Permafrost Monthly Alerts (PMAs)

2022014061 Anonymous. Permafrost in a warming world: Nature Reviews. Earth & Environment, 3(1), January 2022. Individual papers within scope are cited separately.

2022014066 Angelopoulos, Michael (Alfred Wegener Institutute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany). Mapping subsea permafrost with electrical resistivity surveys: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), Article 6, January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00258-5

2022014068 Anisimov, Oleg (State Hydrological Institute, Department of Climatology, St. Petersburg, Russian Federation). Researching permafrost change requires all hands: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 8-9, January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00252-x

2022014067 Bouchard, Frédéric (Université Sherbrooke, Department of Applied Geometrics, Sherbrooke, QC, Canada); Fritz, Michael and Sjoberg, Ylva. Redrawing permafrost outreach: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), Article 7, January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00255-8

2022014073 Heijmans, Monique M. P. D. (Wageningen Univeristy and Research, Wageningen, Netherlands); Magnusson, Runa I.; Lara, Mark J.; Frost, Gerald V.; Myers-Smith, Isla H.; van Huissteden, Jacobus; Jorgenson, M. Torre; Fedorov, Alexander N.; Epstein, Howard E.; Lawrence, David M. and Limpens, Juul. Tundra vegetation change and impacts on permafrost: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 68-84, 182 ref., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00233-0

2022014065 Hille, Erika (Queen's University, Department of Geography and Planning, Kingston, ON, Canada). Using river geochemistry to monitor the hydrology of Arctic watersheds: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), Article 5, January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00257-6

2022014070 Hjort, Jan (University of Oulu, Geography Research Unit, Oulu, Finland); Streletskiy, Dmitry; Doré, Guy; Wu Qingbai; Bjella, Kevin L. and Luoto, Miska. Impacts of permafrost degradation on infrastructure: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 24-38, 167 ref., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00247-8

2022014071 Irrgang, Anna M. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Bendixen, Mette; Farquharson, Louise M.; Baranskaya, Alisa V.; Erikson, Li H.; Gibbs, Ann E.; Ogorodov, Stanislav A.; Overduin, Pier Paul; Lantuit, Hugues; Grigoriev, Mikhail N. and Jones, Benjamin M. Drivers, dynamics and impacts of changing Arctic coasts: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 39-54, 198 ref., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00232-1

2022014074 Jones, Benjamin M. (University of Alaska Fairbanks, Fairbanks, AK); Grosse, Guido; Farquharson, Louise M.; Roy-Léveillée, Pascale; Veremeeva, Alexandra; Kanevskiy, Mikhail Z.; Gaglioti, Benjamin V.; Breen, Amy L.; Parsekian, Andrew D.; Ulrich, Mathias and Hinkel, Kenneth M. Lake and drained lake basin systems in lowland permafrost regions: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 85-98, 200 ref., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00238-9

2022014064 Lou Peiqing (Chinese Academy of Sciences, Cryosphere Research Station on the Qinghai-Tibet Plateau, Lanzhou, China). Mapping permafrost thaw slumps with unmanned aerial vehicles: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), Article 4, illus., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00256-7

2022014072 Miner, Kimberley R. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA); Turetsky, Merritt R.; Malina, Edward; Bartsch, Annett; Tamminen, Johanna; McGuire, A. David; Fix, Andreas; Sweeney, Colm; Elder, Clayton D. and Miller, Charles E. Permafrost carbon emissions in a changing Arctic: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 55-67, 195 ref., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00230-3

2022014069 Smith, Sharon L. (Geological Survey of Canada, Ottawa, ON, Canada); O'Neill, H. Brendan; Isaksen, Ketil; Noetzli, Jeannette and Romanovsky, Vladimir E. The changing thermal state of permafrost: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), p. 10-23, 174 ref., January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00240-1

2022014062 Ulrich, Robert (University of California Los Angeles, Department of Earth, Planetary, and Space Sciences, Los Angeles, CA). Funding agricultural emission mitigation: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), Article 2, January 2022. Published Dec. 20, 2021; Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00260-x

2022014063 Wang Dong (Chinese Academy of Sciences, Cryosphere Research Station of the Qinghai-Tibet Plateau, Lanzhou, China). Digital soil mapping in Tibetan Plateau permafrost regions: in Permafrost in a warming world, Nature Reviews. Earth & Environment, 3(1), Article 3, January 2022. Based on Publisher-supplied data.

DOI: 10.1038/s43017-021-00254-9

2022014095 Bearzot, Francesca (University of Milano at Bicocca, Department of Earth and Environmental Sciences, Milan, Italy); Garzonio, Roberto; Di Mauro, Biagio; Colombo, Roberto; Cremonese, Edoardo; Crosta, Giovanni B.; Delaloye, Reynald; Hauck, Christian; Di Cella, Umberto Morra; Pogliotti, Paolo; Frattini, Paolo and Rossini, Micol. Kinematics of an alpine rock glacier from multi-temporal UAV surveys and GNSS data: Geomorphology, 402, Article 108116, April 2022. Based on Publisher-supplied data.

The quantification of rock glacier dynamics has gained increasing importance in recent years. In this study, the spatial and temporal flow patterns of perennially frozen debris in the active Gran Sometta rock glacier (Western Italian Alps) were investigated with repeated Unmanned Aerial Vehicle (UAV) surveys (2016-2019), Global Navigation Satellite System (GNSS) campaigns (2012-2020), geophysical prospections (2015) and ground surface temperature data (2014-2020). UAV data were used to generate maps of changes and elevation differences of the rock glacier surface by 3D point cloud comparison to evaluate surface lowering and accumulation processes. Horizontal velocities were quantified by an automatic image correlation technique and the results were then compared with horizontal surface velocities from GNSS measurements on selected points. The horizontal velocities estimated with the automatic method agree well with the GNSS velocities with an R²=0.99 and a RMSE lower than 0.07 m/y. Point cloud comparisons show surface lowering in the orographic left-hand side of the terminal part and in the central body of the rock glacier. The upper part exhibits almost absence of subsidence and any movement. This is explained by the lack of permafrost in this sector due to its overriding by the development of a small glacier during the Little Ice Age. As a result of the downslope movement, zones of surface rising occurred at the advancing front and at the moving ridge and furrow complexes. Surface velocity decreases from the orographic left to the right-hand side of the rock glacier tongue, where a thaw subsidence of up to 0.05 m/y was also observed. According to the GNSS measurements, the range of flow velocity of the rock glacier increased from 0.17-1.1 m/y in 2013 to 0.21-1.45 m/y in 2015 and then decreased until 2018 when the smallest surface velocity is detected. Since 2018, the creep velocities gradually started to increase again reaching values of 0.23 m/y up to a maximum of 1.9 m/y in the orographic left-hand side of the rock glacier tongue. This agrees with observations from other rock glaciers in the European Alps in recent decades. The complex Gran Sometta rock glacier dynamics can be explained by the heterogeneous distribution of permafrost and related subsurface perennially frozen ground which is thick enough (about 20-30 m) for permafrost creep to occur. Creep rates of the rock glacier permafrost depend also on the ground thermal regime: annual warmer surface conditions promote an acceleration of the creep rates within the rock glacier permafrost, whereas ground surface cooling causes a slight deceleration.

DOI: 10.1016/j.geomorph.2022.108116

2022013956 Han, Li (Heidelberg University, Department of Geography, Heidelberg, Germany) and Menzel, Lucas. Hydrological variability in southern Siberia and the role of permafrost degradation: Journal of Hydrology, 604, Article no. 127203, illus. incl. 1 table, sketch maps, 100 ref., January 2022.

Changes in the cryosphere caused by global warming are expected to alter the hydrological cycle, with consequences to freshwater availability for humans and ecosystems. Here, we combine data assimilation, cross-correlation analysis, simulation techniques, and the conceptual steady-state Budyko framework to examine the driving mechanisms of historical hydrological changes at annual, seasonal, and monthly scales. We focus on two southern Siberian basins with different landscape properties: the semi-arid Selenga, characterized by discontinuous, sporadic, and isolated permafrost; and the boreal Aldan, which is underlain by continuous permafrost. Our results indicate that the two basins show divergent trends in river runoff over the period 1954-2013. In Selenga, runoff exhibits a significant decreasing trend (-1.3 km³/10 yrs, p≤&eq;0.05), whereas a remarkable increasing trend (4.4 km³/10 yrs, p≤&eq;0.05) occurs in Aldan. Given the negligible trends in precipitation over both basins, we attribute these contrasting changes to different impacts from warming-induced permafrost degradation. The Selenga basin, which is dominated by lateral degradation (i.e., decreasing permafrost extent), suffers from severe water loss via the enhanced infiltration of water that was previously stored close to the surface. This leads to a water-deficit surface condition. In the Aldan basin, in contrast, vertical degradation prevails: the thickened active layer is still underlain by a frozen layer with low permeability that sustains water-rich surface conditions. Furthermore, summer runoff shows contrasting oscillations, with wet-dry-wet-dry and dry-wet-dry-wet state evolutions in the Selenga and Aldan basins, respectively. We attribute such variabilities to the "seesaw-like" oscillations in summer precipitation associated with the propagation of Rossby wave trains across the Eurasian continent. We also find that warming-induced permafrost degradation over the 30-year period from 1984 to 2013 has led to strong regime shifts in river runoff in both basins. Our study highlights the importance of examining the mechanisms that drive changes in water availability from an integrated land-hydrology-atmosphere system perspective.

DOI: 10.1016/j.jhydrol.2021.127203

2022014100 Buter, Anuschka (Free University of Bozen-Bolzano, Faculty of Science and Technology, Bolzano, Italy); Heckmann, Tobias; Filisetti, Lorenzo; Savi, Sara; Mao, Luca; Gems, Bernhard and Comiti, Francesco. Effects of catchment characteristics and hydro-meteorological scenarios on sediment connectivity in glacierised catchments: Geomorphology, 402, Article 108128, illus. incl. 2 tables, geol. sketch maps, 90 ref., April 2022.

In the past decade, sediment connectivity has become a widely recognized characteristic of a geomorphic system. However, the quantification of functional connectivity (i.e. connectivity which arises due to the actual occurrence of sediment transport processes) and its variation over space and time is still a challenge. In this context, this study assesses the effects of expected future phenomena in the context of climate change (i.e. glacier retreat, permafrost degradation or meteorological extreme events) on sediment transport dynamics in a glacierised Alpine basin. The study area is the Sulden river basin (drainage area 130 km²) in the Italian Alps, which is composed of two geomorphologically diverse sub-basins. Based on graph theory, we evaluated the spatio-temporal variations in functional connectivity in these two sub-basins. The graph-object, obtained by manually mapping sediment transport processes between landforms, was adapted to 6 different hydro-meteorological scenarios, which derive from combining base, heatwave and rainstorm conditions with snowmelt and glacier-melt periods. For each scenario and each sub-basin, the sediment transport network and related catchment characteristics were analysed. To compare the effects of the scenarios on functional connectivity, we introduced a connectivity degree, calculated based on the area of the landforms involved in sediment cascades. Results indicate that the area of the basin connected to its outlet in terms of sediment transport might feature a six-fold increase in case of rainstorm conditions compared to "average" meteorological conditions assumed for the base scenario. Furthermore, markedly different effects of climate change on sediment connectivity are expected between the two sub-catchments due to their contrasting morphological and lithological characteristics, in terms of relative importance of rainfall-triggered colluvial processes vs temperature-driven proglacial fluvial dynamics.

DOI: 10.1016/j.geomorph.2022.108128

2022014138 Paull, Charles K. (Monterey Bay Aquarium Research Institute, Science Division, Moss Landing, CA); Dallimore, Scott R.; Jin, Young Keun; Caress, David W.; Lundsten, Eve; Gwiazda, Roberto; Anderson, Krystle; Hughes Clarke, John; Youngblut, Scott and Melling, Humfrey. Rapid seafloor changes associated with the degradation of Arctic submarine permafrost: Proceedings of the National Academy of Sciences of the United States of America, 119(12), Article e2119105119, illus. incl. geol. sketch maps, 53 ref., March 22, 2022.

Repeated high-resolution bathymetric surveys of the shelf edge of the Canadian Beaufort Sea during 2- to 9-y-long survey intervals reveal rapid morphological changes. New steep-sided depressions up to 28 m in depth developed, and lateral retreat along scarp faces occurred at multiple sites. These morphological changes appeared between 120-m and 150-m water depth, near the maximum limit of the submerged glacial-age permafrost, and are attributed to permafrost thawing where ascending groundwater is concentrated along the relict permafrost boundary. The groundwater is produced by the regional thawing of the permafrost base due to the shift in the geothermal gradient as a result of the interglacial transgression of the shelf. In contrast, where groundwater discharge is reduced, sediments freeze at the ambient sea bottom temperature of ~-1.4°C. The consequent expansion of freezing sediment creates ice-cored topographic highs or pingos, which are particularly abundant adjacent to the discharge area.

DOI: 10.1073/pnas.2119105119

2022012825 Kunz, Julius (University of Würzburg, Institute of Geography and Geology, Wurzburg, Germany); Ullmann, Tobias and Kneisel, Christof. Internal structure and recent dynamics of a moraine complex in an alpine glacier forefield revealed by geophysical surveying and Sentinel-1 InSAR time series: Geomorphology, 398, Article 108052, illus. incl. 1 table, geol. sketch maps, 75 ref., February 1, 2022.

This study presents results on the internal structure and recent dynamics of a thrust moraine complex in the Zay Valley (Italian Alps) by means of geophysical surveying and remote sensing time series. Results from electrical resistivity tomography, seismic refraction tomography, ground-penetrating radar as well as a four-phase modeling approach provided detailed information on the internal moraine structure and confirmed the presence of partly ice-rich permafrost within the moraine complex as well as buried massive ice of sedimentary origin within the proximal moraine flank. The use of Synthetic Aperture Radar interferometry (InSAR) enabled the derivation of detailed surface displacement patterns showing subsidence rates of up to 5 cm within a 30-day period (August/September 2020) over the central part of the moraine complex. Further, preliminary InSAR results indicated an eastward displacement back towards the glacier forefield. The comparison of the results from geophysical measurements and InSAR time series suggested a strong relationship between the subsurface conditions and the surface displacement, as highest displacement rates were found over locations with highest ice content. The consistency of the results enables an area wide estimation of subsurface conditions and highlights the benefits from combining geophysical and remote sensing methods.

DOI: 10.1016/j.geomorph.2021.108052

2022011406 Liu Shibo (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Cryospheric Science, Cryosphere Research Station on the Qinghai-Tibet Plateau, Lanzhou, China); Zhao Lin; Wang Lingxiao; Zhou Huayun; Zou Defu; Sun Zhe; Xie Changwei and Qiao Yongping. Intra-annual ground surface deformation detected by site observation, simulation and InSAR monitoring in permafrost site of Xidatan, Qinghai-Tibet Plateau: Geophysical Research Letters, 49(3), Article e2021GL095029, illus., 37 ref., February 16, 2022.

The permafrost degradation can cause long-term ground surface subsidence, and the surface undergoes frost heave and thaw settlement due to the ice-water phase change in the active layer. The multi-year surveys by leveling observations and Interferometric Synthetic Aperture Radar monitoring (InSAR) are helpful to understand the characteristics of seasonal deformation and to model the permafrost terrain surface deformation. In this paper, we studied the characteristics of seasonal deformation over permafrost terrain in Xidatan, obtained by leveling measurements from 2010 to 2018, Sentinel-1 data from 2014 to 2020, and hydrothermal-data-based simulation. The results consistently showed a four-stage pattern of seasonal deformation characteristics: Summer thaw subsiding, warm-season stable-standing, winter freeze heaving and stable-standing. The leveling measurements proved that spatial heterogeneity also exists on a small spatial scale (400 m²). The deformation amplitude obtained by leveling data is the largest, and the InSAR data is the smallest. Abstract Copyright (2022). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GL095029

2022014023 Zhong Wen (Wuhan University, School of Geodesy and Geomatics, Wuhan, China); Yuan Qiangqiang; Liu Tingting and Yue Linwei. Freeze/thaw onset detection combining SMAP and ASCAT data over Alaska; a machine learning approach: Journal of Hydrology, 605, Article no. 127354, illus. incl. 1 table, sketch maps, 60 ref., February 2022.

In the context of global warming, permafrost degrades gradually. To cope with the instability of the cryosphere, it is very important to strengthen the monitoring of the seasonal freeze-thaw cycle. At present, active and passive microwave remote sensing data are widely used in freeze/thaw (F/T) onset detection. There is some potential to improve accuracy through the combination of active and passive microwave data. Compared with the traditional method for combination, the machine learning algorithm has a stronger nonlinear expression ability. Therefore, it is advisable to use machine learning to combine multi-source data for freeze/thaw onset detection. In this study, the temporal change detection method is applied to SMAP data and ASCAT data respectively for preliminary detection. Then the Random Forest algorithm (RF) is used to combine the preliminary results of active and passive microwave data with site observation to estimate the freeze/thaw onsets more accurately. The method is validated with data obtained in Alaska from 2015 to 2019. The accuracy evaluation shows that the proposed method can effectively improve the accuracy of freeze/thaw onset detection. The predicted distribution of the freeze/thaw cycle indicates that the variation of the freeze-thaw cycle is closely related to latitude. In general, the proposed method based on machine learning is promising in the research of freeze-thaw state monitoring.

DOI: 10.1016/j.jhydrol.2021.127354

2022011381 Holmes, M. Elizabeth (Florida State University, Department of Earth, Ocean, and Atmospheric Science, Tallahassee, FL); Crill, Patrick M.; Burnett, William C.; McCalley, Carmody K.; Wilson, Rachel M.; Frolking, S.; Chang, Kuang-Yu; Riley, William J.; Varner, Ruth K.; Hodgkins, Susanne B.; McNichol, A. P.; Saleska, S. R.; Rich, Virginia I.; Chanton, Jeffrey P.; and . Carbon accumulation, flux, and fate in Stordalen Mire, a permafrost peatland in transition: Global Biogeochemical Cycles, 36(1), Article e2021GB007113, illus. incl. 3 tables, sketch map, 99 ref., January 2022.

Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum-dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi-decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi-continuous measurement of CO₂ and CH₄ exchange, and 21 core profiles for ²¹⁰Pb and ¹⁴C peat dating. Year-round chamber measurements indicated net carbon balance of -13±8, -49±15, and -91±43 g C m^-2 y^-1 for the years 2012-2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO₂ uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO₂ fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial-scale levels (17-29 g C m^-2 y^-1) to moderate aCAR of the past century (72-81 g C m^-2 y^-1) to higher recent aCAR of 90-147 g C m^-2 y^-1. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO₂ sink, but this CO₂ sink is increasingly offset by rising CH₄ emissions, dominated by modern carbon as determined by ¹⁴C. The higher CH₄ emissions result in higher net CO_2-equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate. Abstract Copyright (2022), American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GB007113

2022011228 Kim, Kwansoo (Korea Polar Research Institute, Incheon, South Korea); Lee, Joohan; Ju, Hyeontae; Jung, Ji Young; Chae, Namyi; Chi, Junhwa; Kwon, Min Jung; Lee, Bang Yong; Wagner, Johann and Kim, Ji-Soo. Time-lapse electrical resistivity tomography and ground penetrating radar mapping of the active layer of permafrost across a snow fence in Cambridge Bay, Nunavut Territory, Canada; correlation interpretation using vegetation and meteorological data: Geosciences Journal (Seoul), 25(6), p. 877-890, illus. incl. geol. sketch map, 30 ref., December 2021.

The active layer thickness (ALT) is a key parameter for permafrost studies. Changes in the ALT are affected mainly by air and ground temperatures, physical and thermal properties of the surface and subsurface materials, soil moisture, vegetation, and the duration and thickness of snow cover. Ground penetrating radar (GPR) and electrical resistivity tomography (ERT) were employed across a snow fence during the thawing season to delineate and monitor the active layer of permafrost in Cambridge Bay, Nunavut, Canada. The variation of the ALT is well captured by the high-resolution time-lapse radargram. At the position of the fence, the active layer thickens over the thawing period from 0.5 m depth at the beginning to 1.0 m depth at the end. The active layer is thicker in the pre-fence area (C zone) than in the post-fence area (H zone). As the air temperature increases with time, the difference in thickness between the two zones decreases, eventually becoming almost equal. Changes in the ALT are represented in the ERT by low resistivities (< 200 Wm), which decrease gradually with time. This occurs most significantly in the H zone due to the rapidly increasing temperature in the absence of snow cover. The electrical resistivity structure of the active layer is well correlated with the vegetation activity, as measured by the normalized difference vegetation index, air/ground temperatures, soil moisture, snow cover, and snow accumulation controlled by the fence. Geophysical data interpretation and correlation schemes with vegetation and meteorological data explored in this paper can be applied to monitor the active layer, which is expected to thin during the freezing season.

DOI: 10.1007/s12303-021-0021-7

2022011326 Park, Hotaek (Japan Agency for Marine-Earth Science and Technology, Institute of Arctic Climate and Environment Research, Yokosuka, Japan); Tanoue, Masahiro; Sugimoto, Atsuko; Ichiyanagi, Kimpei; Iwahana, Go and Hiyama, Tetsuya. Quantitative separation of precipitation and permafrost waters used for evapotranspiration in a Boreal forest; a numerical study using tracer model: Journal of Geophysical Research: Biogeosciences, 126(12), Article e2021JG006645, illus. incl. 1 table, 65 ref., December 2021.

Arctic precipitation (P_G) that occurs as rainfall (P_rain) or snowfall (P_snow) depending on the prevailing climatic conditions results in seasonally specific hydrological events. Climate change can affect the P_G- and permafrost-originated water (P_ice) regimes, resulting in change to ecohydrological processes. However, the relative influences of source waters (i.e., P_rain, P_snow, and P_ice) on terrestrial hydrological processes have not yet been fully established. Here, we report the development and implementation of a numerical water tracer model designed to quantify changes in the storages and fluxes of the source waters and the hydrogen and oxygen isotopic tracers associated with hydrometeorological events. The presented tracer model was used to illustrate the spatiotemporal variability of the tracers in the surface-subsurface system of a deciduous needleleaf boreal forest and to separate the contribution rates of the tracer waters to evapotranspiration (ET). Although P_snow accounted for 22%-57% of ET and the subcomponents, the contribution rates to soil evaporation and transpiration were significant only during spring. The major source water for soil moisture was P_rain, which accounted for 69.2% of ET and showed an increasing trend during 1980-2016. Additionally, P_rain also accounted for 77.2% of transpiration. Under the present conditions of warming permafrost, P_ice demonstrated negligibly low impact on ET. The tracer model was shown capable of quantifying the contribution rates of tracer waters to ET, highlighting the advantages of the tracer model for a similar quantitative separation regarding future climate change. Abstract Copyright (2021), The Authors.

DOI: 10.1029/2021JG006645

2022013913 Li Yuheng (China Three Gorges Corporation, Beijing, China); Wang Taihua; Yang Dawen; Tang Lihua; Yang Kun and Liu Zhiwu. Linkage between anomalies of pre-summer thawing of frozen soil over the Tibetan Plateau and summer precipitation in East Asia: Environmental Research Letters, 16(11), Paper no. 114030, illus. incl. sketch maps, 53 ref., November 2021.

The Tibetan Plateau (TP) is sensitive to climate change in the land-atmosphere coupling mechanism due to its complex topographic features and unique geographic location. This study explored the teleconnection between pre-summer thawing of frozen soil over the TP and summer precipitation in East Asia in the Meiyu-Baiu rainy season (June, July) from 1981 to 2019 using maximum covariance analysis (MCA). The precipitation fields forced by thawing of frozen soil were calculated by the coupled manifold technique. The variations in East Asian precipitation are significantly impacted by thawing of frozen soil over the TP, with a variance explained ratio in the surrounding middle and lower reaches of Yangtze River (MLYR) of around 10%-20%. The MCA analysis also revealed that the thickness of pre-summer frozen soil thawing had a positive relationship with summer precipitation in the MLYR and southern Japan (fraction=0.59, correlation ~0.99). To find out the possible mechanism, composite analyses were conducted on atmospheric and surface components with reanalysis products. The analysis results suggested that more (less) frozen soil thawing would increase (decrease) the sensible heat and land surface temperature with enhanced (weakened) surface diabatic heating over the TP. Then, the positive (negative) surface diabatic heating would result in an enhanced (weakened) South Asia High extending eastward followed by stronger (weaker) upper troposphere (200 hPa) westerlies, as well as the West North Pacific Subtropical High extending westward. As a result, the northeastward movement of the integrated vapor transport intensified (weakened) with the westward extension (eastward retreat) of the Meiyu-Baiu rain belt, leading to more (less) precipitation in the MLYR and southern Japan. It is thus suggested that pre-summer thawing of frozen soil over the TP could play a vital role in regulating East Asian summer precipitation and movement of the Meiyu-Baiu rain belt. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/ac2f1c

2022013901 Grebenets, Valery I. (Moscow State University, Department of Cryolithology and Glaciology, Moscow, Russian Federation); Tolmanov, Vasily A.; Iurov, Fedor D. and Groisman, Pavel Y. The problem of storage of solid waste in permafrost: Environmental Research Letters, 16(10), Paper no. 105007, illus., 35 ref., October 2021. Part of a special issue entitled Focus on northern Eurasia in the global Earth and human systems, changes, interactions, and sustainable societal development, edited by Groisman, P. et al.

The specifics of solid waste storage in permafrost were analyzed. The main types of impact of the waste on the natural environment and frozen soils were determined as mechanical, physicochemical, load, and thermal. The research allowed us to define eight main types of waste storage in the permafrost zone, which were different both in terms of waste accumulation and in terms of their impact on the environment in general and the permafrost in particular. These were: industrial waste storage facilities (slag, sludge and tailing dumps, ash dumps); dumps of rock in sites of mining; household waste accumulators; dumps of wood processing waste in the centers of the timber industry; abandoned territories resulting from a decrease in the population of Northern settlements; storage areas for tanks with residues of fuels and lubricants; tank farms for storing petroleum products in settlements and cities of the North; storage areas for contaminated snow exported from built-up areas. Pollution of waste territories and destruction of many ecosystems as a result of waste storage were caused by use of imperfect technologies for the extraction and processing of raw materials, the 'legacy' of past years with disregard to the environmental conditions, the lack of special standards for the storage of garbage and by-product industrial materials, undeveloped methods of waste disposal in harsh climatic conditions. Copyright (Copyright) 2021 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/ac2375

2022011161 Golubev, V. N. (Russian Academy of Sciences, Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Moscow, Russian Federation); Tarasov, N. N.; Chernyshev, I. V.; Chugaev, A. V.; Ochirova, G. V. and Kochkin, B. T. Post-ore processes of uranium migration in the sandstone hosted type deposits; ²³⁴U/²³⁸U, ²³⁸U/²³⁵U and U-Pb systematics of ores of the Namaru Deposit, Vitim District, northern Transbaikalia: Geology of Ore Deposits, 63(4), p. 287-299, illus. incl. 3 tables, sect., 24 ref., July 2021.

To assess the nature of the post-ore behaviour of uranium in the Namaru deposit (Khiagda ore field), U-Pb isotope systems and the isotopic composition of uranium (²³⁴U/²³⁸U and ²³⁸U/²³⁵U) were studied. The studied samples represent different ore zones of the deposit and were collected along cross-sections both vertically and horizontally. Wide variations in the isotopic composition of uranium and U-Pb isotopic age have been established. Deviations of the ²³⁴U/²³⁸U ratio from equilibrium values, which for some samples exceed 50%, along with significant variations in the isotopic age, indicate that permafrost layer, which covered the catchment areas of paleovalleys with meteoric oxygen-containing waters ca. 2.5 Ma ago, did not lead to preserving uranium ores at the deposit. Uranium migration took place during the Quaternary period. The effective combining the U-Pb dating and ²³⁴U/²³⁸U data in assessing the post-ore redistribution of uranium made it possible to recognize: removal of uranium from some zones of the ore body and its accompanying redeposition in others. Wide variations in the ²³⁸U/²³⁵U (137.484-137.851) ratios throughout the entire studied cross-sections can be explained by the different locations of samples relatively to the ore deposition front and change in redox conditions as this front advanced. Depletion of the light isotope ²³⁵U in the lower zone of the ore body may be associated with the influence of ascending carbonic waters established in the regional basement. The effect of such waters on uranium-bearing rocks causes predominant leaching of light ²³⁵U.

DOI: 10.1134/S1075701521040024

2022010590 Mueller, Carsten W. (Technical University of Munich, Research Department Ecology and Ecosystem Management, Freising-Weihenstephan, Germany); Steffens, Markus and Buddenbaum, Henning. Permafrost soil complexity evaluated by laboratory imaging vis-NIR spectroscopy: European Journal of Soil Science, 72(1), p. 114-119, illus. incl. 1 table, 30 ref., January 2021.

The biogeochemical functioning of soils (e.g., soil carbon stabilization and nutrient cycling) is determined at the interfaces of specific soil structures (e.g., aggregates, particulate organic matter (POM) and organo-mineral associations). With the growing accessibility of spectromicroscopic techniques, there is an increase in nano- to microscale analyses of biogeochemical interfaces at the process scale, reaching from the distribution of elements and isotopes to the localization of microorganisms. A widely used approach to study intact soil structures is the fixation and embedding of intact soil samples in resin and the subsequent analyses of soil cross-sections using spectromicroscopic techniques. However, it is still challenging to link such microscale approaches to larger scales at which normally bulk soil analyses are conducted. Here we report on the use of laboratory imaging Vis-NIR spectroscopy on resin embedded soil sections and a procedure for supervised image classification to determine the microscale soil structure arrangement, including the quantification of soil organic matter fractions. This approach will help to upscale from microscale spectromicroscopic techniques to the centimetre and possibly pedon scale. Thus, we demonstrate a new approach to integrate microscale soil analyses into pedon-scale conceptual and experimental approaches.

DOI: 10.1111/ejss.12927

2022013875 Douglas, Thomas A. (U. S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK); Hiemstra, Christopher A.; Anderson, John E.; Barbato, Robyn A.; Bjella, Kevin L.; Deeb, Elias J.; Gelvin, Arthur B.; Nelsen, Patricia E.; Newman, Stephen D.; Saari, Stephanie P. and Wagner, Anna M. Recent degradation of interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne lidar: The Cryosphere (Online), 15(8), p. 3555-3575, illus. incl. 2 tables, sketch map, 84 ref., 2021.

Permafrost underlies one-quarter of the Northern Hemisphere but is at increasing risk of thaw from climate warming. Recent studies across the Arctic have identified areas of rapid permafrost degradation from both top-down and lateral thaw. Of particular concern is thawing syngenetic "yedoma" permafrost which is ice-rich and has a high carbon content. This type of permafrost is common in the region around Fairbanks, Alaska, and across central Alaska expanding westward to the Seward Peninsula. A major knowledge gap is relating belowground measurements of seasonal thaw, permafrost characteristics, and residual thaw layer development with aboveground ecotype properties and thermokarst expansion that can readily quantify vegetation cover and track surface elevation changes over time. This study was conducted from 2013 to 2020 along four 400 to 500 m long transects near Fairbanks, Alaska. Repeat active layer depths, near-surface permafrost temperature measurements, electrical resistivity tomography (ERT), deep (>5 m) boreholes, and repeat airborne light detection and ranging (lidar) were used to measure top-down permafrost thaw and map thermokarst development at the sites. Our study confirms previous work using ERT to map surface thawed zones; however, our deep boreholes confirm the boundaries between frozen and thawed zones that are needed to model top-down, lateral, and bottom-up thaw. At disturbed sites seasonal thaw increased up to 25% between mid-August and early October and suggests measurements to evaluate active layer depth must be made as late in the fall season as possible because the projected increase in the summer season of just a few weeks could lead to significant additional thaw. At our sites, tussock tundra and spruce forest are associated with the lowest mean annual near-surface permafrost temperatures while mixed-forest ecotypes are the warmest and exhibit the highest degree of recent temperature warming and thaw degradation. Thermokarst features, residual thaw layers, and taliks have been identified at all sites. Our measurements, when combined with longer-term records from yedoma across the 500 000 km² area of central Alaska, show widespread near-surface permafrost thaw since 2010. Projecting our thaw depth increases, by ecotype, across the yedoma domain, we calculate a first-order estimate that 0.44 Pg of organic carbon in permafrost soil has thawed over the past 7 years, which, for perspective, is an amount of carbon nearly equal to the yearly CO₂ emissions of Australia. Since the yedoma permafrost and the variety of ecotypes at our sites represent much of the Arctic and subarctic land cover, this study shows remote sensing measurements, top-down and bottom-up thermal modeling, and ground-based surveys can be used predictively to identify areas of the highest risk for permafrost thaw from projected future climate warming.

DOI: 10.5194/tc-15-3555-2021

2022013889 Fischer, Melanie (University of Potsdam, Institute of Environmental Science and Geography, Potsdam, Germany); Korup, Oliver; Veh, Georg and Walz, Ariane. Controls of outbursts of moraine-dammed lakes in the greater Himalayan region: The Cryosphere (Online), 15(8), p. 4145-4163, illus. incl. 5 tables, sketch map, 91 ref., 2021.

Glacial lakes in the Hindu Kush-Karakoram-Himalayas-Nyainqentanglha (HKKHN) region have grown rapidly in number and area in past decades, and some dozens have drained in catastrophic glacial lake outburst floods (GLOFs). Estimating regional susceptibility of glacial lakes has largely relied on qualitative assessments by experts, thus motivating a more systematic and quantitative appraisal. Before the backdrop of current climate-change projections and the potential of elevation-dependent warming, an objective and regionally consistent assessment is urgently needed. We use an inventory of 3390 moraine-dammed lakes and their documented outburst history in the past four decades to test whether elevation, lake area and its rate of change, glacier-mass balance, and monsoonality are useful inputs to a probabilistic classification model. We implement these candidate predictors in four Bayesian multi-level logistic regression models to estimate the posterior susceptibility to GLOFs. We find that mostly larger lakes have been more prone to GLOFs in the past four decades regardless of the elevation band in which they occurred. We also find that including the regional average glacier-mass balance improves the model classification. In contrast, changes in lake area and monsoonality play ambiguous roles. Our study provides first quantitative evidence that GLOF susceptibility in the HKKHN scales with lake area, though less so with its dynamics. Our probabilistic prognoses offer improvement compared to a random classification based on average GLOF frequency. Yet they also reveal some major uncertainties that have remained largely unquantified previously and that challenge the applicability of single models. Ensembles of multiple models could be a viable alternative for more accurately classifying the susceptibility of moraine-dammed lakes to GLOFs.

DOI: 10.5194/tc-15-4145-2021

2022013951 Gibbs, Ann E. (U. S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA); Erikson, Li H.; Jones, Benjamin M.; Richmond, Bruce M. and Engelstad, Anita C. Seven decades of coastal change at Barter Island, Alaska; exploring the importance of waves and temperature on erosion of coastal permafrost bluffs: Remote Sensing, 13(21), Article 4420, illus. incl. 2 tables, sketch maps, 47 ref., 2021. Part of a special issue entitled Multi-scale analysis for detecting the processes, causes, and impacts of permafrost change and of disruptive events, edited by Lim, M., Vieira, G., and Whalen, D.

Observational data of coastal change over much of the Arctic are limited largely due to its immensity, remoteness, harsh environment, and restricted periods of sunlight and ice-free conditions. Barter Island, Alaska, is one of the few locations where an extensive, observational dataset exists, which enables a detailed assessment of the trends and patterns of coastal change over decadal to annual time scales. Coastal bluff and shoreline positions were delineated from maps, aerial photographs, and satellite imagery acquired between 1947 and 2020, and at a nearly annual rate since 2004. Rates and patterns of shoreline and bluff change varied widely over the observational period. Shorelines showed a consistent trend of southerly erosion and westerly extension of the western termini of Barter Island and Bernard Spit, which has accelerated since at least 2000. The 3.2 km long stretch of ocean-exposed coastal permafrost bluffs retreated on average 114 m and at a maximum of 163 m at an average long-term rate (70 year) of 1.6±0.1 m/yr. The long-term retreat rate was punctuated by individual years with retreat rates up to four times higher (6.6±1.9 m/yr; 2012-2013) and both long-term (multidecadal) and short-term (annual to semiannual) rates showed a steady increase in retreat rates through time, with consistently high rates since 2015. A best-fit polynomial trend indicated acceleration in retreat rates that was independent of the large spatial and temporal variations observed on an annual basis. Rates and patterns of bluff retreat were correlated to incident wave energy and air and water temperatures. Wave energy was found to be the dominant driver of bluff retreat, followed by sea surface temperatures and warming air temperatures that are considered proxies for evaluating thermo-erosion and denudation. Normalized anomalies of cumulative wave energy, duration of open water, and air and sea temperature showed at least three distinct phases since 1979: a negative phase prior to 1987, a mixed phase between 1987 and the early to late 2000s, followed by a positive phase extending to 2020. The duration of the open-water season has tripled since 1979, increasing from approximately 40 to 140 days. Acceleration in retreat rates at Barter Island may be related to increases in both thermodenudation, associated with increasing air temperature, and the number of niche-forming and block-collapsing episodes associated with higher air and water temperature, more frequent storms, and longer ice-free conditions in the Beaufort Sea.

DOI: 10.3390/rs13214420

2022013885 Harp, Dylan R. (Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM); Zlotnik, Vitaly; Abolt, Charles J.; Busey, Bob; Avendaño, Sofia T.; Newman, Brent D.; Atchley, Adam L.; Jafarov, Elchin; Wilson, Cathy J. and Bennett, Katrina E. New insights into the drainage of inundated ice-wedge polygons using fundamental hydrologic principles: The Cryosphere (Online), 15(8), p. 4005-4029, illus. incl. 1 table, sketch map, 78 ref., 2021. Includes appendix.

The pathways and timing of drainage from the inundated centers of ice-wedge polygons in a warming climate have important implications for carbon flushing, advective heat transport, and transitions from methane to carbon dioxide dominated emissions. Here, we expand on previous research using a recently developed analytical model of drainage from a low-centered polygon. Specifically, we perform (1) a calibration to field data identifying necessary model refinements and (2) a rigorous model sensitivity analysis that expands on previously published indications of polygon drainage characteristics. This research provides intuition on inundated polygon drainage by presenting the first in-depth analysis of drainage within a polygon based on hydrogeological first principles. We verify a recently developed analytical solution of polygon drainage through a calibration to a season of field measurements. Due to the parsimony of the model, providing the potential that it could fail, we identify the minimum necessary refinements that allow the model to match water levels measured in a low-centered polygon. We find that (1) the measured precipitation must be increased by a factor of around 2.2, and (2) the vertical soil hydraulic conductivity must decrease with increasing thaw depth. Model refinement (1) accounts for runoff from rims into the ice-wedge polygon pond during precipitation events and possible rain gauge undercatch, while refinement (2) accounts for the decreasing permeability of deeper soil layers. The calibration to field measurements supports the validity of the model, indicating that it is able to represent ice-wedge polygon drainage dynamics. We then use the analytical solution in non-dimensional form to provide a baseline for the effects of polygon aspect ratios (radius to thaw depth) and coefficient of hydraulic conductivity anisotropy (horizontal to vertical hydraulic conductivity) on drainage pathways and temporal depletion of ponded water from inundated ice-wedge polygon centers. By varying the polygon aspect ratio, we evaluate the relative effect of polygon size (width), inter-annual increases in active-layer thickness, and seasonal increases in thaw depth on drainage. The results of our sensitivity analysis rigorously confirm a previous analysis indicating that most drainage through the active layer occurs along an annular region of the polygon center near the rims. This has important implications for transport of nutrients (such as dissolved organic carbon) and advection of heat towards ice-wedge tops. We also provide a comprehensive investigation of the effect of polygon aspect ratio and anisotropy on drainage timing and patterns, expanding on previously published research. Our results indicate that polygons with large aspect ratios and high anisotropy will have the most distributed drainage, while polygons with large aspect ratios and low anisotropy will have their drainage most focused near their periphery and will drain most slowly. Polygons with small aspect ratios and high anisotropy will drain most quickly. These results, based on parametric investigation of idealized scenarios, provide a baseline for further research considering the geometric and hydraulic complexities of ice-wedge polygons.

DOI: 10.5194/tc-15-4005-2021

2022013930 Khan, M. Ataullah Raza (Indian Institute of Remote Sensing, Geosciences Department, Dehradun, India); Singh, Shaktiman; Pandey, Pratima; Bhardwaj, Anshuman; Ali, Sheikh; Chaturvedi, Vasudha and Ray, Prashant. Modelling permafrost distribution in western Himalaya using remote sensing and field observations: Remote Sensing, 13(21), Article 4403, illus. incl. 4 tables, sketch maps, 122 ref., 2021. Part of a special issue entitled Applications of MODIS data for environmental research, edited by Singh, S., Bhardwaj, A., and Sam, L.

The presence and extent of permafrost in the Himalaya, which is a vital component of the cryosphere, remains severely under-researched with its future climatic-driven trajectory only partly understood and the future consequences on high-altitude ecosystem tentatively sketched out. Previous studies and available permafrost maps for the Himalaya relied primarily upon the modelled meteorological inputs to further model the likelihood of permafrost. Here, as a maiden attempt, we have quantified the distribution of permafrost at 30 m grid-resolution in the Western Himalaya using observations from multisource satellite datasets for estimating input parameters, namely temperature, potential incoming solar radiation (PISR), slope, aspect and land use, and cover. The results have been compared to previous studies and have been validated through field investigations and geomorphological proxies associated with permafrost presence. A large part of the study area is barren land (~69%) due to its extremely resistive climate condition with ~62% of the total area having a mean annual air temperature of (MAAT) <1°C. There is a high inter-annual variability indicated by varying standard deviation (1-3°C) associated with MAAT with low standard deviation in southern part of the study area indicating low variations in areas with high temperatures and vice-versa. The majority of the study area is northerly (~36%) and southerly (~38%) oriented, receiving PISR between 1 and 2.5 MW/m². The analysis of permafrost distribution using biennial mean air temperature (BMAT) for 2002-04 to 2018-20 suggests that the ~25% of the total study area has continuous permafrost, ~35% has discontinuous permafrost, ~1.5% has sporadic permafrost, and ~39% has no permafrost presence. The temporal analysis of permafrost distribution indicates a significant decrease in the permafrost cover in general and discontinuous permafrost in particular, from 2002-04 to 2018-20, with a loss of around 3% for the total area (~8340.48 km²). The present study will serve as an analogue for future permafrost studies to help understand the permafrost dynamics associated with the effects of the recent abrupt rise in temperature and change in precipitation pattern in the region.

DOI: 10.3390/rs13214403

2022013876 Myers, Krista F. (Louisiana State University, Department of Geology and Geophysics, Baton Rouge, LA); Doran, Peter T.; Tulaczyk, Slawek M.; Foley, Neil T.; Bording, Thue S.; Auken, Esben; Dugan, Hilary A.; Mikucki, Jill A.; Foged, Nikolaj; Grombacher, Denys and Virginia, Ross A. Thermal legacy of a large paleolake in Taylor Valley, East Antarctica, as evidenced by an airborne electromagnetic survey: The Cryosphere (Online), 15(8), p. 3577-3593, illus. incl. 1 table, sketch map, 55 ref., 2021.

Previous studies of the lakes of the McMurdo Dry Valleys have attempted to constrain lake level history, and results suggest the lakes have undergone hundreds of meters of lake level change within the last 20 000 years. Past studies have utilized the interpretation of geologic deposits, lake chemistry, and ice sheet history to deduce lake level history; however a substantial amount of disagreement remains between the findings, indicating a need for further investigation using new techniques. This study utilizes a regional airborne resistivity survey to provide novel insight into the paleohydrology of the region. Mean resistivity maps revealed an extensive brine beneath the Lake Fryxell basin, which is interpreted as a legacy groundwater signal from higher lake levels in the past. Resistivity data suggest that active permafrost formation has been ongoing since the onset of lake drainage and that as recently as 1500-4000 years BP, lake levels were over 60 m higher than present. This coincides with a warmer-than-modern paleoclimate throughout the Holocene inferred by the nearby Taylor Dome ice core record. Our results indicate Mid to Late Holocene lake level high stands, which runs counter to previous research finding a colder and drier era with little hydrologic activity throughout the last 5000 years.

DOI: 10.5194/tc-15-3577-2021

2022013936 Suzuki, Kazuyoshi (Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan); Park, Hotaek; Makarieva, Olga; Kanamori, Hironari; Hori, Masahiro; Matsuo, Koji; Matsumura, Shinji; Nesterova, Nataliia and Hiyama, Tetsuya. Effect of permafrost thawing on discharge of the Kolyma River, northeastern Siberia: Remote Sensing, 13(21), Article 4389, illus. incl. 2 tables, sketch maps, 58 ref., 2021. Part of a special issue entitled Remote sensing of water cycle science in the cryosphere, edited by Suzuki, K., Fassnacht, S., and Moreno, J.

With permafrost warming, the observed discharge of the Kolyma River in northeastern Siberia decreased between 1930s and 2000; however, the underlying mechanism is not well understood. To understand the hydrological changes in the Kolyma River, it is important to analyze the long-term hydrometeorological features, along with the changes in the active layer thickness. A coupled hydrological and biogeochemical model was used to analyze the hydrological changes due to permafrost warming during 1979-2012, and the simulated results were validated with satellite-based products and in situ observational records. The increase in the active layer thickness by permafrost warming suppressed the summer discharge contrary to the increased summer precipitation. This suggests that the increased terrestrial water storage anomaly (TWSA) contributed to increased evapotranspiration, which likely reduced soil water stress to plants. As soil freeze-thaw processes in permafrost areas serve as factors of climate memory, we identified a two-year lag between precipitation and evapotranspiration via TWSA. The present results will expand our understanding of future Arctic changes and can be applied to Arctic adaptation measures.

DOI: 10.3390/rs13214389

2022009487 Wang Chong (Nanjing University of Information Science & Technology, Key Laboratory of Meteorological Disaster of Ministry of Education, Joint International Research Laboratory of Climate and Environment Change, Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing, China); Zhao Lin; Fang Hongbing; Wang Lingxiao; Xing Zanpin; Zou Defu; Hu Guojie; Wu Xiaodong; Zhao Yonghua; Sheng Yu; Pang Qiangqiang; Du Erji; Liu Guangyue and Yun Hanbo. Mapping surficial soil particle size fractions in alpine permafrost regions of the Qinghai-Tibet Plateau: Remote Sensing, 13(7), Article 1392, illus. incl. 5 tables, geol. sketch maps, 78 ref., 2021.

Spatial information of particle size fractions (PSFs) is primary for understanding the thermal state of permafrost in the Qinghai-Tibet Plateau (QTP) in response to climate change. However, the limitation of field observations and the tremendous spatial heterogeneity hamper the digital mapping of PSF. This study integrated log-ratio transformation approaches, variable searching methods, and machine learning techniques to map the surficial soil PSF distribution of two typical permafrost regions. Results showed that the Boruta technique identified different covariates but retained those covariates of vegetation and land surface temperature in both regions. Variable selection techniques effectively decreased the data redundancy and improved model performance. In addition, the spatial distribution of soil PSFs generated by four log-ratio models presented similar patterns. Isometric log-ratio random forest (ILR-RF) outperformed the other models in both regions (i.e., R² ranged between 0.36 to 0.56, RMSE ranged between 0.02 and 0.10). Compared with three legacy datasets, our prediction better captured the spatial pattern of PSFs with higher accuracy. Although this study largely improved the accuracy of spatial distribution of soil PSFs, further endeavors should also be made to improve model accuracy and interpretability for a better understanding of the interaction and processes between environmental predictors and soil PSFs at permafrost regions.

DOI: 10.3390/rs13071392

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