of soil dissolved OC (DOC) from the active layer and thawing permafrost to headwater streams is extremely heterogeneous and regulated by the interactions of soils, seasonal thaw, fire, and thermokarst. Repeated sampling of streams in eight headwater catchments of interior Alaska showed that the mean age of DOC for each stream ranges widely from modern to ~2,000 years B.P. Together, an endmember mixing model and nonlinear, generalized additive models demonstrated that D¹⁴C-DOC signature (and mean age) increased from spring to fall, and was proportional to hydrologic contributions from a solute-rich water source, related to presumed deeper flow paths found predominantly in silty catchments. This relationship was correlated with and mediated by catchment properties. Mean DOC ages were older in catchments with >50% burned area, indicating that fire is also an important explanatory variable. These observations underscore the high heterogeneity in aged C export and difficulty of extrapolating estimates of permafrost-derived DOC export from watersheds to larger scales. Our results provide the foundation for developing a conceptual model of permafrost DOC export necessary for advancing understanding and prediction of land-water C exchange in changing boreal landscapes. Abstract Copyright (2022), The Authors. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

DOI: 10.1029/2021GB007242

2022028445 Strand, Sarah M. (University Centre in Svalbard, Department of Arctic Geology, Longyearbyen, Norway); Christiansen, H. H. and Gilbert, G. L. Permafrost thermal dynamics and cryostratigraphy at Villum research station, Station Nord, eastern North Greenland (81°N): Journal of Geophysical Research: Earth Surface, 127(4), Article e2021JF006502, illus. incl. 1 table, sketch map, 65 ref., April 2022. Part of a special issue entitled The Arctic; an AGU joint special collection.

We provide the northernmost permafrost thermal analysis in Greenland through the ground temperature time series (2014-2021) and cryostratigraphy of two 20-m deep boreholes (SN1 and SN2) at Villum Research Station, Station Nord (81°N). Three sedimentary units are identified in the stratigraphy: glacial, glaciomarine, and beach deposits. These sandy and gravelly deposits are interpreted to comprise a deglaciation and isostatic emergence sequence. Ice-poor epigenetic permafrost grew downwards into the deposits following subaerial exposure. Relatively high salinity values (up to 70 ppt) are observed in the glaciomarine unit, resulting in freezing point depressions between 0 and -4°C. The Prinsesse Ingeborg Halvo study area has a polar tundra climate and is unique compared to other high Arctic areas because of a thick (>1 m), long-lasting snow cover. This snow cover results in relatively high permafrost temperatures for the climate and latitude and the warmest known permafrost north of 80°N. Over the seven-year study period, average 20 m permafrost temperature was -7.87°C at SN1 and -7.06°C at SN2. The warming rate at 20 m depth was 0.07°C/year at SN1 and 0.05°C/year at SN2, rates which are similar to those of other high Arctic sites. Active layer thickness, extrapolated from the temperature measurements, varied between 0.5 and 1.16 m. The interplay between snow dynamics and seasonal air temperature controls ground thermal regime in the study area. Air temperatures during autumn and midwinter, the fastest warming seasons, influence the ground thermal regime through the gradually developing, dense snowpack. Abstract Copyright (2022). The Authors.

DOI: 10.1029/2021JF006502

2022026927 Zimmer, Anais (University of Texas at Austin, Department of Geography and the Environment, Austin, TX); Beach, Timothy; Klein, Julia A. and Recharte Bullard, Jorge. The need for stewardship of lands exposed by deglaciation from climate change: Wiley Interdisciplinary Reviews. Climate Change, 13(2), Article e753, illus. incl. 1 table, 230 ref., April 2022.

Alpine glaciers worldwide will lose most of their volume by the end of the 21st century, placing alpine ecosystems and human populations at risk. The new lands that emerge from retreating glaciers provide a host of challenges for ecological and human adaptation to climate change. In these novel proglacial landscapes, ecological succession and natural hazards interplay with local agriculture, hydroelectric production, mining activities, and tourism. Research has emphasized the importance of understanding adaptation around socio-environmental systems, but regional and global management efforts that support local initiatives and connect novel proglacial landscapes to ecological, social, and cultural conservation opportunities are rare and nascent. The characteristics of these emerging lands reflect the nexus of alpine ecosystems with socio-political histories. Often overlooked in glacial-influenced systems are the interdependencies, feedbacks, and tradeoffs between these biophysical systems and local populations. There is no coordinated strategy to manage and anticipate these shifting dynamics, while affirming local practices and contexts. There is an opportunity to initiate a new conversation and co-create a governance structure around these novel landscapes and develop a new framework suitable to the Anthropocene era. This article first synthesizes the rapid socio-environmental changes that are occurring in proglacial landscapes. Second, we consider the need for integrating "bottom-up" with "top-down" approaches for the sustainable management of proglacial landscapes. Finally, we propose establishing a transdisciplinary initiative with policy-related goals to further dialogues around the governance and sustainable management of proglacial landscapes. We call for increased cooperation between actors, sectors, and regions, favoring multiscale and integrated approaches.

DOI: 10.1002/wcc.753

2022025776 Pedron, Shawn A. (University of California Irvine, Department of Earth System Science, Irvine, CA); Welker, J. M.; Euskirchen, E. S.; Klein, E. S.; Walker, J. C.; Xu, X. and Czimczik, C. I. Closing the winter gap; year-round measurements of soil CO₂ emission sources in Arctic tundra: Geophysical Research Letters, 49(6), Paper no. e2021GL097347, illus., 53 ref., March 28, 2022.

Non-growing season CO₂ emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO₂ emissions from a graminoid tundra based on year-round in situ measurements of the radiocarbon content of soil CO₂ (D¹⁴CO₂) and of bulk soil C (D¹⁴C), microbial activity, and temperature. Combining these data with land-atmosphere CO₂ exchange allows estimates of the proportion and mean age of microbial CO₂ emissions year-round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August D¹⁴CO₂ = 74 ± 4.7 ppm, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March D¹⁴CO₂ = 22 ± 1.3 ppm, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change. Abstract Copyright (2022), The Authors.

DOI: 10.1029/2021GL097347

2022025516 Cong Jinxin (Chinese Academy of Sciences, Northeast Institute of Geography and Agroecology, Key Laboratory of Wetland Ecology and Environment, Changchun, China); Gao Chuanyu; Xing Wei; Han Dongxue; Li Yunhui and Wang Guoping. Historical chemical stability of carbon pool in permafrost peatlands in northern Great Khingan Mountains (China) during the last millennium, and its paleoenvironmental implications: Catena (Giessen), 209(Part 2), Article 105853, illus. incl. 1 table, sketch map, 45 ref., February 2022.

The response of carbon pools in peatlands during the last millennium is important for global carbon cycling and is a potential indicator for paleoenvironmental research. Herein, we compared the stability and accumulation of carbon pools between the Hongtu peatland (HT, east site) and the Jintao peatland (JT, west site) in the northern Great Khingan Mountains, spanning the last 700 (HT) and 1000 (JT) years. Peat humification, aromatic and carbohydrate contents, and carbon accumulation rates in these two peat cores were analyzed to better understand the environmental impacts on the stability of carbon pools in these peatlands during the last millennium. The average carbon accumulation rates and the aromatic contents in the HT (23.09 ± 7.28 g C m^-2 yr^-1 and 28.0 ± 2.2%, respectively) and JT (23.96 ± 6.07 g C m^-2 yr^-1 and 27.8 ± 0.6%, respectively) were similar. The higher carbohydrate contents in the HT peatland than that in the JT peatland (35.8 ± 2.8% vs 27.8 ± 4.4%) indicated that the stability of carbon pools in the HT peatland were weaker than those in the JT peatland. Local precipitation and fire events may be the two major factors driving the varying stability of carbon pools in these two sites. Especially, at 250-200 cal yr BP, intense fire events may have promoted herb growth and high carbohydrate content in the accumulated plant litter, which ultimately produced higher carbohydrate and lower aromatic contents in the JT peatland than nearby periods. The paleoenvironmental conditions in the studied regions reconstructed by organic matter properties also suggested that the climate forcing mechanisms in the eastern and western sides of the northern Great Khingan Mountains were different and influenced by different degrees by the East Asian monsoon and westerlies.

DOI: 10.1016/j.catena.2021.105853

2022028336 Ma Shen (Chinese Academy of Sciences, Beiluhe Observation and Research Station on Frozen Soil Engineering and Environment in Qinghai - Tibet Plateau, Lanzhou, China); Yang Bin; Zhao Jingyi; Tan Changhai; Chen Ji; Mei Qihang and Hou Xin. Hydrothermal dynamics of seasonally frozen soil with different vegetation coverage in the Tien Shan Mountains: Frontiers in Earth Science (Lausanne), 9(806309), 12 p., illus. incl. 2 tables, 28 ref., February 1, 2022.

The hydrothermal relationship between vegetation and seasonal frozen soil is one of the key research contents in the fields of permafrost ecological environment, hydrology and climate change in alpine mountainous areas. Based on the monitoring data of air temperature, precipitation and soil hydrothermal conditions at the depth of 0-5 m from site TS-04 (with high vegetation coverage) and site TS-05 (with low vegetation coverage) in the alpine grassland of the Tianshan Mountains, this study compared and analyzed the characteristics of freezing-thawing process, temperature and moisture changes of seasonal frozen soil with different vegetation coverage. The results show that the maximum seasonal freezing depth of the two sites is almost comparable, but site TS-04 has a smaller freezing and thawing rate, and a shorter duration of freeze-thaw at all depths. TS-04 also has a smaller annual range of surface temperature and ground-air temperature difference. The analysis indicates that vegetation acts as a thermal buffer and has a good thermal insulation effect on the ground surface. Site TS-04 had high unfrozen water content in the unfrozen period and the water content increased with depth, while the unfrozen water content was low in site TS-05. In addition, the thresholds of soil water content response to rainfall events at 5 cm depth of site TS-04 and site TS-05 were 5 and 11 mm precipitation respectively, which indicated that the high vegetation coverage is conducive to rainwater infiltration, and the underlying soil of the site has a faster response to rainfall events.

DOI: 10.3389/feart.2021.806309

2022028337 Shang Yunhu (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Niu Fujun; Fang Jianhong and Wu Libo. Experimental study on thermal regime and frost jacking of pile foundation during operation period in permafrost regions: Frontiers in Earth Science (Lausanne), 10(821305), 11 p., illus. incl. 6 tables, sketch map, 35 ref., February 11, 2022.

The stability of a cast-in-place pile foundation in permafrost region is primarily subject to the thermal regime and tangential frost-heave forces (TFF) during the operation period. However, studies focusing on the thermal and mechanical characteristics of pile foundation during runtime are rare. To investigate the effect of pile foundation on the thermal regime and quantify the magnitude of unit tangential frost-heave forces (UTFF), a field experiment was conducted on the Qinghai-Tibet Plateau, China. Results showed that the cast-in-place pile foundation enhanced the heat exchange between the atmosphere and soil, which expanded the annual range of the surrounding ground temperature. Furthermore, the permafrost table depth was increased by 0.4-0.7 m (0.33-0.58 times the pile diameter). The TFF increased significantly when the soil temperature decreased from 0 to -0.5°C. Meanwhile, the thickness of the frost heaving layer was approximately double that of the active layer, in which the maximum UTFF was higher than 52.04 kPa. The adfreezing bond force of permafrost to pile shaft burdened most of the applied load, and the end bearing contributed relatively little. Findings from this study will benefit the stability maintenance and structure design of pile foundation in permafrost regions.

DOI: 10.3389/feart.2022.821305

2022027156 Dao, Thao Thi (Leibniz Universität Hannover, Institute of Soil Science, Hanover, Germany); Mikutta, Robert; Sauheitl, Leopold; Gentsch, Norman; Shibistova, Olga; Wild, Birgit; Schnecker, Jörg; Barta, Jiri; Capek, Petr; Gittel, Antje; Lashchinskiy, Nikolay; Urich, Tim; Santruckova, Hana; Richter, Andreas and Guggenberger, Georg. Lignin preservation and microbial carbohydrate metabolism in permafrost soils: Journal of Geophysical Research: Biogeosciences, 127(1), Article e2020JG006181, illus. incl. 8 tables, sketch map, 121 ref., January 2022.

Permafrost-affected soils in the northern circumpolar region store more than 1,000 Pg soil organic carbon (OC), and are strongly vulnerable to climatic warming. However, the extent to which changing soil environmental conditions with permafrost thaw affects different compounds of soil organic matter (OM) is poorly understood. Here, we assessed the fate of lignin and non-cellulosic carbohydrates in density fractionated soils (light fraction, LF vs. heavy fraction, HF) from three permafrost regions with decreasing continentality, expanding from east to west of northern Siberia (Cherskiy, Logata, Tazovskiy, respectively). In soils at the Tazovskiy site with thicker active layers, the LF showed smaller OC-normalized contents of lignin-derived phenols and plant-derived sugars and a decrease of these compounds with soil depth, while a constant or even increasing trend was observed in soils with shallower active layers (Cherskiy and Logata). Also in the HF, soils at the Tazovskiy site had smaller contents of OC-normalized lignin-derived phenols and plant-derived sugars along with more pronounced indicators of oxidative lignin decomposition and production of microbial-derived sugars. Active layer deepening, thus, likely favors the decomposition of lignin and plant-derived sugars, that is, lignocelluloses, by increasing water drainage and aeration. Our study suggests that climate-induced degradation of permafrost soils may promote carbon losses from lignin and associated polysaccharides by abolishing context-specific preservation mechanisms. However, relations of OC-based lignin-derived phenols and sugars in the HF with mineralogical properties suggest that future OM transformation and carbon losses will be modulated in addition by reactive soil minerals. Abstract Copyright (2022). The Authors.

DOI: 10.1029/2020JG006181

2022028178 Shur, Yuri (University of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, AK); Fortier, Daniel; Jorgenson, M. Torre; Kanevskiy, Mikhail; Schirrmeister, Lutz; Strauss, Jens; Vasiliev, Alexander and Jones, Melissa Ward. Yedoma permafrost genesis; over 150 years of mystery and controversy: Frontiers in Earth Science (Lausanne), 9(757891), 21 p., illus. incl. 1 table, sketch map, 114 ref., January 12, 2022.

Since the discovery of frozen megafauna carcasses in Northern Siberia and Alaska in the early 1800s, the Yedoma phenomenon has attracted many Arctic explorers and scientists. Exposed along coastal and riverbank bluffs, Yedoma often appears as large masses of ice with some inclusions of sediment. The ground ice particularly mystified geologists and geographers, and they considered sediment within Yedoma exposures to be a secondary and unimportant component. Numerous scientists around the world tried to explain the origin of Yedoma for decades, even though some of them had never seen Yedoma in the field. The origin of massive ice in Yedoma has been attributed to buried surface ice (glaciers, snow, lake ice, and icings), intrusive ice (open system pingo), and finally to ice wedges. Proponents of the last hypothesis found it difficult to explain a vertical extent of ice wedges, which in some cases exceeds 40 m. It took over 150 years of intense debates to understand the process of ice-wedge formation occurring simultaneously (syngenetically) with soil deposition and permafrost aggregation. This understanding was based on observations of the contemporary formation of syngenetic permafrost with ice wedges on the floodplains of Arctic rivers. It initially was concluded that Yedoma was a floodplain deposit, and it took several decades of debates to understand that Yedoma is of polygenetic origin. In this paper, we discuss the history of Yedoma studies from the early 19th century until the 1980s-the period when the main hypotheses of Yedoma origin were debated and developed.

DOI: 10.3389/feart.2021.757891

2022028470 Zhao Yuxia (China University of Geosciences (Beijing), School of Engineering and Technology, Beijing, China); Liu Kangqi; Liu Hongyan and Xu Hanhua. Study on stability analysis of soil-rock-mixture slopes under freeze-thaw erosion in Greater Khingan Mountains: Lithosphere, 2022(Special 10), Article 6936421, illus. incl. 5 tables, 41 ref., 2022. Part of a special issue entitled Advances in multi-physics, multi-process and multi-scale coupling effects of lithosphere system; edited by He, M. C., et. al.

Under the action of freeze-thaw erosion, slopes in permafrost regions frequently suffer from geological disasters. The unique properties of soil-rock-mixture slopes further complicate this freeze-thaw stability problem. To study the effects of freeze-thaw erosion on the stability of soil-rock-mixture slopes, several indoor tests were first carried out on the specimens collected from the target bare slope at the K105+750~K105+850 section of the Ali River to the Kubuchun Forest Farm along National Highway 332 in permafrost regions of Greater Khingan Mountains, and then, according to the test results, damage theory, strength reduction method, Python script, and ABAQUS numerical analysis software, the slippage and safety factor of the bare slope under freeze-thaw cycles were obtained, and finally, the damage degree of freeze-thaw erosion to the bare slope was quantified. To improve the stability of bare slope in the freeze-thaw environment, the composite ecological slope protection measures of arched skeleton + three-dimensional net + grass planting were finally selected, and its feasibility is verified with the help of on-site monitoring and numerical simulation; then, the long-term freeze-thaw stability of the slope after revetment was studied. Key findings indicated that (1) the threshold between soil and rock in the target slope was 5 mm, the soil-to-rock mass and volume ratios of the slope were 55.04% : 44.96% and 69.38% : 30.62%, respectively. (2) After the 150 freeze-thaw cycles, the peak strength and elastic modulus of the specimens decreased 59.7% and 79.50%, respectively. (3) Meanwhile, the freeze-thaw damage was 0.79. (4) The slope safety factor was inversely proportional to the number of freeze-thaw cycles. The target bare slope was unstable after 150 freeze-thaw cycles, and the safety stability reduction rate was 41%. (5) Compared with the bare slope, the shallow horizontal slip of the slope after revetment decreased from 1.528 m to 4.971 cm, and the slope safety factor increased from 0.997 to 4.501, which shows that the slope protection measures are initially feasible. In addition, the numerical analysis results are consistent with the field monitoring data, and the error between the two is ≤&eq;2.01%, which proves the rationality of the numerical model established in this paper and provides data support for subsequent research.

DOI: 10.2113/2022/6936421

2022026754 Hrbacek, Filip (Masaryk University, Department of Geography, Brno, Czech Republic); Engel, Zbynek; Knazkova, Michaela and Smolikova, Jana. Effect of summer snow cover on the active layer thermal regime and thickness on CALM-S JGM site, James Ross Island, eastern Antarctic Peninsula: Catena (Giessen), 207, Article 105608, illus. incl. 2 tables, geol. sketch map, 54 ref., December 2021.

This study aims to assess the role of ephemeral snow cover on ground thermal regime and active layer thickness in two ground temperature measurement profiles on the Circumpolar Active Layer Monitoring Network - South (CALM-S) JGM site on James Ross Island, eastern Antarctic Peninsula during the high austral summer 2018. The snowstorm of 13-14 January created a snowpack of recorded depth of up to 38 cm. The snowpack remained on the study site for 12 days in total and covered 46% of its area six days after the snowfall. It directly affected ground thermal regime as indicates temperature record at snow-covered profile AWS-JGM which subsurface section was nearly 5°C colder compared to the snow-free AWS-CALM profile. The thermal insulation effect of snow cover is also reflected in the mean monthly (January) and summer (DJF) ground temperatures on AWS-JGM that decreased by ca 1.1 and 0.7°C, respectively. Summer thawing degree days at a depth of 5 cm decreased by ca 10% and active layer was ca 5-10 cm thinner when compared to previous snow-free summer seasons. Surveying by ground penetrating radar revealed a general active layer thinning of up to 20% in those parts of the CALM-S which were covered by snow of >20 cm depth for at least six days.

DOI: 10.1016/j.catena.2021.105608

2022026789 Liu Guimin (Lanzhou Jiaotong University, School of Environmental and Municipal Engineering, Lanzhou, China); Wu Xiaoli; Zhao Lin; Wu Tonghua; Hu Guojie; Li Ren; Qiao Yongping and Wu Xiaodong. Soil water content in permafrost regions exhibited smaller interannual changes than non-permafrost regions during 1986-2016 on the Qinghai-Tibetan Plateau: Catena (Giessen), 207, Article 105668, illus. incl. 4 tables, geol. sketch map, 60 ref., December 2021.

Permafrost is an important factor affecting soil hydrology in cold regions, while the effects of permafrost on temporal changes in soil water content largely remain unknown. Here, based on the calibrated Climate Change Initiative (CCI) soil moisture products using field observation soil water data at 5 cm depth from 8 representative sites, we examined changing trends of climate conditions and soil water contents during 1986-2016 between the permafrost and permafrost-free sites on the Qinghai-Tibetan Plateau (QTP). We found that all the sites have been experienced continuous warming during this period. Soil water contents showed significant increasing or decreasing trends at three of the four permafrost-free sites, but there were no significant increasing or decreasing changes at all the four permafrost sites. In addition, the Mann-Kendall (M-K) test showed that there were 2 change-points in soil water content for the sites with the active layer thickness was about 2 m, while the sites with active layer thickness larger than 3 m and permafrost-free sites showed 3-5 change-points, indicating that the soil water contents in areas with shallower active layer showed smaller changes. The different changing trends and change-points between permafrost and permafrost-free sites were associated with the existence of permafrost and active layer thickness. Although soil water contents can be affected by many factors, our results suggested that permafrost existence can affect interannual changes in soil water contents, and permafrost degradation including increasing active layer thickness and disappearance of permafrost may decrease ecosystem resilience in the face of climate change.

DOI: 10.1016/j.catena.2021.105668

2022026765 Longhi, Alessandro (Insubria University, Department of Theoretical and Applied Sciences, Varese, Italy); Trombino, Luca and Guglielmin, Mauro. Soil micromorphology as tool for the past permafrost and paleoclimate reconstruction: Catena (Giessen), 207, Article 105628, illus. incl. 4 tables, geol. sketch map, 59 ref., December 2021.

Podzols developed on glacial and periglacial features provide the opportunity to reconstruct permafrost past limits and related paleoclimatic variations using micromorphological analysis.Analyzing 10 thin sections on 8 soils classified as Podzol in two study areas in the Central Italian Alps (Stelvio Pass area and Val Cantone area), we have been able to find different microstructures or pedofeatures (i.e., granular, platy, subangular blocky microstructures, silt cappings on coarse mineral grains) induced by processes related to permafrost conditions like gelifluction and ice lenses segregation. The type and the frequency of these micropedological traits allowed us to determine the lowest limit of past permafrost at 2228 m a.s.l. in Stelvio Pass area and 2347 m a.s.l. in Val Cantone area, respectively ca. 400 m and 330 m lower than today. Moreover, the analysis of paleoprecipitation and paleotemperature derived from various proxy data and the age of soil pedogenesis allowed us to identify four different phases of podzolization dated to: 13.5-11.5 ka (I phase), 11-9.7 ka (II phase), 9.3-8 ka (III phase), and 7.7-7.3 ka (IV phase). Reconstructed paleoprecipitation and paleotemperature of the four phases of podzolization also allowed us to determine that in Val Cantone there were two different permafrost aggradation periods that were synchronous to podzolization while in Stelvio Pass area one additional permafrost aggradation period that occurred at 7.7-7.3 ka.

DOI: 10.1016/j.catena.2021.105628

2022028335 Du Qingsong (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Li Guoyu; Chen Dun; Zhou Yu; Qi Shunshun; Wu Gang; Chai Mingtang; Tang Liyun; Jia Hailiang and Peng Wanlin. SBAS-InSAR-based analysis of surface deformation in the eastern Tianshan Mountains, China: Frontiers in Earth Science (Lausanne), 9(729454), 16 p., illus. incl. 4 tables, sketch maps, 56 ref., November 3, 2021.

Due to the unique geographical characteristics of cold alpine and high-altitude regions, glaciers, permafrost, ground ice, rock glaciers, and other periglacial geomorphology have developed with fragile habitats, and these areas are often the birthplaces of many river basins and natural hazards. With global warming and the extensive cryogenesis and physical weathering, the thermal state of permafrost and the mass balance of glaciers have been changed, and thus it can be deduced that the surface deformation is of great concern. To obtain ground subsidence or uplift over a large area to understand local surface changes, the small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technique was applied to process 89-scene of Sentinel-1A images ranging from December 25, 2017 to January 2, 2021 to obtain surface deformation for these 3 years for the eastern Tianshan Mountains, China. The surface deformation characteristics of the area were analyzed to provide a basic dataset for environmental protection policies and mitigation or reduction of natural hazards in this region, and to verify the applicability of SBAS-InSAR technology in alpine and high-altitude areas. The results show that the SBAS-InSAR technique processing with sentinel-1A dataset cannot be effectively used to acquire ground deformation in areas covered by trees, scrub/shrub, glaciers, snow, and ground ice, where the decohered phenomenon is serious. In other regions, SBAS-InSAR can effectively measure surface subsidence or uplift. Surface deformation is significant throughout the study area, with rates ranging from -70.7 to 50.8 mm/a and with an average rate of 1.1 mm/a. There are obvious regions of uplift in the northwest, northeast, and central sections of the study area, with uplift greater than 155.73 mm in 3 years, and three obvious regions of subsidence in the northeast and west sections of the study area, with subsidence of at least -125.20 mm in 3 years. The remaining areas of deformation are scattered, with smaller amounts of settlement and uplift and with an isolated and sporadic distribution. Areas with elevations of 3,150 to 4,275 m.a.s.l., slopes of 15°-50°, ad southwest, west, and northwest aspects are geologic disaster-prone regions and should receive more attention and more field monitoring. The results of this study have important implications for local environmental protection and hazard prevention.

DOI: 10.3389/feart.2021.729454

2022028064 Knoblauch, Christian (Universität Hamburg, Center for Earth System Research and Sustainability, Hamburg, Germany); Beer, Christian; Schuett, Alexander; Sauerland, Lewis; Liebner, Susanne; Steinhof, Axel; Rethemeyer, Janet; Grigoriev, Mikhail N.; Faguet, Alexey and Pfeiffer, Eva-Maria. Carbon dioxide and methane release following abrupt thaw of Pleistocene permafrost deposits in Arctic Siberia: Journal of Geophysical Research: Biogeosciences, 126(11), Article e2021JG006543, illus. incl. 1 table, 99 ref., November 2021.

The decomposition of thawing permafrost organic matter (OM) to the greenhouse gases (GHG) carbon dioxide (CO₂) and methane forms a positive feedback to global climate change. Data on in situ GHG fluxes from thawing permafrost OM are scarce and OM degradability is largely unknown, causing high uncertainties in the permafrost-carbon climate feedback. We combined in situ CO₂ and methane flux measurements at an abrupt permafrost thaw feature with laboratory incubations and dynamic modeling to quantify annual CO₂ release from thawing permafrost OM, estimate its in situ degradability and evaluate the explanatory power of incubation experiments. In July 2016 and 2019, CO₂ fluxes ranged between 0.24 and 2.6 g CO₂-C m^-2 d^-1. Methane fluxes were low, which coincided with the absence of active methanogens in the Pleistocene permafrost. CO₂ fluxes were lower three years after initial thaw after normalizing these fluxes to thawed carbon, indicating the depletion of labile carbon. Higher CO₂ fluxes from thawing Pleistocene permafrost than from Holocene permafrost indicate OM preservation for millennia and give evidence that microbial activity in the permafrost was not substantial. Short-term incubations overestimated in situ CO₂ fluxes but underestimated methane fluxes. Two independent models simulated median annual CO₂ fluxes of 160 and 184 g CO₂-C m^-2 from the thaw slump, which include 25%-31% CO₂ emissions during winter. Annual CO₂ fluxes represent 0.8% of the carbon pool thawed in the surface soil. Our results demonstrate the potential of abrupt thaw processes to transform the tundra from carbon neutral into a substantial GHG source. Abstract Copyright (2021), . The Authors.

DOI: 10.1029/2021JG006543

2022028061 Manies, Kristen L. (U. S. Geological Survey, Geology, Minerals, Energy, and Geophysics Science Center, Menlo Park, CA); Jones, Miriam C.; Waldrop, Mark P.; Leewis, Mary-Cathrine; Fuller, Christopher; Cornman, Robert S. and Hoefke, Kristen. Influence of permafrost type and site history on losses of permafrost carbon after thaw: Journal of Geophysical Research: Biogeosciences, 126(11), Article e2021JG006396, illus. incl. 3 tables, 69 ref., November 2021.

We quantified permafrost peat plateau and post-thaw carbon (C) stocks across a chronosequence in Interior Alaska to evaluate the amount of C lost with thaw. Macrofossil reconstructions revealed three stratigraphic layers of peat: (a) a base layer of fen/marsh peat, (b) peat from a forested peat plateau (with permafrost), and (c) collapse-scar bog peat (at sites where permafrost thaw has occurred). Radiocarbon dating revealed that peat initiated within the last 2,500 years and that permafrost aggraded during the Little Ice Age (ca. 250-575 years ago) and degraded within the last several decades. The timing of permafrost thaw within each feature was not related to thaw bog size. Their rate of expansion may be more influenced by local factors, such as ground ice content and subsurface water inputs. We found C losses due to thaw over the past century were up to 46% of the C available, but the absolute amount of C lost (kg m^-2) was over 50% lower than losses previously described in other Alaskan peatland chronosequences. We hypothesize that this difference stems from the process by which permafrost aggraded, with sites that formed permafrost epigenetically (significantly later than most peat accumulation) experiencing less absolute C loss with thaw than sites that formed syngenetically (simultaneously with peat accumulation). Epigenetic peat from our site had lower C:N ratios as compared to Alaskan sites that have syngenetic peat. This difference could help predict the magnitude of C loss with thaw across a range or permafrost types and histories. Abstract Copyright Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

DOI: 10.1029/2021JG006396

2022028065 Taylor, M. A. (Yale University, Yale School of the Environment, New Haven, CT); Celis, G.; Ledman, J. D.; Mauritz, M.; Natali, S. M.; Pegoraro, E. F.; Schadel, C. and Schuur, E. A. G. Experimental soil warming and permafrost thaw increase CH₄ emissions in an upland tundra ecosystem: Journal of Geophysical Research: Biogeosciences, 126(11), Article e2021JG006376, illus. incl. 4 tables, 83 ref., November 2021.

Rapid Arctic warming is causing permafrost to thaw and exposing large quantities of soil organic carbon (C) to potential decomposition. In dry upland tundra systems, subsidence from thawing permafrost can increase surface soil moisture resulting in higher methane (CH₄) emissions from newly waterlogged soils. The proportion of C released as carbon dioxide (CO₂) and CH₄ remains uncertain as previously dry landscapes transition to a thawed state, resulting in both wetter and drier microsites. To address how thaw and moisture interact to affect total C emissions, we measured CH₄ and CO₂ emissions from paired chambers across thaw and moisture gradients created by nine years of experimental soil warming in interior Alaska. Cumulative growing season (May-September) CH₄ emissions were elevated at both wetter (216.1-1,099.4 mg CH₄-C m^-2) and drier (129.7-392.3 mg CH₄-C m^-2) deeply thawed microsites relative to shallow thaw (55.6-215.7 mg CH₄-C m^-2) and increased with higher deep soil temperatures and permafrost thaw depth. Interannual variability in CH₄ emissions was driven by wet conditions in graminoid-dominated plots that generated >70% of emissions in a wet year. Shoulder season emissions were equivalent to growing season CH₄ emissions rates in the deeply thawed, warmed soils, highlighting the importance of non-growing season CH₄ emissions. Net C sink potential was reduced in deeply thawed wet plots by 4%-42%, and by 3.5%-8% in deeply thawed drier plots due to anaerobic respiration, suggesting that some dry upland tundra landscapes may transition into stronger CH₄ sources in a warming Arctic. Abstract Copyright (2021), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021JG006376

2022026677 Yuan Ganglie (Shanghai Jiao Tong University, School of Naval Architecture, Ocean and Civil Engineering , Shanghai Key Laboratory for Digital Maintenance of Buildings and Infrastructure, Shanghai, China); Che Ailan and Tang Hua. Evaluation of soil damage degree under freeze-thaw cycles through electrical measurements: Engineering Geology, 293, Article 106297, illus. incl. 1 table, 46 ref., November 2021.

In permafrost regions, roads and soil slopes experience freeze-thaw cycles annually and the soil characteristics (such as strength and conductivity) change irreversibly. Several studies have been conducted on the evaluation of soil damage using soil mechanics principles and electrical measurements. Owing to the limitations of previous studies, such as low efficiency and the inapplicability of real-time testing for assessing damages, a real-time quantitative test method for assessing the damage degree of layered soil subjected to freeze-thaw cycles based on electrical measurements is proposed. An electrical measurement device was developed for testing the electrical parameters of multilayer soil. Combined with electrical measurements, freeze-thaw cycle tests were performed. The resistivity of each layer of soil under freeze-thaw cycles was determined. Additionally, microstructural parameters of the multilayered soil were determined through computed tomography to investigate the changes in the soil microstructure during freeze-thaw cycles. The porosity and pore distribution characteristics of the multilayered soil under freeze-thaw cycles were obtained using image processing methods, such as median filter and K-means clustering. As the number of freeze-thaw cycles increased, the soil porosity increased, and the pore structure became less complex. Based on the relationship between the soil resistivity and the microstructural parameters, the soil damage mechanism was described, and a damage factor was introduced in developing the model. Furthermore, the dynamic damage process of the multilayered soil under freeze-thaw cycles was evaluated using the damage model, and the settlement was used to verify the results. And the damage model can be applied to evaluate the damage state of soil in permafrost region

DOI: 10.1016/j.enggeo.2021.106297

2022028052 Gandois, L. (Université de Toulouse, Laboratoire d'Ecologie Fonctionnelle et Environnement, Toulouse, France); Tananaev, N. I.; Prokushkin, A.; Solnyshkin, I. and Teisserenc, R. Seasonality of DOC export from a Russian subarctic catchment underlain by discontinuous permafrost, highlighted by high-frequency monitoring: Journal of Geophysical Research: Biogeosciences, 126(10), Article e2020JG006152, illus. incl. 4 tables, 97 ref., October 2021. Part of a special section entitled The Arctic; an AGU joint special collection.

Intense climate change and permafrost degradation impact northern watersheds and ultimately organic carbon transfer from terrestrial to aquatic ecosystems. We investigated the contemporary dissolved organic carbon (DOC) dynamics in a northern catchment underlain by discontinuous permafrost (Graviyka River, northern Siberia), where historical meteorological and hydrological data are available since 1936. Mean annual air temperature (MAAT), in contrast to precipitation and discharge was found to show a significant increasing trend since 1950. Using in situ sensing of fluorescent dissolved organic matter (fDOM), we estimated DOC concentrations at a high temporal frequency (1h) during 3 years (2015-2018), and calculated annual specific fluxes of 5.2-5.5 g C m² yr^-1. High DOC concentrations (above 10 mg L^-1) are sustained all year, exhibiting nearly chemostatic behavior. Nevertheless, the high-frequency survey of DOC and other water parameters revealed the seasonality of DOC origin and pathways in the watershed. The spring freshet dominates the annual export (up to 80%), but summer and autumn floods can also contribute up to 9% and 8% respectively. The high-frequency sampling was able to capture the specific dynamic of DOC concentration during spring flood (DOC peak preceding discharge, dilution during the spring freshet) and summer and autumn floods (contribution of DOC-rich, low conductivity water). These observations suggest a significant contribution of organic-rich water originating in peatlands, potentially from degrading palsas. The study demonstrates both that high-frequency sampling is essential to capture key events for DOC export, and that more long-term monitoring is urgently needed in these rapidly evolving watersheds. Abstract Copyright (2021), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020JG006152

2022028051 Rawlins, Michael A. (University of Massachusetts, Climate System Research Center, Amherst, MA); Connolly, Craig T. and McClelland, James W. Modeling terrestrial dissolved organic carbon loading to western Arctic rivers: Journal of Geophysical Research: Biogeosciences, 126(10), Article e2021JG006420, illus. incl. 4 tables, 92 ref., October 2021. Part of a special section entitled The Arctic; an AGU joint special collection.

The mobilization and land-to-ocean transfer of dissolved organic carbon (DOC) in Arctic watersheds is intricately linked with the region's climate and water cycle, and furthermore at risk of changes from climate warming and associated impacts. This study quantifies model-simulated estimates of runoff, surface and active layer leachate DOC concentrations and loadings to western Arctic rivers, specifically for basins that drain into coastal waters between and including the Yukon and Mackenzie Rivers. Model validation leverages data from other field measurements, synthesis studies, and modeling efforts. The simulations effectively quantify DOC leaching in surface and subsurface runoff and broadly capture the seasonal cycle in DOC concentration and mass loadings reported from other studies that use river-based measurements. A marked east-west gradient in simulated spring and summer DOC concentrations of 24 drainage basins on the North Slope of Alaska is captured by the modeling, consistent with independent data derived from river sampling. Simulated loadings for the Mackenzie and Yukon show reasonable agreement with estimates of DOC export for annual totals and four of the six seasonal comparisons. Nearly equivalent loading occurs to rivers which drain north to the Beaufort Sea and west to the Bering and Chukchi Seas. The modeling framework provides a basis for understanding carbon export to coastal waters and for assessing impacts of hydrological cycle intensification and permafrost thaw with ongoing warming in the Arctic. Abstract Copyright (2021), . The Authors.

DOI: 10.1029/2021JG006420

2022027937 Desyatkin, Roman (Russian Academy of Sciences, Institute of Biological Problems, Yakutsk, Russian Federation); Filippov, Nikolai; Desyatkin, Alexey; Konyushkov, Dmitry and Goryachkin, Sergey. Degradation of arable soils in central Yakutia; negative consequences of global warming for yedoma landscapes: Frontiers in Earth Science (Lausanne), 9(683730), 15 p., illus. incl. 1 table, sketch map, 58 ref., September 24, 2021.

Global warming, which is especially intensive in permafrost area of Central Yakutia, has dramatic consequences for scarce arable land resources in this region. In yedoma landscapes, intense permafrost thawing on arable fields unprotected by forest vegetation transforms the surface microtopography with the formation of residual thermokarst mounds of 6-10 m in diameter surrounded by a polygonal network of hollows of 0.3-1.5 m in depth above melting ice wedges. This process also takes place on former croplands abandoned in the recent decades because of socioeconomic reasons. It is accompanied by a significant transformation of the previously highly likely homogeneous soil cover composed of Cambic Turbic Cryosols (Sodic) into differentiated complexes of permafrost-affected Stagnic Cambisols or Calcic Solonetzes (Turbic) on the mounds and Calcic Stagnic Solonetzes (Turbic) in the microlows. Surface soil horizons on the mounds have a strongly to very strongly alkaline reaction (pH 8.5-9.5) and low organic carbon content; a wavy line of effervescence is found at a depth of 15-30 cm. Soils in the microlows have a close to neutral reaction in the upper horizons (pH 6.2-7.5); higher organic carbon content (2-3%); more pronounced textural differentiation of the profile with the formation of typical natric Btn and, in some cases, overlying eluvial E horizons; deeper (50-60 cm) line of effervescence; and clear stagnic features in the lower part of the profile. In the case of shallow embedding by ice wedge, the lowermost part of the soil in the microlow is characterized by the low bulk density because of the appearance of hollows after thawing of the ice-rich transient layer and melting of the top of ice wedges. This may be indicative of the further soil subsidence in the future and the appearance of initial thermokarst lakes within the yedoma terrain with its transformation into the alas type of landscape. Rapid thermokarst-driven development of microtopography followed by differentiation of the soil cover with increasing soil alkalinity on the microhighs and soil textural differentiation and overmoistening of deep layers in the microlows prevents the return of abandoned arable land to agriculture in yedoma landscapes.

DOI: 10.3389/feart.2021.683730

2022025461 Fan, R. (Northwest University, Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Xi'an, China); Shimada, H.; Tei, S.; Maximov, T. C. and Sugimoto, A. Oxygen isotope compositions of cellulose in earlywood of Larix cajanderi determined by water source rather than leaf water enrichment in a permafrost ecosystem, eastern Siberia: Journal of Geophysical Research: Biogeosciences, 126(9), Article e2020JG006125, illus. incl. 2 tables, 82 ref., September 2021.

The oxygen isotopic composition of tree-ring cellulose (d¹⁸O_cell) has been widely used to reconstruct historical environmental changes; however, the control factors on d¹⁸O_cell have not been fully constrained-especially in high latitudes. To evaluate the influence of metabolic processes and related environmental factors on d¹⁸O_cell, we analyzed the d¹⁸O values of soil water (1998-2015), stem water (1997-2016), leaf water (3 days in each 2014 and 2015), and tree-ring cellulose (1981-2016), on a dominant larch species (Larix cajanderi) in an eastern Siberian boreal forest. We determined that the d¹⁸O variability of water sources is dependent on the precipitation, and the ¹⁸O enrichment in leaf water is determined by relative humidity. These findings suggest that both water source uptake and leaf water enrichment processes can affect the d¹⁸O values of oxygen-containing compounds in larch trees in the study site. However, the d¹⁸O_cell (one of the end oxygen-containing products) was found dependent on water sources on which was related to the amount of summer rainfall in the previous year. This finding significantly differs from that of studies in other areas, which infer the positive correlation between d¹⁸O_cell and leaf water enrichment rather than precipitation or water sources. These differences are predominantly due to the specific conditions of high-latitude areas, such as the large seasonal d¹⁸O difference in precipitation, the existence of permafrost, and the low growth rate. Our findings contribute toward the development of tree-ring paleoclimate reconstructions-especially in eastern Siberia. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020JG006125

2022027848 Grombacher, Denys (Aarhus University, Department of Geoscience, Aarhus, Denmark); Auken, Esben; Foged, Nikolaj; Bording, Thue; Foley, Neil; Doran, Peter T.; Mikucki, Jill; Dugan, Hilary A.; Garza-Giron, Ricardo; Myers, Krista; Virginia, Ross A. and Tulaczyk, Slawek. Induced polarization effects in airborne transient electromagnetic data collected in the McMurdo Dry Valleys, Antarctica: Geophysical Journal International, 226(3), p. 1574-1583, illus. incl. 1 table, 51 ref., September 2021.

Airborne electromagnetics (EM) is a geophysical tool well suited to mapping glacial and hydrogeological structures in polar environments. This non-invasive method offers significant spatial coverage without requiring access to the ground surface, enabling the mapping of geological units to hundreds of metres depth over highly varied terrain. This method shows great potential for large-scale surveys in polar environments, as common targets such as permafrost, ice and brine-rich groundwater systems in these settings can be easily differentiated because of their significant contrasts in electrical properties. This potential was highlighted in a 2011 airborne EM survey in the McMurdo Dry Valleys that mapped the existence of a large-scale regional groundwater system in Taylor Valley. A more comprehensive airborne EM survey was flown in November 2018 to broadly map potential groundwater systems throughout the region. Data collected in this survey displayed significant perturbations from a process called induced polarization (IP), an effect that can greatly limit or prevent traditional EM workflows from producing reliable geological interpretations. Here, we present several examples of observed IP signatures over a range of conditions and detail how workflows explicitly designed to handle IP effects can produce reliable geological interpretations and data fits in these situations. Future polar EM surveys can be expected to encounter strong IP effects given the likely presence of geological materials (e.g. ice and permafrost) that can accentuate the influence of IP.

DOI: 10.1093/gji/ggab148

2022026814 Jilkova, Veronika (Czech Academy of Sciences, Biology Centre, Ceske Budejovice, Czech Republic); Devetter, Miloslav; Bryndova, Michala; Hajek, Tomas; Kotas, Petr; Lulakova, Petra; Meador, Travis; Navratilova, Dana; Saccone, Patrick and Macek, Petr. Carbon sequestration related to soil physical and chemical properties in the High Arctic: Global Biogeochemical Cycles, 35(9), Article e2020GB006877, illus. incl. 4 tables, sketch map, 71 ref., September 2021.

Arctic soils are an important reservoir of soil organic carbon (SOC) and their role in determining arctic ecosystem functioning in global carbon budgets requires closer attention. We investigated the coupling of soil properties and SOC stabilization mechanisms in high Arctic terrestrial habitats differing in vegetation cover and organic matter input. We focused on soil physical and chemical properties in glacier foreland, soil crust, dry tundra, wet tundra, and bird cliff meadow habitats on Svalbard (Norway). Concurrently, we performed physical fractionation to determine the amount of SOC stabilized by mineral associations or occlusion in macro and microaggregates. Initial stages of soil development (glacier foreland and soil crust habitats) exhibited characteristically high bulk density and pH, and low moisture and nutrient contents, whereas more developed soils (dry and wet tundra habitats) showed opposite trends. Contrastingly, bird cliff meadow showed low bulk density, intermediate moisture, and very high nutrient content. The amount of SOC stabilized by mineral associations and occlusion in aggregates generally increased with vegetation cover; hence, the more developed habitats supported higher contents of stabilized SOC. However, SOC was stabilized in aggregates even in initial stages of soil development. SOC content in most fractions correlated positively with contents of dissolved organic carbon and nitrogen, suggesting that both dissolved organic carbon and nitrogen might have provided some degree of SOC stabilization through increased formation of aggregates and suppression of microbial mineralization of soil organic matter, respectively. Our findings underscore the notion that models of SOC sequestration in the Arctic should account not only for total SOC content, but also SOC stabilization mechanisms, as represented by SOC content in respective soil fractions. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020GB006877

2022027763 Li Xinyu (Harbin Institute of Technology, School of Civil Engineering, Harbin, China); Jin Xiaoying; Wang Xinbin; Jin Huijun; Tang Liang; Li Xiaoying; He Ruixia; Li Yan; Huang Canjie and Zhang Sifan. Investigation of permafrost engineering geological environment with electrical resistivity tomography; a case study along the China-Russia crude oil pipelines: Engineering Geology, 291, Article 106237, illus. incl. sects., strat. cols., 7 tables, geol. sketch map, 56 ref., September 20, 2021.

The electrical resistivity tomography and vegetation surveys were conducted for investigating the distribution of frozen ground and other engineering geological characteristics at four representative sites (BHP, XFB, WLG, and XAZ) along the China-Russia Crude Oil Pipelines (CRCOPs) I and II. The comprehensive analysis shows that CRCOPs play an important role in forming and connecting supra-permafrost subaerial taliks and in facilitating thermokarst landforms, further accelerating permafrost degradation. The survey results indicate that on 15-29 August 2019, the permafrost base under the CRCOP at the XFB site was 21.5 m in depth, that of WLG site was 21.5 m (32.8 m at the undisturbed sites), and that of XAZ site, 37.3 m; the permafrost table of XFB site was 6.72 m (4.97 m on 20 m away from the pipeline), that of WLG site was 8.64 m (1.94 m at the undisturbed sites), and that of XAZ site was 6.72 and 3.38 m on the southern and northern slopes; the hydrothermal influences of CRCOPs extended horizontally to about 60 m away from the pipelines, but the vertical hydrothermal impacts were largely limited to about 10-15 m in depth at the BHP site in the zone of deep (>1.5 m) seasonal frost. The extent of engineering influences from the pipelines and associated engineering activities in patchy and island permafrost are evidently larger than those in seasonal frost. The sites with substantial changes are found in pipeline foundation soils underlain by warm (>-1°C; thermally unstable) and ice-rich permafrost. This study can timely help decision makers mitigate frost hazards in a proactive manner.

DOI: 10.1016/j.enggeo.2021.106237

2022027938 Monhonval, Arthur (Universite Catholique de Louvain, Earth and Life Institute, Louvain-la-Neuve, Belgium); Mauclet, Elisabeth; Pereira, Benoit; Vandeuren, Aubry; Strauss, Jens; Grosse, Guido; Schirrmeister, Lutz; Fuchs, Matthias; Kuhry, Peter and Opfergelt, Sophie. Mineral element stocks in the yedoma domain; a novel method applied to ice-rich permafrost regions: Frontiers in Earth Science (Lausanne), 9(703304), 18 p., illus. incl. 7 tables, sketch map, 110 ref., September 3, 2021.

With permafrost thaw, significant amounts of organic carbon (OC) previously stored in frozen deposits are unlocked and become potentially available for microbial mineralization. This is particularly the case in ice-rich regions such as the Yedoma domain. Excess ground ice degradation exposes deep sediments and their OC stocks, but also mineral elements, to biogeochemical processes. Interactions of mineral elements and OC play a crucial role for OC stabilization and the fate of OC upon thaw, and thus regulate carbon dioxide and methane emissions. In addition, some mineral elements are limiting nutrients for plant growth or microbial metabolic activity. A large ongoing effort is to quantify OC stocks and their lability in permafrost regions, but the influence of mineral elements on the fate of OC or on biogeochemical nutrient cycles has received less attention and there is an overall lack of mineral element content analyses for permafrost sediments. Here, we combine portable X-ray fluorescence (pXRF) with a bootstrapping technique to provide i) the first large-scale Yedoma domain Mineral Concentrations Assessment (YMCA) dataset, and ii) estimates of mineral element stocks in never thawed (since deposition) ice-rich Yedoma permafrost and previously thawed and partly refrozen Alas deposits. The pXRF method for mineral element quantification is non-destructive and offers a complement to the classical dissolution and measurement by optical emission spectrometry (ICP-OES) in solution. Using this method, mineral element concentrations (Si, Al, Fe, Ca, K, Ti, Mn, Zn, Sr and Zr) were assessed on 1,292 sediment samples from the Yedoma domain with lower analytical effort and lower costs relative to the ICP-OES method. The pXRF measured concentrations were calibrated using alkaline fusion and ICP-OES measurements on a subset of 144 samples (R2 from 0.725 to 0.996). The results highlight that i) the mineral element stock in sediments of the Yedoma domain (1,387,000 km2) is higher for Si, followed by Al, Fe, K, Ca, Ti, Mn, Zr, Sr, and Zn, and that ii) the stock in Al and Fe (598±213 and 288±104 Gt) is in the same order of magnitude as the OC stock (327-466 Gt).

DOI: 10.3389/feart.2021.703304

2022028334 Yin Guoan (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Luo Jing; Niu Fujun; Lin Zhanju and Liu Minghao. Thermal regime and variations in the island permafrost near the northern permafrost boundary in Xidatan, Qinghai-Tibet Plateau: Frontiers in Earth Science (Lausanne), 9(708630), 12 p., illus. incl. 3 tables, sketch map, 38 ref., July 19, 2021.

Although the thermal regime and degradation of permafrost on the Qinghai-Tibet Plateau (QTP) have been widely documented, little information exists regarding the island permafrost in the area. Ground temperatures were therefore measured for 8 years (2013-2020) at a permafrost island and at two contrasting sites in the Xidatan region to elucidate the permafrost in this area. Results indicate that the ground temperatures in the island permafrost were markedly higher than those at the same depth in the nearby marginal permafrost and the interior continuous permafrost. In addition, a distinct increasing trend was observed in the ground temperature of the island permafrost over the past 8 years, and warming was significantly faster in the deep soil than in the topsoil, indicating a bottom-up degradation pattern in the island permafrost. Moreover, due to the persistent increase in the thickness of the active-layer and the decrease in the depth of permafrost table, the permafrost island abruptly disappeared in 2018, which may be attributed to the anomalously high air temperatures that occurred in 2016 and 2017. The results of this study may provide references for understanding of the thermal regime and degradation process of island permafrost on the QTP.

DOI: 10.3389/feart.2021.708630

2022025390 Kristensen, Lene (Norwegian Water Resources and Energy Directorate, Trondheim, Norway); Czekirda, Justyna; Penna, Ivanna; Etzelmuller, Bernd; Nicolet, Pierrick; Pullarello, Jose Santiago; Blikra, Lars Harald; Skrede, Ingrid; Oldani, Simon and Abellan, Antonio. Movements, failure and climatic control of the Veslemannen rockslide, western Norway: Landslides, 18(6), p. 1963-1980, illus. incl. 2 tables, geol. sketch maps, 34 ref., June 2021.

On September 5, 2019, the Veslemannen unstable rock slope (54,000 m³) in Romsdalen, Western Norway, failed catastrophically after 5 years of continuous monitoring. During this period, the rock slope weakened while the precursor movements increased progressively, in particular from 2017. Measured displacement prior to the failure was around 19 m in the upper parts of the instability and 4-5 m in the toe area. The pre-failure movements were usually associated with precipitation events, where peak velocities occurred 2-12 h after maximum precipitation. This indicates that the pore-water pressure in the sliding zones had a large influence on the slope stability. The sensitivity to rainfall increased greatly from spring to autumn suggesting a thermal control on the pore-water pressure. Transient modelling of temperatures suggests near permafrost conditions, and deep seasonal frost was certainly present. We propose that a frozen surface layer prevented water percolation to the sliding zone during spring snowmelt and early summer rainfalls. A transition from possible permafrost to a seasonal frost setting of the landslide body after 2000 was modelled, which may have affected the slope stability. Repeated rapid accelerations during late summers and autumns caused a total of 16 events of the red (high) hazard level and evacuation of the hazard zone. Threshold values for velocity were used in the risk management when increasing or decreasing hazard levels. The inverse velocity method was initially of little value. However, in the final phase before the failure, the inverse velocity method was useful for forecasting the time of failure. Risk communication was important for maintaining public trust in early-warning systems, and especially critical is the communication of the difference between issuing the red hazard level and predicting a landslide.

DOI: 10.1007/s10346-020-01609-x

2022025388 Savvichev, Alexander (Russian Academy of Sciences, Winogradsky Institute of Microbiology, Moscow, Russian Federation); Rusanov, Igor; Dvornikov, Yury; Kadnikov, Vitaly; Kallistova, Anna; Veslopolova, Elena; Chetverova, Antonina; Leibman, Marina; Sigalevich, Pavel A.; Pimenov, Nikolay; Ravin, Nikolai and Khomutov, Artem. The water column of the Yamal tundra lakes as a microbial filter preventing methane emission: Biogeosciences, 18(9), p. 2791-2807, illus. incl. 4 tables, sketch maps, 80 ref., 2021.

Microbiological, molecular ecological, biogeochemical, and isotope geochemical research was carried out in four lakes of the central part of the Yamal Peninsula in the area of continuous permafrost. Two of them were large (73.6 and 118.6 ha) and deep (up to 10.6 and 12.3 m) mature lakes embedded into all geomorphological levels of the peninsula, and two others were smaller (3.2 and 4.2 ha) shallow (2.3 and 1.8 m) lakes which were formed as a result of thermokarst on constitutional (segregated) ground ice. Samples were collected in August 2019. The Yamal tundra lakes were found to exhibit high phytoplankton production (340-1200 mg C m^-2 d^-1) during the short summer season. Allochthonous and autochthonous, particulate and dissolved organic matter was deposited onto the bottom sediments, where methane was the main product of anaerobic degradation, and its content was 33-990 mmol CH₄ dm^-3. The rates of hydrogenotrophic methanogenesis appeared to be higher in the sediments of deep lakes than in those of the shallow ones. In the sediments of all lakes, Methanoregula and Methanosaeta were predominant components of the archaeal methanogenic community. Methane oxidation (1.4-9.9 mmol dm^-3 d^-1) occurred in the upper sediment layers simultaneously with methanogenesis. Methylobacter tundripaludum (family Methylococcaceae) predominated in the methanotrophic community of the sediments and the water column. The activity of methanotrophic bacteria in deep mature lakes resulted in a decrease in the dissolved methane concentration in lake water from 0.8-4.1 to 0.4 mmol CH₄ L^-1 d^-1, while in shallow thermokarst lakes the geochemical effect of methanotrophs was much less pronounced. Thus, only small, shallow Yamal lakes may contribute significantly to the overall diffusive methane emissions from the water surface during the warm summer season. The water column of large, deep lakes on Yamal acts, however, as a microbial filter preventing methane emission into the atmosphere. It can be assumed that climate warming will lead to an increase in the total area of thermokarst lakes, which will enhance the effect of methane release into the atmosphere.

DOI: 10.5194/bg-18-2791-2021

2022026533 Arp, Christopher D. (University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Jones, Benjamin M.; Hinkel, Kenneth M.; Kane, Douglas L.; Whitman, Matthew S. and Kemnitz, Richard. Recurring outburst floods from drained lakes; an emerging Arctic hazard: Frontiers in Ecology and the Environment, 18(7), p. 384-390, illus. incl. 1 table, sketch map, 26 ref., 2020.

New development in regions with rapidly changing climates may experience unforeseen hazards. Thermokarst lakes (bodies of freshwater that collect in depressions formed by thawing permafrost) cover 20% of Arctic lowlands and are naturally prone to causing catastrophic flooding. Cumulative lake drainage over time has resulted in up to 60% landscape coverage by drained thermokarst lake basins (DTLBs). Although the impacts of lake drainage on ecosystems and infrastructure have long been considered a potential hazard, these occurrences are usually viewed as one-time events. However, recent observations in northern Alaska highlight a previously unrecognized threat: annually recurring snow-dam outburst floods from DTLBs. Each winter, blowing snow fills DTLB drainage gullies, impounding meltwater in the spring and - upon snow-dam failure - releasing downstream floods. Data collected from 14 DTLBs in Alaska reveal a wide range in flood peaks, many of which exceed river flood events, providing a missing link in Arctic ecosystem hydrology. Projected snowier winters may result in even larger snow-dam outbursts from DTLBs, adding uncertainty to future risk assessments. If climate change also drives enhanced lake drainage, we predict even more sporadic and higher magnitude floods, with implications for downstream ecosystems and human infrastructure as development pushes into the Arctic lowlands.

DOI: 10.1002/fee.2175

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