Permafrost Monthly Alerts (PMAs)

2022008895 Costard, François (Université Paris-Saclay, Géosciences Paris-Saclay, Orsay, France); Gautier, Emmanuèle; Konstantinov, Pavel; Bouchard, Frederic; Séjourné, Antoine; Dupeyrat, Laure and Fedorov, Alexander. Thermal regime variability of islands in the Lena River near Yakutsk, eastern Siberia: Permafrost and Periglacial Processes, 33(1), p. 18-31, illus. incl. 2 tables, sketch map, 30 ref., March 2022.

Recent evidence has shown that Arctic regions have warmed about twice as much as elsewhere on the planet over the last few decades, and that high-latitude permafrost-periglacial processes and hydrological systems are notably responsive to rising temperatures. The aim of this paper is to report on the thermal regime of islands located along the Lena River floodplain, upstream of the city of Yakutsk (eastern Siberia). Four islands were monitored using waterproof dataloggers and continuous monitoring of frozen soil in contact with ice breakup of the Lena River. For each of these islands, we measured: (a) ground surface temperature, air and frozen soil temperatures at different depths; and (b) submersion duration during the flood. Our results show that within a zone of thick and continuous permafrost, the Lena floodplain is notably heterogeneous, with a combination of permanently and seasonally frozen islands. The ice breakups seem to have a negligible impact on the ground thermal regime. Our study confirms that relatively young (<30 years old) islands, composed of fine sand material, appear less prone to permafrost formation compared to older islands with ice-rich silty material. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.2136

2022008898 Demirel-Floyd, Cansu (University of Oklahoma, School of Geosciences, Norman, OK); Soreghan, Gerilyn S. and Elwood Madden, Megan E. Cyanobacterial weathering in warming periglacial sediments; implications for nutrient cycling and potential biosignatures: Permafrost and Periglacial Processes, 33(1), p. 63-77, illus. incl. 3 tables, 89 ref., March 2022.

The cryosphere hosts a widespread microbial community, yet microbial influences on silicate weathering have been historically neglected in cold-arid deserts. Here we investigate bioweathering by a cold-tolerant cyanobacteria (Leptolyngbya glacialis) via laboratory experiments using glaciofluvial drift sediments at 12°C, analogous to predicted future permafrost surface temperatures. Our results show threefold enhanced Si weathering rates in pre-weathered, mixed-lithology Antarctic biotic reactors compared to abiotic controls, indicating the significant influence of microbial life on weathering. Although biotic and abiotic weathering rates are similar in Icelandic sediments, neo-formed clay and Fe-(oxy)hydroxide minerals observed in association with biofilms in biotic reactors are common on Icelandic mafic minerals, similar to features observed in unprocessed Antarctic drifts. This suggests that microbes enhance weathering in systems where they must scavenge for nutrients that are not easily liberated via abiotic pathways; potential biosignatures may form in nutrient-rich systems as well. In both sediment types we also observed up to fourfold higher bicarbonate concentrations in biotic reactors relative to abiotic reactors, indicating that, as warming occurs, psychrotolerant biota will enhance bicarbonate flux to the oceans, thus stimulating carbonate deposition and providing a negative feedback to increasing atmospheric CO₂. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.2133

2022008896 Droppo, Ian G. (Environment and Climate Change Canada, Burlington, ON, Canada); Cenzo, Peter; McFadyen, Renee and Reid, Thomas. Assessment of the sediment and associated nutrient/contaminant continuum, from permafrost thaw slump scars to tundra lakes in the western Canadian Arctic: Permafrost and Periglacial Processes, 33(1), p. 32-45, illus. incl. 2 tables, sketch map, 62 ref., March 2022.

Within the Canadian Arctic, vast areas of previously frozen sediments and carbon are being released into aquatic ecosystems via the occurrence of permafrost thaw and retrogressive thaw slumps (RTSs). While knowledge of mass wasting RTS processes are more advanced, the significance of exposed retrogressive thaw slump scars (RTSSs) at various phases of stabilization to yield additional large quantities of ecologically relevant sediment to lakes and rivers is not well constrained. Using laboratory simulation (linked rainfall and lake flow dynamics), RTS sediments were investigated to assess the sediment continuum from the terrestrial RTSSs to depositional zones within two Arctic tundra lakes. Using an estimate of 30% of the RTSS areas contributing sediment under hypothetical 20- and 100-year rainfall events, up to 598 and 997 kg hr^-1 of RTSS sediment washoff was projected respectively. Eroded particle size, regardless of lake or initial bulk RTSS size distribution, was dominated by individual clay particles (<5 mm) that were winnowed from the RTSS surface sediment. Given this is the most biogeochemical relevant fraction, it has the potential for significant ecological impact on the lakes. This deposited fine sediment was found to be very unstable with a critical shear stress for erosion close to that of the critical shear for deposition (0.05 Pa). As such, wave energy is expected to have an impact on remobilization of fine sediments and associated compounds with concomitant implications for lake-ecosystem health. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.2134

2022008894 Vasil'chuk, Yurij K. (Lomonosov Moscow State University, Geography and Geology Departments, Moscow, Russian Federation) and Budantseva, Nadine A. Holocene ice wedges of the Kolyma Lowland and January paleotemperature reconstructions based on oxygen isotope records: Permafrost and Periglacial Processes, 33(1), p. 3-17, illus. incl. 5 tables, sketch map, 76 ref., March 2022.

Ice wedges in the Holocene deposits of alases and floodplains have been studied in the Kolyma Lowland region. Most ice wedges have been found within alases dated to between 11 and 4.2 cal kyr BP, corresponding to the Greenlandian and Northgrippian stages of the Holocene. This study confirms that the greatest intensity of ice wedge growth occurred during ~10.5-6 cal kyr BP. A decrease in their growth was mainly caused by alas draining and reduced sedimentation. In the last 4-4.5 cal kyr BP (defined as the Meghalayan stage of the Holocene), ice wedges continued to grow in old alases, sometimes as a younger generation, as well as within young alases and floodplains of the Kolyma River and its tributaries. Mean January air temperatures were quite stable during the Holocene and varied usually approximately between -33 and -41°C, with a slight cooling during the Meghalayan stage. Minor variations in mean January air temperature may indicate a stability of winter climate of northern Yakutia, probably as a result of the stable influence of the Siberian anticyclone. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.2128

2022008899 Villarroel, Cristian Daniel (Complejo Universitario Islas Malvinas, Geosphere and Biosphere Research Center, San Juan, Argentina); Ortiz, Diana Agostina; Forte, Ana Paula; Beliveau, Guillermo Tamburini; Ponce, David; Imhof, Armando and López, Andrés. Internal structure of a large, complex rock glacier and its significance in hydrological and dynamic behavior; a case study in the semi-arid Andes of Argentina: Permafrost and Periglacial Processes, 33(1), p. 78-95, illus. incl. 4 tables, sketch map, 81 ref., March 2022.

This paper presents an analysis of the internal structure, hydrogeology and dynamics of a large, complex, multilobate and multiroot rock glacier combining electrical resistivity tomography (ERT), hydrochemical data and differential interferometry synthetic aperture radar (DInSAR). The rock glacier consists of a series of overlapping lobes that represent different advancing stages with different degrees of conservation. The ERT surveys characterize the active layer and the upper part of the permafrost layer, the latter showing a heterogeneous geometry and electrical resistivity values ranging from 7 to 142 kWm. Hydrochemical data argue for both the existence of different disconnected water flow pathways inside the rock glacier and the remarkable ionic concentrator effect of this landform. The horizontal displacement from October 2014 to April 2017 shows greatest magnitudes in the upper sector of both tongues, reaching speeds of up to 150 cm/year. The active frontal sector shows a displacement rate of 2-4.5 cm/year. This study contributes to knowledge of the material properties of rock glaciers, which are considered to represent important reservoirs/water resources, and their influence on the distribution of mountain permafrost, hydrology, and dynamics. Finally, to the best of our knowledge, the possible influence of the metal content of the ground on the resistivity values recorded for mountain permafrost is highlighted for the first time. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.2132

2022008897 Zhang Saize (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Niu Fujun; Wang Shi; Sun Yongning; Wang Jinchang and Dong Tianchun. Risk assessment of engineering diseases of embankment-bridge transition section for railway in permafrost regions: Permafrost and Periglacial Processes, 33(1), p. 46-62, illus. incl. 5 tables, sketch map, 69 ref., March 2022.

The embankment-bridge transition section (EBTS) is one of the zones where railway diseases occur frequently in permafrost regions. Disease risk assessment of EBTSs can provide guidance for maintenance. In this study, considering the engineering geological conditions, climate characteristics, and embankment structure types along the Qinghai-Tibet Railway (QTR) as well as based on the disease inventory of the QTR from 2010 to 2019, the logistic regression (LR), support vector machine (SVM), and combination-weight-based gay relation analysis (GRA) were used for disease risk assessment of the EBTSs along the QTR in permafrost regions. The results indicate that the LR and SVM models have a better capability for EBTS disease prediction than the GRA model, and the SVM model can select more disease samples in relatively larger regions than the LR model. Based on the SVM and LR models, the risk level of EBTSs is divided into four classes: low- (29.9%), moderate- (39.6%), high- (22.1%), and very high (8.4%) risk. Finally, we selected 272 EBTSs in high- and very-high-risk classes for key observation during the maintenance of the QTR in permafrost regions. This study provides a reference for the risk assessment of railways built in permafrost regions using data-driven methods. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.2135

2022005774 Szymanski, Wojciech (Jagiellonian University, Department of Pedology and Soil Geography, Cracow, Poland); Drewnik, Marek; Stolarczyk, Mateusz; Musielok, Lukasz; Gus-Stolarczyk, Magdalena and Skiba, Michal. Occurrence and stability of organic intercalation in clay minerals from permafrost-affected soils in the High Arctic; a case study from Spitsbergen (Svalbard): Geoderma, 408, Article 115591, illus. incl. 2 tables, sketch map, 72 ref., February 15, 2022.

Climate warming is responsible for many environmental changes in the Arctic, which lead to the decomposition of soil organic matter (SOM) and emissions of greenhouse gases from the soil into the atmosphere. Soil minerals play a crucial role in SOM stabilization. However, little is known about the occurrence and stability of organo-mineral associations in permafrost-affected soils in the Arctic. The main aims of this study were: 1) to determine the potential occurrence of SOM within interlayers of swelling clay minerals in the permafrost-affected soils in central part of Spitsbergen (Svalbard, High Arctic) and 2) to determine resistance of the intercalated SOM within the clay minerals against thermal and chemical oxidation. The obtained results indicate that 10% to 15% of organic carbon and 30% to 45% of total nitrogen occurring in the clay fraction of the Arctic permafrost-affected soils are intercalated within the swelling clay minerals. We also report that this part of SOM is highly resistant to both chemical and thermal oxidation. These findings should be taken into consideration in the refinement of climate models and in studies concerning the thawing of permafrost, SOM mineralization, and emissions of greenhouse gases from the soil into the atmosphere.

DOI: 10.1016/j.geoderma.2021.115591

2022008912 Buckel, Johannes (Technische Universität Braunschweig, Institute for Geophysics and Extraterrestrial Physics, Braunschweig, Germany); Reinosch, Eike; Voigtländer, Anne; Dietze, Michael; Bücker, Matthias; Krebs, Nora; Schroeckh, Ruben; Mäusbacher, Roland and Hördt, Andreas. Rock glacier characteristics under semiarid climate conditions in the western Nyainqentanglha Range, Tibetan Plateau: Journal of Geophysical Research: Earth Surface, 127(1), Article e2021JF006256, illus. incl. geol. sketch map, 150 ref., January 2022.

Rock glaciers are receiving increased attention as a potential source of water and indicator of climate change in periglacial landscapes. They consist of an ice-debris mixture, which creeps downslope. Although rock glaciers are a wide-spread feature on the Tibetan Plateau, characteristics such as its ice fraction are unknown as a superficial debris layer inhibits remote assessments. We investigate one rock glacier in the semiarid western Nyainqentanglha range (WNR) with a multi-method approach, which combines geophysical, geological and geomorphological field investigations with remote sensing techniques. Long-term kinematics of the rock glacier are detected by 4-year InSAR time series analysis. The ice content and the active layer are examined by electrical resistivity tomography, ground penetrating radar, and environmental seismology. Short-term activity (11-days) is captured by a seismic network. Clast analysis shows a sorting of the rock glacier's debris. The rock glacier has three zones, which are defined by the following characteristics: (a) Two predominant lithology types are preserved separately in the superficial debris patterns, (b) heterogeneous kinematics and seismic activity, and (c) distinct ice fractions. Conceptually, the studied rock glacier is discussed as an endmember of the glacier-debris-covered glacier-rock glacier continuum. This, in turn, can be linked to its location on the semiarid lee-side of the mountain range against the Indian summer monsoon. Geologically preconditioned and glacially overprinted, the studied rock glacier is suggested to be a recurring example for similar rock glaciers in the WNR. This study highlights how geology, topography and climate influence rock glacier characteristics and development. Abstract Copyright (2022), . The Authors.

DOI: 10.1029/2021JF006256

2022007365 Eberl, D. D. (349 Mountain Meadows Road, Boulder, CO). On the formation of Martian blueberries: American Mineralogist, 107(1), p. 153-155, illus., 19 ref., January 3, 2022.

The Martian blueberries, first discovered by NASA's Opportunity rover, are concretions likely formed in sediments from hydrothermal solutions resulting from bolide impact into groundwater or permafrost. Evidence for this conclusion comes from the shapes of particle size distributions measured from Opportunity photos by Royer et al. (2006, 2008). These distributions, which exhibit a unique negative skew and lognormal positive skews, fit theoretical and experimental shapes determined for minerals precipitated from solution at higher and lower levels of supersaturation, respectively. The authors of these particle size measurements suggested that the blueberries were formed by aggregation or vapor condensation from a large meteoritic impact cloud. This origin is unlikely because such an event would not have created both negative and positive skews that closely fit distribution shapes expected for mineral crystallization from solution.

DOI: 10.2138/am-2022-8167

2022005698 Zhao Dongsheng (Chinese Academy of Sciences, Institute of Geographical Sciences and Natural Resources Research, Key Laboratory of Land Surface Pattern and Simulation, Beijing, China); Zhu Yu; Wu Shaohong and Lu Qing. Simulated response of soil organic carbon density to climate change in the northern Tibet permafrost region: Geoderma, 405, Article 115455, illus. incl. 1 table, geol. sketch maps, 104 ref., January 1, 2022.

Climate warming can enhance the decomposition of soil organic matter (SOM), thereby increasing the rate of carbon release from soils. In permafrost regions, climate warming alters the nature of freeze-thaw cycles by affecting sub-surface hydrology and soil temperature, thereby impacting the decomposition of SOM. However, this process is rarely considered in projections of the long-term dynamics of soil organic carbon (SOC) on the Tibetan Plateau (TP) in response to climate change. Here, we employ the CENTURY-FTC model, which implements a freeze-thaw module in the CENTURY model, to simulate the response of top soil organic carbon density (SOCD) at 0-20 cm depth to climate change in the permafrost region of Northern Tibet. Our findings suggest that (i) the average SOCD was 2.123 kg C m^-2 in 2015; (ii) the SOCD decreased at an average rate of 0.7 ´ 10^-3 kg C m^-2 year^-1 for the period 1961-2015; and (iii) SOCD decreases spatially from south to north across Northern Tibet. Under various climate scenarios, the SOCD is projected to decrease significantly throughout northern Tibet from 2016 to 2050, with the decline being most pronounced under the representative concentration-pathway (RCP) 8.5 scenario, which projects an increase in global mean surface temperature of 4.5 °C by 2100. Superimposed on this pattern, regional differences might be driven by vegetation type, with the largest decrements occurring in southern, alpine-meadow-dominated areas and the smallest in the northern alpine desert. We propose that this declining trend will be enhanced as climate warming continues and might be amplified by the increase in freeze-thaw processes. The addition of a freeze-thaw module to the CENTURY model changes projections of SOCD change due to climate. Whereas the freeze-thaw cycle has had little impact during the baseline period, its influence is likely to increase as climate warming continues. By 2050, freeze-thaw processes are projected to contribute 3% to SOCD decline under the RCP2.6 scenario, which projects a rise in global mean surface temperature of 1.5 °C by 2100, and as much as 10% under the RCP8.5 scenario. In general, future warming is likely to result in declining SOCD throughout northern Tibet and a reduction in the capacity of alpine soils to sequester carbon.

DOI: 10.1016/j.geoderma.2021.115455

2022008624 Virkkala, Anna-Maria (Woodwell Climate Research Center, Falmouth, MA); Natali, Susan M.; Rogers, Brendan M.; Watts, Jennifer D.; Savage, Kathleen; Connon, Sara June; Mauritz, Marguerite; Schuur, Edward A. G.; Peter, Darcy; Minions, Christina; Nojeim, Julia; Commane, Roisin; Emmerton, Craig A.; Goeckede, Mathias; Helbig, Manuel; Holl, David; Iwata, Hiroki; Kobayashi, Hideki; Kolari, Pasi; López-Blanco, Efrén; Marushchak, Maija E.; Mastepanov, Mikhail; Merbold, Lutz; Parmentier, Frans-Jan W.; Peichl, Matthias; Sachs, Torsten; Sonnentag, Oliver; Ueyama, Masahito; Voigt, Carolina; Aurela, Mika; Boike, Julia; Celis, Gerardo; Chae, Namyi; Christensen, Torben R.; Bret-Harte, M. Syndonia; Dengel, Sigrid; Dolman, Han; Edgar, Colin W.; Elberling, Bo; Euskirchen, Eugenie S.; Grelle, Achim; Hatakka, Juha; Humphreys, Elyn; Jarveoja, Jarvi; Kotani, Ayumi; Kutzbach, Lars; Laurila, Tuomas; Lohila, Annalea; Mammarella, Ivan; Matsuura, Yojiro; Meyer, Gesa; Nilsson, Mats B.; Oberbauer, Steven F.; Park, Sang-Jong; Petrov, Roman; Prokushkin, Anatoly S.; Schulze, Christopher; St. Louis, Vincent L.; Tuittila, Eeva-Stiina; Tuovinen, Juha-Pekka; Quinton, William; Varlagin, Andrej; Zona, Donatella and Zyryanov, Viacheslav I. The ABCflux database; arctic-boreal CO₂ flux observations and ancillary information aggregated to monthly time steps across terrestrial ecosystems: Earth System Science Data (ESSD), 14(1), p. 179-208, illus. incl. 4 tables, sketch map, 91 ref., 2022.

Past efforts to synthesize and quantify the magnitude and change in carbon dioxide (CO₂) fluxes in terrestrial ecosystems across the rapidly warming arctic-boreal zone (ABZ) have provided valuable information but were limited in their geographical and temporal coverage. Furthermore, these efforts have been based on data aggregated over varying time periods, often with only minimal site ancillary data, thus limiting their potential to be used in large-scale carbon budget assessments. To bridge these gaps, we developed a standardized monthly database of arctic-boreal CO₂ fluxes (ABCflux) that aggregates in situ measurements of terrestrial net ecosystem CO₂ exchange and its derived partitioned component fluxes: gross primary productivity and ecosystem respiration. The data span from 1989 to 2020 with over 70 supporting variables that describe key site conditions (e.g., vegetation and disturbance type), micrometeorological and environmental measurements (e.g., air and soil temperatures), and flux measurement techniques. Here, we describe these variables, the spatial and temporal distribution of observations, the main strengths and limitations of the database, and the potential research opportunities it enables. In total, ABCflux includes 244 sites and 6309 monthly observations; 136 sites and 2217 monthly observations represent tundra, and 108 sites and 4092 observations represent the boreal biome. The database includes fluxes estimated with chamber (19% of the monthly observations), snow diffusion (3%) and eddy covariance (78%) techniques. The largest number of observations were collected during the climatological summer (June-August; 32%), and fewer observations were available for autumn (September-October; 25%), winter (December-February; 18%), and spring (March-May; 25%). ABCflux can be used in a wide array of empirical, remote sensing and modeling studies to improve understanding of the regional and temporal variability in CO₂ fluxes and to better estimate the terrestrial ABZ CO₂ budget. ABCflux is openly and freely available online.

DOI: 10.5194/essd-14-179-2022

2022007351 Elder, Clayton D. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA); Thompson, David R.; Thorpe, Andrew K.; Chandanpurkar, Hrishikesh A.; Hanke, P. J.; Hasson, Nicholas; James, Stephanie R.; Minsley, Burke J.; Pastick, Neal J.; Olefeldt, David; Walter Anthony, K. M. and Miller, Charles E. Characterizing methane emission hotspots from thawing permafrost: Global Biogeochemical Cycles, 35(12), Article e2020GB006922, illus. incl. sect., 1 table, sketch maps, 62 ref., December 2021.

Methane (CH₄) emissions from climate-sensitive ecosystems within the northern permafrost region represent a potentially large but highly uncertain source, with current estimates spanning a factor of seven (11-75 Tg CH₄ yr^-1). Accelerating permafrost thaw threatens significant increases in pan-Arctic CH₄ emissions, amplifying the permafrost carbon feedback. We used airborne imaging spectroscopy with meter-scale spatial resolution and broad coverage to identify a previously undiscovered CH₄ emission hotspot adjacent to a thermokarst lake in interior Alaska. Hotspot emissions were confined to <1% of the 10 ha lake study area. Ground-based chamber measurements confirmed average daily fluxes from the hotspot of 1,170 mg CH₄ m^-2 d^-1, with extreme daily maxima up to 24,200 mg CH₄ m^-2 d^-1. Ground-based geophysical measurements revealed thawed permafrost directly beneath the CH₄ hotspot, extending to a depth of ~15 m, indicating that the intense CH₄ emissions likely originated from recently thawed permafrost. Hotspot emissions accounted for ~40% of total diffusive CH₄ emissions from the lake study site. Combining study site findings with hotspot statistics from our 70,000 km² airborne survey across Alaska and northwestern Canada, we estimate that pan-Arctic terrestrial thermokarst hotspots currently emit 1.1 (0.1-5.2) Tg CH₄ yr^-1, or roughly 4% of the annual pan-Arctic wetland budget from just 0.01% of the northern permafrost land area. Our results suggest that significant proportions of pan-Arctic CH₄ emissions originate from disproportionately small areas of previously undetermined thermokarst emissions hotspots, and that pan-Arctic CH₄ emissions may increase non-linearly as thermokarst processes increase under a warming climate. Abstract Copyright (2021), American Geophysical Union. All Rights Reserved. California Institute of Technology. Government sponsorship acknowledged. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

DOI: 10.1029/2020GB006922

2022007353 Fang Kai (Chinese Academy of Sciences, Institute of Botany, Laboratory of Vegetation and Environmental Change, Beijing, China); Chen Leiyi; Qin Shuqi; Zhang Qiwen; Liu Xuning; Chen Pengdong and Yang Yuanhe. Mineral and climatic controls over soil organic matter stability across the Tibetan alpine permafrost region: Global Biogeochemical Cycles, 35(12), Article e2021GB007118, illus., 92 ref., December 2021.

Permafrost thaw could accelerate microbial decomposition, lead to greenhouse gases emissions into the atmosphere, and thus trigger a positive feedback to climate warming. As a key parameter reflecting the resistance of soil organic matter (SOM) to be decomposed by microorganisms, SOM stability may determine the strength of permafrost carbon (C)-climate feedback. Adequate understanding of patterns and drivers of SOM stability can thus contribute to predicting permafrost C cycle and its feedback to climate change. However, due to limited observations, it remains unknown whether biochemical selectivity or physico-chemical protection dominates SOM stability in permafrost regions. By combining large-scale soil sampling, thermal analysis and random forest model, we quantified SOM stability in the top 10 cm using thermogravimetry and differential scanning calorimetry, and explored its spatial patterns across the Tibetan alpine permafrost region. We then constructed structural equation model to evaluate the relative importance of climatic variables, edaphic properties, substrate quality, and mineral variables in regulating SOM stability over a broad geographic scale. Our results indicated that SOM stability exhibited an increasing tendency from the southeastern to northwestern plateau. The stronger SOM stability was associated with higher mineral-organic associations and more arid conditions. By contrast, substrate quality had limited effects on SOM stability. Overall, these results provide large-scale evidence for the physico-chemical protection hypothesis, highlighting the importance of considering mineral variables in Earth system models to better predict soil C dynamics across permafrost regions. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GB007118

2022007154 Wang Ping (Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources Research, Key Laboratory of Water Cycle and Related Land Surface Processes, Beijing, China); Huang Qiwei; Tang Qi; Chen Xiaolong; Yu Jingjie; Pozdniakov, Sergey P. and Wang Tianye. Increasing annual and extreme precipitation in permafrost-dominated Siberia during 1959-2018: Journal of Hydrology, 603, Article no. 126865, illus. incl. 3 tables, sketch map, 88 ref., December 2021.

Increased attention to precipitation changes in permafrost-dominated Siberia is promoted by intensified flooding under climate warming. The observed daily precipitation spanning 60 years (1959-2018) from 129 meteorological stations across the Siberian lowlands with elevations less than 500 m (50°N-70°N, 60°E-140°E) captures significant changes in both annual and extreme precipitation. For 1959-2018, the average annual precipitation over the Siberian lowlands was 428 ± 110 mm. The average annual precipitation in non-permafrost zones was approximately 458 ± 114 mm, larger than that in permafrost zones (407 ± 102 mm). Additionally, non-permafrost zones experienced greater intensities and frequencies of precipitation extremes than permafrost zones according to four extreme precipitation indices (i.e., R99p, R95p, R´5d, and R10mm). However, the rate of increase in precipitation and precipitation extremes was greater in permafrost zones than in non-permafrost zones. These results obtained from in situ observations are generally consistent with ERA5 precipitation reanalysis data. Given faster warming in permafrost than in non-permafrost zones, the rate of increase in precipitation and precipitation extremes in permafrost zones also respond more than those in non-permafrost zones. In particular, summer precipitation in permafrost zones accelerates permafrost degradation, and the release of carbon dioxide and methane from permafrost sediments is very likely to have positive feedback effects on regional temperature and precipitation increases. Our results indicate that Siberia will face risks attributable to increased precipitation and precipitation extremes in the context of climate warming, and such risks will be greater in the permafrost zones than in the non-permafrost zones.

DOI: 10.1016/j.jhydrol.2021.126865

2022005850 Xu Xiaoming (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China) and Wu Qingbai. Active layer thickness variation on the Qinghai-Tibetan Plateau; historical and projected trends: Journal of Geophysical Research: Atmospheres, 126(23), Article e2021JD034841, illus. incl. 1 table, geol. sketch maps, 100 ref., December 16, 2021.

As the buffer layer between the atmosphere and permafrost, the active layer is vulnerable to climate change. The variation in the active layer thickness (ALT) has important effects on surface energy balance, ecosystem, hydrological cycle, vegetation cover, and engineering construction in permafrost regions. The goal of this study is to discuss the active layer variation under different shared socioeconomic pathways (SSPs) for specific warming levels and to reveal the potential interactions between the ALT and the associated driving factors in typical hydrological basins. We revised the Stefan solution using the edaphic factor and the thawing index calculated by multimodel data from the Coupled Model Intercomparison Project Phase 6 to estimate the variation in the ALT. During 2015 to 2100, the ALT will increase by 14 cm (SSP1-2.6), 43 cm (SSP2-4.5), and 1.44 m (SSP5-8.5), with average increase rates of 2.5 cm/decade, 5.8 cm/decade, and 17.5 cm/decade, respectively. The rates of increase of the ALT in the Hexi Basin, Inner Basin, Mekong Basin, Yangtze Basin, and Yellow Basin are 12.6 cm/decade, 6.7 cm/decade, 5.2 cm/decade, 8.0 cm/decade, and 5 cm/decade, respectively. These results illustrate that air temperature is the primary determinant of ALT variation and normalized difference vegetation index (NDVI) and snow depth may influence the ALT change. The most significant correlations are between the ALT and NDVI in the Yangtze Basin. In different seasons, the spring snow depth has the greatest impact on the ALT in the Hexi Basin. Abstract Copyright (2021), American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021JD034841

2022007060 Krogh, Sebastian A. (University of Saskatchewan, Centre for Hydrology, Canmore, AB, Canada) and Pomeroy, John W. Simulating site-scale permafrost hydrology; sensitivity to modelling decisions and air temperature: Journal of Hydrology, 602, Article no. 126771, illus. incl. 7 tables, sketch map, 79 ref., November 2021.

To predict future hydrological cycling in permafrost-dominated regions requires consideration of complex hydrological interactions that involve cryospheric states and fluxes, and hence thermodynamics. This challenges many hydrological models, particularly those applied in the Arctic. This study presents the implementation and validation of set of algorithms representing permafrost and frozen ground dynamics, coupled into a physically based, modular, cold regions hydrological model at two tundra sites in northern Yukon Territory, Canada. Hydrological processes represented in the model include evapotranspiration, soil moisture dynamics, flow through organic and mineral terrain, ground freeze-thaw, infiltration to frozen and unfrozen soils, snowpack energy balance, and the accumulation, wind redistribution, sublimation, and canopy interception of snow. The model was able to successfully represent observed ground surface temperature, ground thaw and snow accumulation at the two sites without calibration. A sensitivity analysis of simulated ground thaw revealed that the soil properties of the upper organic layer dominated the model response; however, its performance was robust for a range of realistic physical parameters. Different modelling decisions were assessed by removing the physically based algorithms for snowpack dynamics and ground surface temperature and replacing them with empirical approaches. Results demonstrate that more physically based approaches should be pursued to reduce uncertainties in poorly monitored environments. Finally, the model was driven by three climate warming scenarios to assess the sensitivity of snow redistribution and ablation processes and ground thaw to warming temperatures. This showed great sensitivity of snow regime and soil thaw to warming, even in the cold continental climate of the northwestern Canadian Arctic. The results are pertinent to transportation infrastructure and water management in this remote, cold, sparsely gauged region where traditional approaches to hydrological prediction are not possible.

DOI: 10.1016/j.jhydrol.2021.126771

2022004379 Zhao Lin (Nanjing University of Information Science & Technology, School of Geographical Sciences, Nanjing, China); Hu Guojie; Wu Xiaodong; Wu Tonghua; Li Ren; Pang Qiangqiang; Zou Defu; Du Erji and Zhu Xiaofan. Dynamics and characteristics of soil temperature and moisture of active layer in the central Tibetan Plateau: Geoderma, 400, Article 115083, illus. incl. 6 tables, geol. sketch map, 66 ref., October 15, 2021.

Hydro-thermal characteristics of the active layer are critical during freezing-thawing cycles, causing the moisture and heat exchanges between both permafrost and atmosphere in permafrost regions. There is better understanding of these characteristics in high-latitude permafrost areas, while comparatively little is known in the middle-low latitude areas. Here, we used field monitoring data along with statistical models to quantitatively analyze the hydro-thermal dynamics of the freezing-thawing processes at the Tanggula (TGL) site in permafrost regions of Qinghai-Tibetan Plateau (QTP). This combined approach was used to examine the hydro-thermal characteristics in high-altitude permafrost regions. Our results revealed that the duration of the freezing process was much shorter than that of the thawing process. During freezing-thawing processes, the amplitude variation in soil temperature had a significant logarithmic relationship with depth. There was a significant exponential relationship between soil water content at a depth of 5 cm and monthly precipitation. The averaged energy in the active layer consumed for phase change from water to ice was 145.53 MJ/m². Finally, we analyzed the quantitative hydro-thermal characteristics and influential factors during the freezing and thawing processes; the different hydro-thermal processes occurring in high-altitude permafrost regions were compared with those in high latitude permafrost regions. Collectively, these results offer a perspective on the difference in permafrost across different region and also provide a reference for the parameterization of land surface models.

DOI: 10.1016/j.geoderma.2021.115083

2022005513 Lindner, Fabian (Ludwig Maximilian University of Munich (LMU Munich), Department of Earth and Environmental Sciences, Munich, Germany); Wassermann, Joachim and Igel, Heiner. Seasonal freeze-thaw cycles and permafrost degradation on Mt. Zugspitze (German/Austrian Alps) revealed by single-station seismic monitoring: Geophysical Research Letters, 48(18), Paper no. e2021GL094659, illus., 62 ref., September 2021.

Thawing of mountain permafrost in response to rising temperatures degrades the stability of rock walls and thereby affects infrastructure integrity in Alpine terrain. In this study, we use 15 yr of passive seismic data from a single station deployed near a known permafrost body on Mt. Zugspitze (Germany), to monitor freeze-thaw processes. The recordings reveal a persistent cultural seismic noise source, which we utilize to compute single-station cross-correlations and extract relative seismic velocity changes. We find that parts of the cross-correlations show seasonal velocity variations (»3% peak-to-peak amplitude) and a long-term velocity decrease (»0.1%/yr). Comparison with meteorological data and a previous electrical resistivity tomography study suggests that these velocity changes are caused by freeze-thaw cycles and by permafrost degradation, respectively. The results demonstrate the potential of passive seismology for permafrost monitoring and suggest that denser instrumentation will provide detailed spatio-temporal insights on permafrost dynamics in future studies. Abstract Copyright (2021), The Authors.

DOI: 10.1029/2021GL094659

2022008256 Zwieback, Simon (University of Alaska, Geophysical Institute, Fairbanks, AK). Topographic asymmetry across the Arctic: Geophysical Research Letters, 48(17), Article e2021GL094895, illus. incl. geol. sketch maps, 53 ref., September 8, 2021.

Aspect-dependent differences in steepness provide insight into the fate and formation of permafrost-affected landscapes, but the circum-Arctic distribution of topographic asymmetry remains unknown. The maps derived here add nuance to the notion that periglacial conditions promote steeper north-facing slopes. Only 20% of the area exhibits elevated north-south asymmetry, chiefly in rugged terrain. Across all moderate-relief landscapes, there is a bell-shaped trend with temperature. Steeper south-facing slopes are common in very cold and cool regions. In between, steeper north-facing slopes predominate. Despite multiple caveats, the bell-shaped trend with temperature suggests controls that vary with climatic factors, including permafrost conditions. The bell-shaped trend and observations of permafrost degradation further indicate that certain asymmetric transition-zone landscapes are predisposed to enhanced geomorphic activity in a warming climate. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GL094895

2022005403 Chiarle, Marta (Italian National Research Council, Institute of Research for Geo-hydrological Protection, Turin, Italy); Geertsema, Marten; Mortara, Giovanni and Clague, John J. Relations between climate change and mass movement; perspectives from the Canadian Cordillera and the European Alps: Global and Planetary Change, 202, Article 103499, illus. incl. 1 table, sketch map, 170 ref., July 2021.

Earth's climate is warming and will continue to warm as the century progresses. High mountains and high latitudes are experiencing the greatest warming of all regions on Earth and also are some of the most sensitive areas to climate change, in part because ecosystems and natural processes in these areas are intimately linked to the cryosphere. Evidence is mounting that warming will further reduce permafrost and snow and ice cover in high mountains, which in turn will destabilize many slopes, alter sediment delivery to streams, and change subalpine and alpine ecosystems. This paper contributes to the continuing discussion of impacts of climate change on mountain environments by comparing and discussing processes and trends in the mountains of western Canada and the European Alps. We highlight the effects of physiography and climate on physical processes occurring in the two regions. Processes of interest include landslides and debris flows induced by glacier debuttressing, alpine permafrost thaw, changes in rainfall regime, formation and sudden drainage of glacier- and moraine-dammed lakes, ice avalanches, glacier surges, and large-scale sediment transfers due to rapid deglacierization. Our analysis points out the value of integrating observations and data from different areas of the world to better understand these processes and their impacts.

DOI: 10.1016/j.gloplacha.2021.103499

2022003266 Wang Tao (China University of Mining and Technology, School of Mechanics and Civil Engineering, State Key Laboratory for Geomechanics and Deep Underground Engineering, Xuzhou, China); Peng Erxing; Xia Lijiang; Zhou Guoqing and Wang Jianzhou. Uncertainties of thermal boundaries and soil properties on permafrost table of frozen ground in Qinghai-Tibet Plateau: Journal of Rock Mechanics and Geotechnical Engineering, 13(3), p. 671-681, illus. incl. 4 tables, 54 ref., June 2021.

In the permafrost regions of the Qinghai-Tibet Plateau (QTP), the permafrost table has a significant effect on the stability of geotechnical engineering. The thermal boundaries and soil properties are the key factors affecting the permafrost table. Complex geological environments and human activities can lead to the uncertainties of thermal boundaries and soil properties. In this paper, an array of field experiments and Monte Carlo (MC) simulations of thermal boundaries and soil properties are carried out. The coefficient of variation (COV), scale of fluctuation (SOF), and autocorrelation distance (ACD) of uncertainties of thermal boundaries and soil properties are investigated. A stochastic analysis method of the probabilistic permafrost table is then proposed, and the statistical properties of permafrost table on the QTP are computed by self-compiled program. The proposed stochastic analysis method is verified with the calculated and measured temperature observations. According to the relationship between ACD and SOF for the five theoretical autocorrelation functions (ACFs), the effects of ACF, COV, and ACD of soil properties and the COV of thermal boundaries on the permafrost tables are analyzed. The results show that the effects of different ACFs of soil properties on the standard deviation (SD) of permafrost table depth are not obvious. The SD of permafrost table depth increases with time, and the larger the COVs of thermal boundaries and soil properties, the deeper the SD of permafrost table; the longer the ACD of soil properties, the shallower the SD of permafrost table. This study can provide a reference for the stability analysis of geotechnical engineering on the QTP considering the uncertainties of thermal boundaries and soil properties.

DOI: 10.1016/j.jrmge.2020.10.008

2022006687 Eymold, William K. (Sandia National Laboratories, Albuquerque, NM); Frederick, Jennifer M.; Nole, Michael; Phrampus, Benjamin J. and Wood, Warren T. Prediction of gas hydrate formation at Blake Ridge using machine learning and probabilistic reservoir simulation: Geochemistry, Geophysics, Geosystems - G³, 22(4), p. e2020GC009574, illus. incl. 3 tables, geol. sketch map, 76 ref., April 2021.

Methane hydrates are solid structures containing methane inside of a water lattice that form under low temperature and relatively high pressure. Appropriate hydrate-forming conditions exist along continental shelves or are associated with permafrost. Hydrates have garnered scientific interest via their potential as a source of natural gas and their role in the global carbon cycle. While methane hydrates have been collected in multiple diverse geographic settings, their quantities and distribution in sediments remain poorly constrained due to sparse relevant data. Using statistical and machine learning approaches, we have developed a workflow to probabilistically predict methane hydrate occurrence from local microbial methane sourcing. This approach utilizes machine-learned global maps produced by the Global Predictive Seabed Model (GPSM) as inputs for the statistical sampling software, Dakota, and multiphase reservoir simulation software, PFLOTRAN. Dakota performs Latin hypercube sampling of the GPSM-predicted values and uncertainties to generate unique sets of input parameters for 1-D PFLOTRAN simulations of gas hydrate and free gas formation resulting from methanogenesis to steady state. We ran 100 1-D simulations spanning a kilometer in depth at 5,297 locations near Blake Ridge. Masses of hydrate and free gas formed at each location were determined by integrating the predicted saturation profiles. Elevated hydrate formation is predicted to occur at depths >500 meters below sea level at this location, and is strongly associated with high seafloor total organic carbon values. We produce representative maps of expected hydrate occurrence for the study area based on multiple realizations that can be validated against geophysical observations. Abstract Copyright (2021). National Technology & Engineering solution of Sandia, LLC.

DOI: 10.1029/2020GC009574

2022006667 Soare, R. J. (Dawson College, Geography Department, Montreal, QC, Canada); Conway, S. J.; Williams, J. P.; Philippe, M.; Mc Keown, L. E.; Godin, E. and Hawkswell, J. Possible ice-wedge polygonisation in Utopia Planitia, Mars and its latitudinal gradient of distribution: Icarus, 358, Article 114208, illus. incl. 1 table, sketch map, 109 ref., April 2021. Includes appendix.

On Earth, ice complexes are commonplace landscapes amidst the continuous permafrost of coastal or near-coastal plains in the Arctic. Formed by the freeze-thaw cycling of water, ice complex features include: hummocky (thermokarstic) terrain, inflated or deflated by the presence of absence of excess ice; thermokarst lakes (i.e. excess ice that has thawed and pooled); alases (i.e. thermokarst basins emptied of water); and, ice-wedge polygons, often characterized by raised (ice-aggraded) or lowered (ice-degraded) margins relative to the polygon centres. The origin and development of these complexes is rooted in inter-or intra-glacial pulses of temperature that engender widespread thaw, meltwater distribution and migration through the soil column (sometimes to decametres of depth), and the freeze-thaw cycling of the meltwater.The possible existence of ice-rich terrain on Mars revised by the freeze-thaw cycling of water dates back to the grainy Mariner-mission photographs of the 1960s and 1970s. However, absent of regolith samples from areas where this terrain is hypothesised, attempts to validate the ice-rich hypothesis often have ended abruptly, either with spectrometric inferences of water-equivalent hydrogen to one metre or so of depth or with "looks-like", therefore "must-be" analogies derived of Earth-based ice-complexes. In the case of small-sized Martian polygons with low- and high-centres, the similarities of form between ice and sand-wedge polygons on Earth has equivocated the reach of ice-wedge hypotheses on Mars. Here, we show that: 1)The plains' terrain of our study region in Utopia Planitia (40-50°N; 100-125°E) displays a statistically-significant and positive (linear) correlation between the ratio of low-centred to high-centred polygons (lcps vs hcps) and a poleward latitude of distribution. 2)This linear correlation would be expected, in as much as ground-ice stability increases with latitude, were the shoulders of higher-latitude lcps underlain by (aggraded) ice-wedges and those of lower-latitude hcps underlain by (degraded) ice-wedges. 3)The change of polygon morphology with latitude would not be expected were the lcps and hcps underlain by sand wedges, in as much as ground-ice stability is unrelated to their aggradation or degradation. 4)Crater counts of the polygonised terrain indicate that it is less youthful than previous studies have suggested, perhaps by an order of magnitude. This attenuates the possible inconsistency between the more temperate boundary-conditions required by the formation of ice-wedge polygons and the current constraints of extreme aridity, low temperatures and low atmospheric pressure.

DOI: 10.1016/j.icarus.2020.114208

2022008310 Kuhn, McKenzie A. (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Varner, Ruth K.; Bastviken, David; Crill, Patrick; MacIntyre, Sally; Turetsky, Merritt; Anthony, Katey Walter; McGuire, Anthony D. and Olefeldt, David. BAWLD-CH₄; a comprehensive dataset of methane fluxes from boreal and arctic ecosystems: Earth System Science Data (ESSD), 13(11), p. 5151-5189, illus. incl. 2 tables, 112 ref., 2021. Includes appendix.

Methane (CH₄) emissions from the boreal and arctic region are globally significant and highly sensitive to climate change. There is currently a wide range in estimates of high-latitude annual CH₄ fluxes, where estimates based on land cover inventories and empirical CH₄ flux data or process models (bottom-up approaches) generally are greater than atmospheric inversions (top-down approaches). A limitation of bottom-up approaches has been the lack of harmonization between inventories of site-level CH₄ flux data and the land cover classes present in high-latitude spatial datasets. Here we present a comprehensive dataset of small-scale, surface CH₄ flux data from 540 terrestrial sites (wetland and non-wetland) and 1247 aquatic sites (lakes and ponds), compiled from 189 studies. The Boreal-Arctic Wetland and Lake Methane Dataset (BAWLD-CH₄) was constructed in parallel with a compatible land cover dataset, sharing the same land cover classes to enable refined bottom-up assessments. BAWLD-CH₄ includes information on site-level CH₄ fluxes but also on study design (measurement method, timing, and frequency) and site characteristics (vegetation, climate, hydrology, soil, and sediment types, permafrost conditions, lake size and depth, and our determination of land cover class). The different land cover classes had distinct CH₄ fluxes, resulting from definitions that were either based on or co-varied with key environmental controls. Fluxes of CH₄ from terrestrial ecosystems were primarily influenced by water table position, soil temperature, and vegetation composition, while CH₄ fluxes from aquatic ecosystems were primarily influenced by water temperature, lake size, and lake genesis. Models could explain more of the between-site variability in CH₄ fluxes for terrestrial than aquatic ecosystems, likely due to both less precise assessments of lake CH₄ fluxes and fewer consistently reported lake site characteristics. Analysis of BAWLD-CH₄ identified both land cover classes and regions within the boreal and arctic domain, where future studies should be focused, alongside methodological approaches. Overall, BAWLD-CH₄ provides a comprehensive dataset of CH₄ emissions from high-latitude ecosystems that are useful for identifying research opportunities, for comparison against new field data, and model parameterization or validation. BAWLD-CH₄ can be downloaded from (Kuhn et al., 2021).

DOI: 10.5194/essd-13-5151-2021

2022008272 Lakomiec, Patryk (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Holst, Jutta; Friborg, Thomas; Crill, Patrick; Rakos, Niklas; Kljun, Natascha; Olsson, Per-Ola; Eklundh, Lars; Persson, Andreas and Rinne, Janne. Field-scale CH₄ emission at a subarctic mire with heterogeneous permafrost thaw status: Biogeosciences, 18(20), p. 5811-5830, illus. incl. 9 tables, 57 ref., 2021.

The Arctic is exposed to even faster temperature changes than most other areas on Earth. Constantly increasing temperature will lead to thawing permafrost and changes in the methane (CH₄) emissions from wetlands. One of the places exposed to those changes is the Abisko-Stordalen Mire in northern Sweden, where climate and vegetation studies have been conducted since the 1970s. In our study, we analyzed field-scale methane emissions measured by the eddy covariance method at Abisko-Stordalen Mire for 3 years (2014-2016). The site is a subarctic mire mosaic of palsas, thawing palsas, fully thawed fens, and open water bodies. A bimodal wind pattern prevalent at the site provides an ideal opportunity to measure mire patches with different permafrost status with one flux measurement system. The flux footprint for westerly winds was dominated by elevated palsa plateaus, while the footprint was almost equally distributed between palsas and thawing bog-like areas for easterly winds. As these patches are exposed to the same climatic and weather conditions, we analyzed the differences in the responses of their methane emission for environmental parameters. The methane fluxes followed a similar annual cycle over the 3 study years, with a gentle rise during spring and a decrease during autumn, without emission bursts at either end of the ice-free season. The peak emission during the ice-free season differed significantly for the two mire areas with different permafrost status: the palsa mire emitted 19 mg-C m^-2 d^-1 and the thawing wet sector 40 mg-C m^-2 d^-1. Factors controlling the methane emission were analyzed using generalized linear models. The main driver for methane fluxes was peat temperature for both wind sectors. Soil water content above the water table emerged as an explanatory variable for the 3 years for western sectors and the year 2016 in the eastern sector. The water table level showed a significant correlation with methane emission for the year 2016 as well. Gross primary production, however, did not show a significant correlation with methane emissions. Annual methane emissions were estimated based on four different gap-filing methods. The different methods generally resulted in very similar annual emissions. The mean annual emission based on all models was 3.1 ± 0.3 g-C m^-2 a^-2 for the western sector and 5.5 ± 0.5 g-C m^-2 a^-1 for the eastern sector. The average annual emissions, derived from these data and a footprint climatology, were 2.7 ± 0.5 and 8.2 ± 1.5 g-C m^-2 a^-1 for the palsa and thawing surfaces, respectively. Winter fluxes were relatively high, contributing 27%-45% to the annual emissions.

DOI: 10.5194/bg-18-5811-2021

2022008309 Olefeldt, David (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Hovemyr, Mikael; Kuhn, McKenzie A.; Bastviken, David; Bohn, Theodore J.; Connolly, John; Crill, Patrick; Euskirchen, Eugénie S.; Finkelstein, Sarah A.; Genet, Hélène; Grosse, Guido; Harris, Lorna I.; Heffernan, Liam; Helbig, Manuel; Hugelius, Gustaf; Hutchins, Ryan; Juutinen, Sari; Lara, Mark J.; Malhotra, Avni; Manies, Kristen; McGuire, A. David; Natali, Susan M.; O'Donnell, Jonathan A.; Parmentier, Frans-Jan W.; Rasanen, Aleksi; Schädel, Christina; Sonnentag, Oliver; Strack, Maria; Tank, Suzanne E.; Treat, Claire; Varner, Ruth K.; Virtanen, Tarmo; Warren, Rebecca K. and Watts, Jennifer D. The Boreal-Arctic Wetland and Lake Dataset (BAWLD): Earth System Science Data (ESSD), 13(11), p. 5127-5149, illus. incl. 3 tables, 119 ref., 2021.

Methane emissions from boreal and arctic wetlands, lakes, and rivers are expected to increase in response to warming and associated permafrost thaw. However, the lack of appropriate land cover datasets for scaling field-measured methane emissions to circumpolar scales has contributed to a large uncertainty for our understanding of present-day and future methane emissions. Here we present the Boreal-Arctic Wetland and Lake Dataset (BAWLD), a land cover dataset based on an expert assessment, extrapolated using random forest modelling from available spatial datasets of climate, topography, soils, permafrost conditions, vegetation, wetlands, and surface water extents and dynamics. In BAWLD, we estimate the fractional coverage of five wetland, seven lake, and three river classes within 0.5´0.5" grid cells that cover the northern boreal and tundra biomes (17% of the global land surface). Land cover classes were defined using criteria that ensured distinct methane emissions among classes, as indicated by a co-developed comprehensive dataset of methane flux observations. In BAWLD, wetlands occupied 3.2´10^-6 km² (14% of domain) with a 95% confidence interval between 2.8 and 3.8´10⁶. Bog, fen, and permafrost bog were the most abundant wetland classes, covering ~28% each of the total wetland area, while the highest-methane-emitting marsh and tundra wetland classes occupied 5% and 12%, respectively. Lakes, defined to include all lentic open-water ecosystems regardless of size, covered 1.4´10⁶ km² (6% of domain). Low-methane-emitting large lakes (>10 km²) and glacial lakes jointly represented 78% of the total lake area, while high-emitting peatland and yedoma laks covered 18% and 4%, respectively. Small (<0.1 km²) glacial, peatland, and yedoma lakes combined covered 17% of the total lake area but contributed disproportionally to the overall spatial uncertainty in lake area with a 95% confidence interval between 0.15 and 0.38´10⁶ km². Rivers and streams were estimated to cover 0.12´10⁶ km² (0.5% of domain), of which 8% was associated with high-methane-emitting headwaters that drain organic-rich landscapes. Distinct combinations of spatially co-occurring wetland and lake classes were identified across the BAWLD domain, allowing for the mapping of "wetscapes" that have characteristic methane emission magnitudes and sensitivities to climate change at regional scales. With BAWLD, we provide a dataset which avoids double-accounting of wetland, lake, and river extents and which includes confidence intervals for each land cover class. As such, BAWLD will be suitable for many hydrological and biogeochemical modelling and upscaling efforts for the northern boreal and arctic region, in particular those aimed at improving assessments of current and future methane emissions. Data are freely available at (Olefeldt et al., 2021).

DOI: 10.5194/essd-13-5127-2021

2022008271 Pongracz, Alexandra (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Warlind, David; Miller, Paul A. and Parmentier, Frans-Jan W. Model simulations of Arctic biogeochemistry and permafrost extent are highly sensitive to the implemented snow scheme in LPJ-GUESS: Biogeosciences, 18(20), p. 5767-5787, illus. incl. 2 tables, 55 ref., 2021. Includes appendix.

The Arctic is warming rapidly, especially in winter, which is causing large-scale reductions in snow cover. Snow is one of the main controls on soil thermodynamics, and changes in its thickness and extent affect both permafrost thaw and soil biogeochemistry. Since soil respiration during the cold season potentially offsets carbon uptake during the growing season, it is essential to achieve a realistic simulation of the effect of snow cover on soil conditions to more accurately project the direction of arctic carbon-climate feedbacks under continued winter warming. The Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) dynamic vegetation model has used - up until now - a single layer snow scheme, which underestimated the insulation effect of snow, leading to a cold bias in soil temperature. To address this shortcoming, we developed and integrated a dynamic, multi-layer snow scheme in LPJ-GUESS. The new snow scheme performs well in simulating the insulation of snow at hundreds of locations across Russia compared to observations. We show that improving this single physical factor enhanced simulations of permafrost extent compared to an advanced permafrost product, where the overestimation of permafrost cover decreased from 10% to 5% using the new snow scheme. Besides soil thermodynamics, the new snow scheme resulted in a doubled winter respiration and an overall higher vegetation carbon content. This study highlights the importance of a correct representation of snow in ecosystem models to project biogeochemical processes that govern climate feedbacks. The new dynamic snow scheme is an essential improvement in the simulation of cold season processes, which reduces the uncertainty of model projections. These developments contribute to a more realistic simulation of arctic carbon-climate feedbacks.

DOI: 10.5194/bg-18-5767-2021

2022008312 Tomczyk, Aleksandra M. (Adam Mickiewicz University, Faculty of Geographical and Geological Sciences, Poznan, Poland) and Ewertowski, Marek W. Baseline data for monitoring geomorphological effects of glacier lake outburst flood; a very-high-resolution image and GIS datasets of the distal part of the Zackenberg River, northeast Greenland: Earth System Science Data (ESSD), 13(11), p. 5293-5309, illus. incl. sketch map, 75 ref., 2021.

The polar regions experience widespread transformations, such that efficient methods are needed to monitor and understand Arctic landscape changes in response to climate warming and low-frequency, high-magnitude hydrological and geomorphological events. One example of such events, capable of causing serious landscape changes, is glacier lake outburst floods. On 6 August 2017, a flood event related to glacial lake outburst affected the Zackenberg River (NE Greenland). Here, we provided a very-high-resolution dataset representing unique time series of data captured immediately before (5 August 2017), during (6 August 2017), and after (8 August 2017) the flood. Our dataset covers a 2.1 km long distal section of the Zackenberg River. The available files comprise (1) unprocessed images captured using an unmanned aerial vehicle (UAV; URL: https://doi.org/10.5281/zenodo.4495282, Tomczyk and Ewertowski, 2021a) and (2) results of structure-from-motion (SfM) processing (orthomosaics, digital elevation models, and hillshade models in a raster format), uncertainty assessments (precision maps), and effects of geomorphological mapping in vector formats (URL: https://doi.org/10.5281/zenodo.4498296, Tomczyk and Ewertowski, 2021b). Potential applications of the presented dataset include (1) assessment and quantification of landscape changes as an immediate result of a glacier lake outburst flood; (2) long-term monitoring of high-Arctic river valley development (in conjunction with other datasets); (3) establishing a baseline for quantification of geomorphological impacts of future glacier lake outburst floods; (4) assessment of geohazards related to bank erosion and debris flow development (hazards for research station infrastructure - station buildings and bridge); (5) monitoring of permafrost degradation; and (6) modelling flood impacts on river ecosystem, transport capacity, and channel stability.

DOI: 10.5194/essd-13-5293-2021

2022005372 Robson, Benjamin Aubrey (University of Bergen, Department of Geography, Bergen, Norway); Bolch, Tobias; MacDonnell, Shelley; Hölbling, Dani; Rastner, Philipp and Schaffer, Nicole. Automated detection of rock glaciers using deep learning and object-based image analysis: Remote Sensing of Environment, 250, Article no. 112033, illus. incl. 2 tables, 97 ref., December 1, 2020. Based on Publisher-supplied data.

DOI: 10.1016/j.rse.2020.112033

2022005350 Wickland, K. P. (U. S. Geological Survey, Water Resources Mission Area, Boulder, CO); Jorgenson, M. T.; Koch, J. C.; Kanevskiy, M. and Striegl, R. G. Carbon dioxide and methane flux in a dynamic Arctic tundra landscape; decadal-scale impacts of ice wedge degradation and stabilization: Geophysical Research Letters, 47(22), Article e2020GL089894, illus., 42 ref., November 28, 2020.

Ice wedge degradation is a widespread occurrence across the circumpolar Arctic causing extreme spatial heterogeneity in water distribution, vegetation, and energy balance across landscapes. These heterogeneities influence carbon dioxide (CO₂) and methane (CH₄) fluxes, yet there is little understanding of how they effect change in landscape-level carbon (C) gas flux over time. We measured CO₂ and CH₄ fluxes in an area undergoing ice wedge degradation near Prudhoe Bay, Alaska, and combined with repeat imagery analysis to estimate seasonal landscape-level C flux response to geomorphic change. Net CO₂ and CH₄ emissions changed by -25% and +42%, respectively, resulting in a 14% increase in seasonal CO₂-C equivalent emissions over 69 years as ice wedge degradation formed water-filled troughs. The dynamic ice wedge degradation/stabilization process can cause significant changes in CO₂ and CH₄ fluxes over time, and the integration of this process is important to forecasting landscape-level C fluxes in permafrost regions abundant in ice wedges. Abstract Copyright (2020), American Geophysical Union. All Rights Reserved. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

DOI: 10.1029/2020GL089894

2022005369 Zheng Guanheng (Tsinghua University, Department of Hydraulic Engineering, Beijing, China); Yang Yuting; Yang Dawen; Dafflon, Baptiste; Yi, Yonghong; Zhang Shulei; Chen, Deliang; Gao Bing; Wang Taihua; Shi Ruijie and Wu Qinghai. Remote sensing spatiotemporal patterns of frozen soil and the environmental controls over the Tibetan Plateau during 2002-2016: Remote Sensing of Environment, 247, Article no. 111927, illus. incl. 2 tables, September 15, 2020. Based on Publisher-supplied data.

DOI: 10.1016/j.rse.2020.111927

2022006575 Vasiliev, Alexander A. (Tyumen Scientific Center of Siberian Branch of Russian Academy of Sciences, Institute of the Earth's Cryosphere, Tyumen, Russian Federation); Drozdov, Dmitry S.; Gravis, Andrey G.; Malkova, Galina V.; Nyland, Kelsey E. and Streletskiy, Dmitry A. Permafrost degradation in the western Russian Arctic: Environmental Research Letters, 15(4), Article 045001, illus. incl. 1 table, geol. sketch map, 29 ref., April 2020.

The Global Climate Observing System and Global Terrestrial Observing Network have identified permafrost as an 'Essential Climate Variable,' for which ground temperature and active layer dynamics are key variables. This work presents long-term climate, and permafrost monitoring data at seven sites representative of diverse climatic and environmental conditions in the western Russian Arctic. The region of interest is experiencing some of the highest rates of permafrost degradation globally. Since 1970, mean annual air temperatures and precipitation have increased at rates from 0.05 to 0.07°C yr^-1 and 1 to 3 mm yr^-1 respectively. In response to changing climate, all seven sites examined show evidence of rapid permafrost degradation. Mean annual ground temperatures increases from 0.03 to 0.06°C yr^-1 at 10-12 m depth were observed in continuous permafrost zone. The permafrost table at all sites has lowered, up to 8 m in the discontinuous permafrost zone. Three stages of permafrost degradation are characterized for the western Russian Arctic based on the observations reported. Copyright 2020 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/ab6f12

2022005066 Mu Yanhu (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Ground Engineering, Lanzhou, China); Ma Wei; Li Guoyu; Mao Yuncheng and Liu Yongzhi. Long-term thermal and settlement characteristics of air convection embankments with and without adjacent surface water ponding in permafrost regions: Engineering Geology, 266, Article 105464, illus. incl. sketch map, 67 ref., March 5, 2020.

Surface water is an important local factor in engineering geological conditions in permafrost regions. In this paper, the impacts of surface water ponding on the long-term thermal and settlement characteristics of an air convection embankment (ACE) were investigated based on 13 years of data records from field observations along the Qinghai-Tibet Railway (QTR). The time series of the ground temperatures and the settlement of two ACEs with and without adjacent surface water ponding were investigated and compared. The results indicated that surface water ponding could significantly affect the thermal performance of the ACE. Without surface water ponding, the ACE showed a satisfactory cooling effect; the underlying permafrost table rose, and the shallow permafrost layer cooled significantly after construction of the embankment. However, with surface water ponding, the great heat capacity and latent heat of the ponded water and related capillary action impeded the thermal interaction between the ACE and the underlying permafrost. Before the drainage of the ponded water, no permafrost cooling occurred beneath the embankment. The settlement of the two ACEs also differed significantly. The creep of the ice-rich permafrost layer immediately beneath the permafrost table was inferred as the main contribution of the settlement. The temperature of the layer was the main factor determining the rate of settlement. The results can help the hydrothermal analysis of engineering foundations built over permafrost and provide a reference for embankment construction and maintenance in permafrost regions with rich surface water.

DOI: 10.1016/j.enggeo.2019.105464

2022008156 Tai Bowen (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key laboratory of Frozen Soil Engineering, Lanzhou, China); Wu Qingbai; Zhang Zhongqiong and Xu Xiaoming. Cooling performance and deformation behavior of crushed-rock embankments on the Qinghai-Tibet Railway in permafrost regions: Engineering Geology, 265, Article 105453, illus. incl. strat. cols., geol. sketch map, 49 ref., February 2020.

The structural functionality of roads and railways in warm permafrost regions is influenced by both physical and mechanical processes at work within the underlying subgrade. This paper uses ten-years worth of monitoring data to examine the thermal regimes and deformation behaviors of three different types of crushed-rock embankments employed in the construction of the Qinghai-Tibet Railway, which is located in a warm permafrost region of the Tibetan Plateau, China. More specifically, the efficiency of U-shaped crushed-rock, crushed-rock revetment, and crushed-rock basement embankments in stabilizing permafrost temperature is evaluated with consideration to the permafrost table, ground temperature, and mean annual ground temperature. Then, deformation laws in the three embankments were analyzed. Finally, deformation characteristics and sources for general subgrade are discussed and summarized on the basis of monitoring data and previous research. Results show the permafrost table of each of the three crushed-rock embankments to be higher than that of the natural ground at all times, and that the underlying permafrost warms with time regardless of the type of embankment employed. The deformation characteristics of general subgrade in permafrost regions are determined to be non-uniform and persistent. Furthermore, U-shaped crushed-rock embankment out-performed both crushed-rock revetment embankment and crushed-rock basement embankment in terms of cooling capacity and ability to weaken the sunny-shady slope effect. These findings stand to provide important guidance for understanding the deformation mechanisms of subgrade in warm permafrost regions, as well as for improving Qinghai-Tibet Railway embankment quality and operational safety.

DOI: 10.1016/j.enggeo.2019.105453

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