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2022024921 Garankina, Ekaterina V. (Russian Academy of Sciences, Institute of Geography, Moscow, Russian Federation); Lobkov, Vasily A.; Shorkunov, Ilya G. and Belyaev, Vladimir R. Identifying relict periglacial features in watershed landscape and deposits of Borisoglebsk Upland, Central European Russia: Journal of the Geological Society of London, Pre-Issue Publication, illus. incl. 3 tables, sects., 101 ref., April 13, 2022.
Watershed landscapes of the Central Russian Plain being subject of the Late Pleistocene permafrost bear witness to widespread cryogenic structuring. It is reflected both in semi-regular spots, blocks, and polygons in soil and vegetation cover on arable fields and as vertically-orientated wedge casts in surficial deposits. The research aimed at identifying relict periglacial features both in landscape and sedimentary sequence of the Borisoglebsk Upland to determine if there is a correspondence of those cast networks to the distribution of landforms and regular patterns of soil and vegetation cover. Combined interpretation of aerial and satellite multi-temporal imagery and detailed investigation of vertical cross-sections in gradually expanding geotechnical trenches including apparent magnetic susceptibility measurements allowed to reveal and spatially correlate three generations of wedge casts, each buried by well-pronounced sedimentary units, and a specific bulbous kind of casts. Type of cryogenesis, erosion, and slope mass-movements shifted from the Late Pleniglacial to Late Glacial, representing a good proxy in the watershed sedimentary cover for palaeoenvironmental reconstructions. However, regular polygonal patterns caused by those casts are almost erased in the modern topography while shallow dry gullies mostly inherit pre-Holocene wider linear depressions with no clear respect to the buried cryogenic polygons.
DOI: 10.1144/jgs2021-135
2022021781 Gao Weifeng (Beijing University of Civil Engineering and Architecture, Center of Urban Environment Remediation, Beijing, China); Gao Dawen; Cai Tijiu and Liang Hong. Driving factors on greenhouse gas emissions in permafrost region of Daxing'an Mountains, northeast China: Journal of Geophysical Research: Biogeosciences, 127(3), Article e2021JG006581, illus. incl. 4 tables, 78 ref., March 2022.
Permafrost regions are an important source of greenhouse gases. However, the effects of different permafrost wetland types on greenhouse gas emissions and the driving factors are still unclear in the permafrost region. Here, we selected three typical permafrost wetlands from the Daxing'an Mountains to investigate the effects of permafrost wetland types on greenhouse gas emissions. The cumulative N2O, CO2, and CH4 emissions were 84-122, 657,942-1,446,121, and 173-16,924 kg km-2, respectively. The linear mixed effects model indicated that N2O emissions were significantly affected by the NO3--N content, whereas CO2 emissions were mainly driven by soil temperature, water table level, and NO3--N content. CH4 emissions were affected by soil temperature and water table level. Permafrost wetland types significantly affected the average and cumulative N2O, CO2, and CH4 emissions. The cumulative N2O emissions were highest in the Larix gmelinii - Carex appendiculata (LC) wetland and lowest in the Betula fruticosa Pall. (B) wetland, driven by NO3--N content. The cumulative CO2 emissions were highest in the B wetland and lowest in the L. gmelinii - Ledum palustre var. dilatatum (LL) wetland. The cumulative CH4 emissions from B wetland were significantly higher than those from LL and LC wetlands. The differences in cumulative CO2 and CH4 emissions were driven by the water table level. Our findings indicate that NO3--N content affect the spatial-temporal variation of N2O emissions, whereas water table level influence the spatial-temporal variation of CO2 and CH4 emissions in the permafrost region of the Daxing'an Mountains. Abstract Copyright (2022). American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2021JG006581
2022024436 Pieterek, B. (Adam Mickiewicz University, Institute of Geology, Poznan, Poland); Laban, M.; Ciazela, J. and Muszynski, A. Explosive volcanism in Noctis Fossae on Mars: Icarus, 375, Article 114851, illus. incl. 5 tables, geol. sketch maps, 119 ref., March 15, 2022. Includes appendix.
Based on theoretical considerations, basaltic volcanism of explosive character should be common on Mars. Although the record of explosive volcanic fields on Mars continues to grow, many unexplored volcanic fields remain. In this research, we identified a group of 25 volcanic cones and associated lava flows emplaced in the Noctis Fossae region on Mars. To analyze this volcanic field, we used images from the Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) of Mars Reconnaissance Orbiter (MRO). We interpreted those volcanic cones and their geological history by (1) analyzing their spatial distribution, (2) determining the morphometric parameters, (3) measuring orientations of their summit alignments, and (4) dating these cones along with surrounding lava flows. The identified cones are characterized by various states of preservation from almost fully eroded vent relicts to well-preserved edifices of conical shapes accompanied by short-distance lava flows. Morphological data suggest that the whole set of identified cones likely represent explosive scoria cones. Using the crater count dating method coupled with the structural relationship between the lava flows and volcanic cones, we found that the southern and central cones likely formed >300 Ma, while the northernmost cones between 200 and 50 Ma. These results suggest long-lived volcanism in the studied area active until the latest Amazonian period. In addition, to the present state of knowledge, these cones represent the youngest explosive volcanism in Tharsis and support other findings of young explosive-origin features on Mars. This might shed new light on the magmatic plumbing system of the Tharsis region, although magma sources from Syria Planum, or less likely Valles Marineris, are not excluded. Such magmas of explosive nature are probably rich in volatiles, which might derive from water and/or hydroxyl bearing minerals' or subsurface permafrost deposits. In addition, these magmas might be associated with intensive hydrothermal activity in the region.
DOI: 10.1016/j.icarus.2021.114851
2022024448 Herring, Teddi (University of Calgary, Department of Geoscience, Calgary, AB, Canada); Heagy, Lindsey J.; Pidlisecky, Adam and Cey, Edwin. Hybrid parametric/smooth inversion of electrical resistivity tomography data: Computers & Geosciences, 159, Article 104986, illus. incl. 2 tables, 56 ref., February 2022. Includes appendix.
The standard smooth electrical resistivity tomography inversion produces an estimate of subsurface conductivity that has blurred boundaries, damped magnitudes, and often contains inversion artifacts. In many problems the expected conductivity structure is well constrained in some parts of the subsurface, but incorporating prior information in the inversion is not a trivial task. In this study we developed an electrical resistivity tomography inversion algorithm that combines parametric and smooth inversion strategies. In regions where the subsurface is well constrained, the model was parameterized with only a few variables, while the rest of the subsurface was parameterized with voxels. We tested this hybrid inversion strategy on two synthetic models that contained a well constrained highly resistive or conductive near-surface horizontal layer and a target beneath. In each testing scenario, the hybrid inversion improved resolution of feature boundaries and magnitudes and had fewer inversion artifacts than the standard smooth inversion. A sensitivity analysis showed that the hybrid inversion successfully recovered subsurface features when a range of regularization parameters, initial models, and data noise levels were tested. The hybrid inversion strategy can potentially be expanded to a range of applications including marine surveys, permafrost/frozen ground studies, urban geophysics, or anywhere that prior information allows part of the model to be constrained with simple geometric shapes.
DOI: 10.1016/j.cageo.2021.104986
2022021679 Bao, Zhongwen (University of Waterloo, Department of Earth and Environmental Sciences, Waterloo, ON, Canada); Bain, Jeff; Holland, Steven P.; Wilson, David; Ptacek, Carol J. and Blowes, David W. Hydrogeochemical response of a variably saturated sulfide-bearing mine waste-rock pile to precipitation; a field-scale study in the discontinuous permafrost region of northern Canada: Water Resources Research, 58(1), Article e2021WR031082, illus., 55 ref., January 2022.
Globally, drainage from sulfide-bearing waste-rock piles, containing high concentrations of toxic metal(loid)s, can severely degrade surrounding ecosystems. Waste-rock piles are typically deposited as unsaturated porous media. The complex physical and chemical heterogeneity of waste rock poses significant challenges to the evaluation of internal hydrological, (bio)geochemical, and mineralogical controls on the magnitude and duration of environmental impacts. An operational-scale waste-rock pile located in the discontinuous permafrost region of Northern Canada was well-instrumented and monitored to examine hydrological processes (including precipitation, evaporation, and infiltration), hydrological and thermal responses to freeze-thaw and dry-wet cycles, and concentration-discharge (cQ) relationships in drainage-water quantity and quality. The net infiltration (subtraction of evaporation from precipitation) into the waste-rock pile occurred from May to November, resulting in rainfall-dominated recharge to pore water, surface seepage, and groundwater. Pronounced variations in water content and temperature in response to freeze-thaw and dry-wet cycles and variations in surface topography were observed in regions of the waste-rock pile impacted by preferential flow pathways. In contrast, distinct variations in water content and temperature were not observed in regions of matrix-dominated flow pathways. The cQ relationships show chemodynamically controlled dilution behavior for most dissolved constituents (e.g., SO4, Fe, Pb, Zn, Cu, Ca, Mn) in the drainage. Therefore, hydrological processes and (bio)geochemical and mineralogical reactions both play prominent roles in determining drainage-water chemistry. This work presents an integrated approach to site-specific monitoring and characterization to evaluate remediation and reclamation options for operational-scale waste-rock piles for long-term ecosystem preservation. Abstract Copyright (2021). The Authors.
DOI: 10.1029/2021WR031082
2022024224 Che Lina (Harbin Normal University, Harbin, China); Cheng Muyang; Xing Libo; Cui Yifan and Wan Luhe. Effects of permafrost degradation on soil organic matter turnover and plant growth: Catena (Giessen), 208, Article 105721, illus. incl. 2 tables, geol. sketch map, 23 ref., January 2022.
Continuous climate warming in northeastern China has intensified the melting of permafrost, leading to its degradation. The thawing of permafrost increases the instability of wetland soil organic matter and accelerates decomposition; this will inevitably have a strong impact on the transformation of soil organic matter and the process of vegetation growth. Therefore, the present study used the Xing'an Mountains in Northeast China as the research area. We selected typical marsh areas and analyzed the thickness of the active layer and seasonal frozen soil at different degrees of permafrost degradation. Soil and plant samples (herbs: Carex schumidtii; shrubs: Vaccinium uliginosum; trees: Betula papyrifera) from foliage, roots, and stems were collected at different depths to determine the carbon and nitrogen stable isotope contents in soil and plants. Analysis of variance and multiple linear regression were used to examine the impact of frozen soil degradation on soil organic matter turnover and vegetation growth. The results showed that the thickness of the active layer is increasing, and the amount of seasonal frozen soil is decreasing in the Xing'an Mountains. The d13C, d15N, ed13C, and esoil15N values of different depths of permafrost were significantly different (P<0.05). The foliage, roots, and stems of C. schumidtii, V. uliginosum, and B. papyrifera under different degrees of permafrost degradation were significantly different (P<0.05), except for the d13C value of B. papyrifera roots. Soil isotopic composition, and therefore SOM quality, was dependent on the isotopic composition of incoming biomass (foliage, roots, and stems).
DOI: 10.1016/j.catena.2021.105721
2022024237 Du Ran (Lanzhou University, College of Earth and Environmental Sciences, Laboratory of Western China's Environmental Systems, Lanzhou, China); Peng Xiaoqing; Frauenfeld, Oliver W.; Sun Wen; Liang Benben; Chen Cong; Jin Haodong and Zhao Yaohua. The role of peat on permafrost thaw based on field observations: Catena (Giessen), 208, Article 105772, illus. incl. geol. sketch map, 76 ref., January 2022.
Rising temperatures result in permafrost degradation in cold regions, but with considerable spatial heterogeneity due to local factors including peat. Peat plays an important role in the permafrost carbon cycle by impacting the soil thermal and hydrologic characteristics. Here we use field observations to describe the role of peat on permafrost thaw based on comparisons at two sites: EBoTA characterized by primarily peat, and PT5 with more mineral soils. Compared to PT5, soil temperature at the EBoTA site was lower in the warm season, but higher in the cold season. Freezing onset was generally 0-19 days later at the PT5 site compared to EBoTA throughout the soil column, except at the 0.1 m depth where it occurred 11 days earlier. The average thawing onset at PT5 was 18-96 days earlier. There were 20-119 more freezing days and 19-118 fewer thawing days at EBoTA than at PT5, and the zero annual amplitude and active layer thickness were lower at EBoTA. Finally, the mean annual ground temperature was greater at PT5, and was even above 0°C in three recent years. These results illustrate peat's thermal insulation effect on permafrost due to its low thermal conductivity and high moisture content. Snow depth increases also amplify the insulation effect. These field observations therefore not only verify, but also quantify the protective role of peatlands on permafrost.
DOI: 10.1016/j.catena.2021.105772
2022020356 Kim, Jihoon (Texas A&M University, Harold Vance Department of Petroleum Engineering, College Station, TX); Lee, Joo Yong; Ahn, Tae Woong; Yoon, Hyun Chul; Lee, Jaehyung; Yoon, Sangcheol and Moridis, George J. Validation of strongly coupled geomechanics and gas hydrate reservoir simulation with multiscale laboratory tests: International Journal of Rock Mechanics and Mining Sciences (1997), 149, Article 104958, 48 ref., January 2022. Based on Publisher-supplied data.
We validate a coupled flow-geomechanics simulator for gas hydrate deposits, named T+MAM, performing two meter-scale laboratory experiments of gas hydrates for production by depressurization, replicating the gas hydrate deposit in the Ulleung Basin, East Sea, South Korea. The first experiment with a sand-only specimen is a 1D 1 m-scale depressurization test based on the excess gas method, which represents the grain coating hydrate growth. On the other hand, the second is a 3D 1.5 m-scale test with the excess water method for a sand-mud alternating layer system, representing the pore filling hydrate growth. We measure production and displacement at the top with different depressurization levels. In particular, the 3D test exhibits high coupling strength of substantial deformation induced by incompressibility of water and high deformability of the specimen. For validation, we match pressure, flow rate, and displacement between the experimental data and numerical results. Thus, we identify that T+MAM is a reliable simulator, which can be applied to fields in both permafrost and deep oceanic hydrate deposits of strongly coupled flow and geomechanics systems. This validation also implies that other coupled simulators based on the same coupling formulation as T+MAM can be validated when individual flow and geomechanics simulators are stable and reliable.
DOI: 10.1016/j.ijrmms.2021.104958
2022022844 Varlamov, Stepan Prokopievich (Russian Academy of Sciences, Melnikov Permafrost Institute, Yakutsk, Russian Federation); Skachkov, Yuri Borisovich and Skryabin, Pavel Nikolaevich. Long-term variability in ground thermal state in central Yakutia's Tuymaada Valley: Land (Basel), 10(11), Article 1231, illus. incl. 5 tables, sketch maps, 48 ref., November 2021. This article belongs to the special issue Permafrost landscape response to global change.
This paper presents the results of long-term temperature monitoring at the Yakutsk and Zeleny Lug stations, which are experimental sites, for the thermal state of valley permafrost landscapes under the conditions of modern climate warming. An analysis of the long-term data from meteorological stations in the region clearly showed one of the highest trends of increase in the mean annual air temperature in the north of Russia. Here, we established quantitative regularities in the long-term variability of the ground temperature at the bottom of the active layer and at zero amplitude. The dynamics of the ground temperature of the layer of zero amplitude during climate warming indicate the thermal stability of permafrost. The main regulating factor of the thermal state of grounds in permafrost landscapes is short-term fluctuations in the regime of snow accumulation. Active layer thickness is characterized by low interannual variability, weak climate warming responses, and insignificant trends. The results of studies of the thermal regime of soils can be extended to the same types of valley landscapes in the Lena River, and are a reliable basis for predicting heat transfer in natural and disturbed landscapes.
DOI: 10.3390/land10111231
2022022856 Zhang Yanyu (Harbin Normal University, Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions, Harbin, China); Zang Shuying; Li Miao; Shen Xiangjin and Lin Yue. Spatial distribution of permafrost in the Xing'an Mountains of northeast China from 2001 to 2018: Land (Basel), 10(11), Article 1127, illus. incl. 2 tables, sketch maps, 61 ref., November 2021.
Permafrost is a key element of the cryosphere and sensitive to climate change. High-resolution permafrost map is important to environmental assessment, climate modeling, and engineering application. In this study, to estimate high-resolution Xing'an permafrost map (up to 1 km2), we employed the surface frost number (SFN) model and ground temperature at the top of permafrost (TTOP) model for the 2001-2018 period, driven by remote sensing data sets (land surface temperature and land cover). Based on the comparison of the modeling results, it was found that there was no significant difference between the two models. The performances of the SFN model and TTOP model were evaluated by using a published permafrost map. Based on statistical analysis, both the SFN model and TTOP model efficiently estimated the permafrost distribution in Northeast China. The extent of Xing'an permafrost distribution simulated by the SFN model and TTOP model were 6.88 ´ 105 km2 and 6.81 ´ 105 km2, respectively. Ground-surface characteristics were introduced into the permafrost models to improve the performance of models. The results provided a basic reference for permafrost distribution research at the regional scale.
DOI: 10.3390/land10111127
2022022853 Zhirkov, Aleksandr (Russian Academy of Sciences, Melnikov Permafrost Institute, Yakutsk, Russian Federation); Permyakov, Petr; Wen Zhi and Kirillin, Anatolii. Influence of rainfall changes on the temperature regime of permafrost in central Yakutia: Land (Basel), 10(11), Article 1230, illus. incl. sect., 2 tables, sketch map, 46 ref., November 2021.
Climate change effects, such as melting of glaciers and sea ice in response to rising temperatures, may lead to an increase in global water availability and thus in precipitation. In Central Yakutia, as one of the possible options for climate change, an increase in rainfall is possible, which makes up more than 60% of the annual precipitation. Rainfall is a highly variable meteorological parameter both spatially and temporally. In order to assess its effect on the ground temperature regime in Central Yakutia, we conducted manipulation and numerical experiments with increased rainfall. The manipulation experiment results suggest that a significant (three-fold) increase in rainfall can lower the mean annual ground temperatures locally. The long-term simulation predicts that a 50% increase in rainfall would have a warming effect on the ground thermal regime on a regional scale. For Central Yakutia, infiltration of increased precipitation has been shown to have both warming and cooling effect depending on the area affected.
DOI: 10.3390/land10111230
2022022629 Tian Yahu (Beijing Jiaotong University, School of Civil Engineering, Beijing, China); Yang, Zhaohui; Liu Yuyang; Cai Xiaopei and Shen Yupeng. Long-term thermal stability and settlement of heat pipe-protected highway embankment in warm permafrost regions: Engineering Geology, 292, Article 106269, illus. incl. strat. cols., 32 ref., October 2021.
Warm permafrost is a challenging geological material for infrastructure engineering. This study presents the observed damage, ground temperature, and settlement at varying depths from three-year continuous monitoring of two selected highway embankment segments along the Qinghai-Tibet Highway in warm permafrost areas, including one conventional embankment and the other with heat pipes on the sunny slope side. Field monitoring data reveal that the embankment settlement mainly results from thaw consolidation of warm permafrost, and the permafrost table beneath a conventional embankment is concave-shaped due to the polythermal effects of asphalt pavement. In contrast, the permafrost table underneath the embankment equipped with heat pipes on the sunny side is convex-shaped due to heat pipes' cooling effects. The different causes of longitudinal cracks on the two embankment surfaces were uncovered based on field observed data. Results of coupled hydro-thermal-mechanical model simulation considering climate warming show that while the configurations of heat pipes on both sides of the embankment can generally ensure the long-term thermal stability and limit the differential settlement across the road surface, the one with slanted heat pipes delivers the best performance and is recommended for future applications. Results from this study, including field monitoring data and recommended heat pipe configuration, will be of value for the construction and maintenance of transportation infrastructure in warm permafrost regions.
DOI: 10.1016/j.enggeo.2021.106269
2022021438 Tananaev, Nikita (Russian Academy of Sciences, P. I. Melnikov Permafrost Institute, Yakutsk, Russian Federation); Isaev, Vladislav; Sergeev, Dmitry; Kotov, Pavel and Komarov, Oleg. Hydrological connectivity in a permafrost tundra landscape near Vorkuta, north-European Arctic Russia: Hydrology, 8(3), Article 106, illus. incl. 2 tables, sketch map, 52 ref., September 2021.
Hydrochemical and geophysical data collected during a hydrological survey in September 2017, reveal patterns of small-scale hydrological connectivity in a small water track catchment in the north-European Arctic. The stable isotopic composition of water in different compartments was used as a tracer of hydrological processes and connectivity at the water track catchment scale. Elevated tundra patches underlain by sandy loams were disconnected from the stream and stored precipitation water from previous months in saturated soil horizons with low hydraulic conductivity. At the catchment surface and in the water track thalweg, some circular hollows, from 0.2 to 0.4 m in diameter, acted as evaporative basins with low deuterium excess (d-excess) values, from 2 ppm to 4 ppm. Observed evaporative loss suggests that these hollows were disconnected from the surface and shallow subsurface runoff. Other hollows were connected to shallow subsurface runoff, yielding d-excess values between 12 ppm and 14 ppm, close to summer precipitation. 'Connected' hollows yielded a 50% higher dissolved organic carbon (DOC) content, 17.5±5.3 mg/L, than the 'disconnected' hollows, 11.8±1.7 mg/L. Permafrost distribution across the landscape is continuous but highly variable. Open taliks exist under fens and hummocky depressions, as revealed by electric resistivity tomography surveys. Isotopic evidence supports upward subpermafrost groundwater migration through open taliks under water tracks and fens/bogs/depressions and its supply to streams via shallow subsurface compartment. Temporal variability of isotopic composition and DOC in water track and a major river system, the Vorkuta River, evidence the widespread occurrence of the described processes in the large river basin. Water tracks effectively drain the tundra terrain and maintain xeric vegetation over the elevated intertrack tundra patches.
DOI: 10.3390/hydrology8030106
2022024005 Gao Zeyong (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Niu Fujun; Lin Zhanju and Luo Jing. Fractal and multifractal analysis of soil particle-size distribution and correlation with soil hydrological properties in active layer of Qinghai-Tibet Plateau, China: Catena (Giessen), 203, Article 105373, illus. incl. 3 tables, sketch map, 78 ref., August 2021.
The soil hydrological properties (HPs) in active layers regulate soil water migration and affect the evolution of permafrost and biogeochemical cycles. There is relatively little understanding of the changes in soil HPs as a result of soil particle-size distribution (PSD) in the permafrost regions of the Qinghai-Tibet Plateau. In this study, different land-cover types, namely alpine wet meadow (AWM), extremely degraded wet meadow (EDWM), alpine meadow (AM), degraded alpine meadow (DAM), alpine steppe (AS), and alpine desert (AD), were used to determine the relationships between soil PSD and HPs. Soil HPs were determined using borehole nuclear magnetic resonance, and soil PSD (0-2 mm) was analyzed using fractal and multifractal theory. The results showed that vegetation degradation caused coarse soil particle accumulation in the root zone, reflected by the soil single-fractal dimension (Dv: 2.12-2.50). The Dv values showed significant positive correlations with soil clay and silt content as well as a negative correlation with sand content. Results from the generalized fractal and singularity spectra suggested an even distribution of soil particles in the root zone of the AWM, AM, and AD sites. Vegetation degradation increased the soil PSD capacity dimension (D0), information dimension (D1), correlation dimension, D1/D0 ratio, and Holder exponent of order zero. This was indicative of a narrow soil PSD range and non-uniform soil texture in the root zone. Although capillary water dominated the total soil water content in the alpine soils, soil water composition was also dependent on the vegetation type and soil stratigraphic distribution. Soil particle composition and multifractal dimensions were found to be effective parameters for forecasting soil HPs in the non-root zone of alpine soils. However, the presence of vegetation weakens the relationship between soil PSD and HPs. This study contributes to the accurate evaluation of hydrological and biogeochemical cycles in permafrost regions.
DOI: 10.1016/j.catena.2021.105373
2022023993 Song Yanyu (Chinese Academy of Sciences, Northeast Institute of Geography and Agroecology, Key Laboratory of Wetland Ecology and Environment, Changchun, China); Liu Chao; Song Changchun; Wang Xianwei; Ma Xiuyan; Gao Jinli; Gao Siqi and Wang Lili. Linking soil organic carbon mineralization with soil microbial and substrate properties under warming in permafrost peatlands of northeastern China: Catena (Giessen), 203, Article 105348, illus. incl. 3 tables, 78 ref., August 2021.
Permafrost peatlands are important pools of soil carbon. Soil organic carbon (SOC) mineralization and its temperature sensitivity in permafrost peatlands are crucial for predictions of soil carbon-climate feedback. However, little is known about the changes in SOC mineralization and its mechanism in response to environmental change in the permafrost peatlands of Northeastern China. We collected seven permafrost peatland soils from Greater and Lesser Khingan Mountains in Northeastern China to investigate how the responses of microbes and labile substrates control the mineralization of SOC in the laboratory incubation study. The results show that temperature and sampling sites affected the mineralization of SOC. Elevated temperatures significantly increased the rate of carbon mineralization across the peatland soils. The mean sensitivity of SOC mineralization to temperature (Q10 value) was 2.96. The increase in substrate availability and microbial abundance in parallel with the increase in temperature is responsible for the high rates of decomposition of the organic carbon pools. We found that the mineralization of soil carbon positively correlated with the concentrations of soil dissolved organic carbon (DOC), NH4+-N, NO3--N, as well as the abundances of bacteria, fungi, methanotrophs and nirK denitrifiers. Moreover, the content of DOC positively correlated with the abundances of soil bacteria, methanotrophs and nirK denitrifiers, indicating that the influences of soil microbial abundances on carbon mineralization were strongly mediated by the availability of carbon substrates. Our findings provide novel insights into the effects of increasing temperatures on the relationship between microbial communities and labile substrates and their roles in carbon decomposition in permafrost peatlands.
DOI: 10.1016/j.catena.2021.105348
2022022511 Zheng, Wang (University of Toronto, Department of Earth Sciences, Toronto, ON, Canada); Chandan, Priyanka; Steffen, Alexandra; Stupple, Geoff; De Vera, Joan; Mitchell, Carl P. J.; Wania, Frank and Bergquist, Bridget A. Mercury stable isotopes reveal the sources and transformations of atmospheric Hg in the High Arctic: Applied Geochemistry, 131, Article 105002, illus. incl. sketch map, 79 ref., August 2021.
The Arctic plays a critical role in the global Hg cycle as both a sink of Hg and, in response to rapid global warming, an emerging source of Hg due to release from permafrost and glaciers. Human activities have led to significant mercury (Hg) contamination in the Arctic over many decades, potentially impacting the health of Arctic ecosystems and indigenous people. Thus, it is crucial to understand the sources and transformations of Hg in the Arctic in order to predict how Hg behaves as emissions and the global climate change. Here we examine Hg stable isotopes in atmospheric particulate Hg (PHg), gaseous elemental Hg (GEM) and surface snow in the high Arctic (Alert, Canada) during polar spring from 2011 to 2015, in order to trace the sources of atmospheric Hg and its fate in Arctic surface environment. Isotope signatures of GEM (d202Hg = 0.67 ± 0.24 ppm, D199Hg = -0.23 ± 0.04 ppm, D200Hg = -0.06 ± 0.04 ppm, 2SD) are similar to the average Northern Hemisphere background, suggesting that GEM in the high Arctic atmosphere is well mixed with those from lower latitudes. Surprisingly, the isotope composition of PHg has negative D199Hg, which is similar to GEM but distinct from the positive D199Hg typically observed for oxidized Hg species elsewhere. Furthermore, Hg in surface snow shows more negative MIF than PHg, indicating post-depositional loss of Hg via photoreduction. We suggest that PHg is primarily sourced from in situ oxidation of GEM and subsequent scavenging by particles, and thus inherited the isotope composition of GEM when the oxidation is near-complete. The photoreduction re-emission of Hg from snow is strongly affected by Hg speciation, but the overall extent of re-emission (20 ± 31%) is lower than previous estimations for other locations, suggesting potentially a greater loading of Hg to Arctic ecosystem via snowmelt.
DOI: 10.1016/j.apgeochem.2021.105002
2022020428 Campbell-Heaton, Kethra (University of Ottawa, Department of Geography, Environment and Geomatics, Ottawa, ON, Canada); Lacelle, Denis; Fisher, David and Pollard, Wayne. Holocene ice wedge formation in the Eureka Sound Lowlands, high Arctic Canada: Quaternary Research, 102, p. 175-187, July 2021. Indexed from publisher-supplied data.
Ice wedges are ubiquitous periglacial features in permafrost terrain. This study investigates the timing of ice wedge formation in the Fosheim Peninsula (Ellesmere and Axel Heiberg Islands). In this region, ice wedge polygons occupy ~50% of the landscape, the majority occurring below the marine limit in the Eureka Sound Lowlands. Numerical simulations suggest that ice wedges may crack to depths of 2.7-3.6 m following a rapid cooling of the ground over mean winter surface temperatures of -18°C to -38°C, corresponding to the depth of ice wedges in the region. The dissolved organic carbon (DOC)/Cl molar ratios suggest that the DOC in the ice wedges is sourced from snowmelt and not from leaching of the active layer. Based on 32 14CDOC measurements from 15 ice wedges, the wedges were likely developing between 9000-2500 cal yr BP. This interval also corresponds to the period of peat accumulation in the region, a proxy of increased moisture. Considering that winter air temperatures remained favorable for ice wedge growth throughout the Holocene, the timing of ice wedge formation reflects changes in snowfall. Overall, this study provides the first reconstruction of ice wedge formation from a high Arctic polar desert environment.
DOI: 10.1017/qua.2020.126
2022024024 Qiao Baojin (Zhengzhou University, School of Geoscience and Technology, Zhengzhou, China); Nie Bingkang; Liang Changmao; Xiang Longwei and Zhu Liping. Spatial difference of terrestrial water storage change and lake water storage change in the inner Tibetan Plateau: Remote Sensing, 13(10), 18 p., illus. incl. 3 tables, geol. sketch map, 82 ref., May 2021. Part of a special issue entitled Remote sensing applications for hydrogeography and climatology, edited by Schneider, K. and Hendricks Franssen, H. J.
Water resources are rich on the Tibetan Plateau, with large amounts of glaciers, lakes, and permafrost. Terrestrial water storage (TWS) on the Tibetan Plateau has experienced a significant change in recent decades. However, there is a lack of research about the spatial difference between TWSC and lake water storage change (LWSC), which is helpful to understand the response of water storage to climate change. In this study, we estimate the change in TWS, lake water storage (LWS), soil moisture, and permafrost, respectively, according to satellite and model data during 2005-2013 in the inner Tibetan Plateau and glacial meltwater from previous literature. The results indicate a sizeable spatial difference between TWSC and LWSC. LWSC was mainly concentrated in the northeastern part (18.71 ± 1.35 Gt, 37.7% of the total) and southeastern part (22.68 ± 1.63 Gt, 45.6% of the total), but the increased TWS was mainly in the northeastern region (region B, 18.96 ± 1.26 Gt, 57%). Based on mass balance, LWSC was the primary cause of TWSC for the entire inner Tibetan Plateau. However, the TWS of the southeastern part increased by 3.97 ± 2.5 Gt, but LWS had increased by 22.68 ± 1.63 Gt, and groundwater had lost 16.91 ± 7.26 Gt. The increased TWS in the northeastern region was equivalent to the increased LWS, and groundwater had increased by 4.47 ± 4.87 Gt. Still, LWS only increased by 2.89 ± 0.21 Gt in the central part, and the increase in groundwater was the primary cause of TWSC. These results suggest that the primary cause of increased TWS shows a sizeable spatial difference. According to the water balance, an increase in precipitation was the primary cause of lake expansion for the entire inner Tibetan Plateau, which contributed 73% (36.28 Gt) to lake expansion (49.69 ± 3.58 Gt), and both glacial meltwater and permafrost degradation was 13.5%.
DOI: 10.3390/rs13101984
2022024028 Serban, Raul-David (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soils, Lanzhou, China); Serban, Mihaela; He Ruixia; Jin Huijun; Li Yan; Li Xinyu; Wang Xinbin and Li Guoyu. 46-year (1973-2019) permafrost landscape changes in the Hola Basin, Northeast China using machine learning and object-oriented classification: Remote Sensing, 13(10), 19 p., illus. incl. 2 tables, geol. sketch map, 69 ref., May 2021. Includes 1 appendix; part of a special issue entitled Monitoring of forest ecological environment based on remote sensing technology; Part II, edited by Hirata, Y.
Land use and cover changes (LUCC) in permafrost regions have significant consequences on ecology, engineered systems, and the environment. Obtaining more details about LUCC is crucial for sustainable development, land conservation, and environment management. The Hola Basin (957 km2) in the northernmost part of Northeast China, a boreal forest landscape underlain by discontinuous, sporadic, and isolated permafrost, was selected for the case study. The LUCC was analyzed using the Landsat archive of satellite images from 1973 to 2019. A thematic change detection analysis was performed by combining the object-based image analysis (OBIA) and the Support Vector Machine (SVM) algorithm. Four types of LUCC (forest, grass, water, and anthropic) were extracted with an overall accuracy of 80% for 1973 and >90% for 1986, 2000, and 2019. Forest, the dominant class (750 km2 in 1973), declined by 88 km2 (11.8%) from 1973 to 1986 but had a recovery of 78 km2 (12.5%) from 2000 to 2019. Grass, the second-largest class (187 km2 in 1973), increased by 86 km2 (46.5%) between 1973 and 1986 and decreased by 90 km2 (40%) between 2000 and 2019. The anthropic class continuously increased from 10 km2 (1973) to 37 km2 (2019). Major features in LUCC are attributed to rapid population growth, resource exploitation, agriculture intensification, economic development, and frequent forest fires. Under a pronounced climate warming, these drivers have been accelerating the degradation of permafrost, subsequently triggering natural hazards and deteriorating the ecological environment. This study represents a benchmark for sustainable LUCC management in the Hola Basin, Northeast China.
DOI: 10.3390/rs13101910
2022024015 Yin Guoan (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Luo Jing; Niu Fujun; Zhou Fujun; Meng Xianglian; Lin Zhanju and Liu Minghao. Spatial analyses and susceptibility modeling of thermokarst lakes in permafrost landscapes along the Qinghai-Tibet engineering corridor: Remote Sensing, 13(10), 18 p., illus. incl. 2 tables, geol. sketch maps, 67 ref., May 2021.
Thermokarst lakes (TLs) caused by the thaw of massive ground ice in ice-rich permafrost landscapes are increasing and have strong impacts on the hydro-ecological environment and human infrastructure on the Qinghai-Tibet Plateau (QTP), however, its spatial distribution characteristics and environmental controls have not been underrepresented at the local scale. Here, we analyzed the spatial distribution of small TLs along the Qinghai-Tibet Engineering Corridor (QTEC) based on high-resolution (up to 2.0 m) satellite images. The TLs gathered in the plains and upland plateau and covered 8.3% of the QTEC land. We deployed a random-frost method to investigate the suitable environmental conditions for TLs. Climate including summer rainfall and the air temperature was the most important factor controlling the TL distribution, followed by topography and soil characteristics that affected the ground ice content. TL susceptibility was mapped based on the combinations of climate, soil, and topography grid data. On average, around 20% of the QTEC area was in a high to very-high-susceptibility zone that is likely to develop TLs in response to climate change. This study improved the understanding of controlling factors for TL development but also provided insights into the conditions of massive ground ice and was helpful to assess the impacts of climate change on ecosystem processes and engineering design.
DOI: 10.3390/rs13101974
2022023397 Scandroglio, Riccardo (Technical University Munich, Munich, Germany); Draebing, Daniel; Offer, Maike and Krautblatter, Michael. 4D quantification of alpine permafrost degradation in steep rock walls using a laboratory-calibrated electrical resistivity tomography approach: in Near-surface geophysics for geohazard assessment (Uhlemann, Sebastian, editor; et al.), Near Surface Geophysics, 19(2), p. 241-260, illus. incl. 3 tables, sketch map, 66 ref., April 2021.
The warming of rock permafrost affects mechanical stability and hydro-cryostatic pressures in rock walls. The coincident decrease in slope stability frequently affects infrastructure by creep and subsidence and promotes the generation of rockfalls and rockslides. The increasing hazard posed by warming permafrost rock walls and the growing exposure of infrastructure and individuals create a demand for quantitative monitoring methods. Laboratory-calibrated electrical resistivity tomography provides a sensitive record for frozen versus unfrozen bedrock, presumably being the most accurate quantitative monitoring technique in permafrost areas where boreholes are not available. The data presented here are obtained at the permafrost-affected and unstable Steintaelli Ridge at 3100 m a.s.l. and allow the quantification of permafrost changes in the longest electrical resistivity tomography time series in steep bedrock. Five parallel transects across the rock ridge have been measured five times each, between 2006 and 2019, with similar hardware. Field measurements were calibrated using temperature-resistivity laboratory measurements of water-saturated rock samples from the site. A 3D time-lapse inversion scheme is applied in the boundless electrical resistivity tomography (BERT) software for the inversion of the data. To assess the initial data quality, we compare the effect of data filtering and the robustness of final results with three different filters and two time-lapse models. We quantify the volumetric permafrost distribution in the bedrock and its degradation in the last decades. Our data show mean monthly air temperatures to increase from -3.4°C to -2.6°C between 2005-2009 and 2015-2019, respectively, while simultaneously permafrost volume degraded on average from 6790 m3 (±640 m3 rock in phase-transition range) in 2006 to 3880 m3 (±1000 m3) in 2019. For the first time, we provide a quantitative measure of permafrost degradation in unstable bedrock by using a temperature-calibrated 4D electrical resistivity tomography. Our approach represents a fundamental benchmark for the evaluation of climate change effects on bedrock permafrost. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/nsg.12149
2022023650 Brothers, S. (University of Guelph, School of Environmental Sciences, Guelph, ON, Canada); Bowes, D.; Pearse, W. D.; Tank, S.; Vanengen, R. and Sibley, P. Declining summertime pCO2 in tundra lakes in a granitic landscape: Global Biogeochemical Cycles, 35(2), Article e2020GB006850, illus., 86 ref., February 2021.
As climate change accelerates, positive feedback loops could establish between atmospheric warming and increasing greenhouse gas (GHG) emissions from natural ecosystems. Of particular interest are high-latitude environments, many of which contain large stores of organic carbon and have experienced decades of accelerated warming. Freshwater ecosystems situated in carbon-rich Arctic landscapes are predicted to respond to warming with higher respiration rates relative to primary production rates, increasing their carbon dioxide partial pressure (pCO2) and thus CO2 emissions to the atmosphere. However, large areas of shallow soil/bedrock occur in Arctic and sub-Arctic regions and could respond differently due to the lower availability of stored carbon. Here, we used pH and alkalinity to calculate 23 years (1994-2017) of summertime (July and August) pCO2 and CO2 fluxes for 19 sub-Arctic tundra lakes located on the shallow-bedrock granitic Canadian Shield in Nunavut, Canada, and found a significant decline in CO2 emissions. Regional precipitation did not change over this period, yet dramatic increases in pH, conductivity, and total alkalinity indicated that longer ice-free periods and changes in primary production, both functions of accelerated climate warming at higher latitudes, may be suppressing lacustrine CO2 emissions. Northern lakes overlying differing geological landscapes may thus be responding in contrasting ways in terms of pCO2 and CO2 fluxes, with potential major implications for regional carbon budgets and predicted climate change feedbacks. Abstract Copyright (2021), American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2020GB006850
2022020867 Curran, Janet H. (U. S. Geological Survey, Anchorage, AK) and Biles, Frances E. Identification of seasonal streamflow regimes and streamflow drivers for daily and peak flows in Alaska: Water Resources Research, 57(2), Paper no. e2020WR028425, illus. incl. 1 table, 87 ref., January 2021.
Alaska is among northern high-latitude regions where accelerated climate change is expected to impact streamflow properties, including seasonality and primary flow drivers. Evaluating changes to streamflow, including flood characteristics, across this large and diverse environment can be improved by identifying the distribution and influence of flow drivers. Using metrics of mean monthly streamflow data from 253 streamgages, seasonal flow regimes were clustered to guide identification of seasonal flow drivers and form hydrologic groups for identification of peak-flow populations. Nine seasonally distinct subclasses described variability within three classes dominated by (mostly fall) rainfall, (spring) snowmelt, and (summer) high-elevation melt. The most glacierized basins exclusively grouped into high-elevation melt subclasses, and less glacierized basins sometimes exhibited seasonal patterns aligned with rainfall-dominated and snowmelt-dominated regimes. Peak-flow populations varied by subclass from dominant rainfall or dominant snowmelt to mixed rainfall-snowmelt or mixed rainfall, snowmelt, and high-elevation melt. Within subclasses, rainfall generated higher mean peak flows (relative to mean annual flow) than snowmelt or high-elevation melt. Seasonal flow regimes showed clear but complex associations with basin characteristics, primarily elevation and winter temperature, and with geographic location. These dependencies provided elevation-based analogies for changes associated with warming and insights for seasonal flow regime prediction and hydrologic region delineation. These results provide a spatially comprehensive perspective on seasonal streamflow drivers across Alaska from historical data and serve as an important historical basis for analysis. Abstract Copyright Published 2020. This article is a U.S. Government work and is in the public domain in the USA.
DOI: 10.1029/2020WR028425
2022020822 Li, Dongfeng (National University of Singapore, Department of Geography, Kent Ridge, Singapore); Overeem, Irina; Kettner, Albert J.; Zhou Yinjun and Lu, Xixi. Air temperature regulates erodible landscape, water, and sediment fluxes in the permafrost-dominated catchment on the Tibetan Plateau: Water Resources Research, 57(2), Paper no. e2020WR028193, illus., 54 ref., January 2021.
Approximately 40% of the Tibetan Plateau (TP) is underlain by continuous permafrost, yet its impact on fluvial water and sediment dynamics remains poorly investigated. Here we show that water and sediment dynamics in the permafrost-dominated Tuotuohe basin on the TP are driven by air temperature and permafrost thaw, based on 33-year daily in situ observations (1985-2017). Air temperature regulates the seasonal patterns of discharge and suspended sediment concentration (SSC) by controlling the changes in active contributing drainage area (ACDA, the unfrozen erodible landscape that contributes hydrogeomorphic processes within a catchment) and governing multiple thermal processes such as glacier-snow melt and permafrost thaw. Rainstorms determine the short-lived fluvial extreme events by intensifying slope processes and channel erosion and likely also by enhancing thaw slumps. Furthermore, the SSCs at equal levels of discharges are lower in autumn (September-October) than in spring (May-June) and summer (July-August). This reduced sediment availability in autumn can possibly be attributed to the increased supra-permafrost groundwater runoff and the reduced surface runoff and erosion. Due to rapid climate warming, the ACDA has increased significantly from 1985 to 2017, implying expanding erodible landscapes for hydrogeomorphic processes. As a result, the fluvial water and sediment fluxes have substantially increased. In a warmer and wetter future for the TP, the fluvial sediment fluxes of similar permafrost-underlain basins will continue to increase with expanding erodible landscapes and intensifying thermal and pluvial-driven geomorphic processes. Thus, permafrost thaw should be considered as an important driver of past and future water and sediment changes for the TP. Abstract Copyright (2021), American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2020WR028193
2022020861 Sjoberg, Ylva (University of Copenhagen, Department of Geosciences and Natural Resource Management,, Copenhagen, Denmark); Jan, Ahmad; Painter, Scott L.; Coon, Ethan T.; Carey, Michael P.; O'Donnell, Jonathan A. and Koch, Joshua C. Permafrost promotes shallow groundwater flow and warmer headwater streams: Water Resources Research, 57(2), Paper no. e2020WR027463, illus. incl. 3 tables, 90 ref., January 2021.
The presence of permafrost influences the flow paths of water through Arctic landscapes and thereby has the potential to impact stream discharge and thermal regimes. Observations from 11 headwater streams in Alaska showed that July water temperatures were higher in catchments with more near-surface permafrost. We apply a fully coupled cryohydrology model to investigate if the impact of permafrost on flow path depth could cause the same pattern in temperatures of groundwater discharging from hillslopes to streams. The model simulates surface energy and water balances, snow, and subsurface water and energy balances for two-dimensional hillslope model cases with varying permafrost extent. We find that hillslopes with continuous permafrost have more shallow flow paths and twice as high rates of evapotranspiration, compared to hillslopes with no permafrost. For our simulated cases, 6.7% of the horizontal water flux moves through the top organic soil layers when there is continuous permafrost, while only 0.5% moves through organic layers without permafrost. The deeper flow paths in permafrost-free simulations buffer seasonal temperature extremes, so that summer groundwater discharge temperatures are highest with continuous permafrost. Our results suggest that permafrost thawing alters groundwater flow paths and can lead to decreases in summer stream temperatures and reductions in evapotranspiration in headwater catchments. These changes are of potential importance for stream biotic components of ecosystems, however, the full impact remains unknown. Abstract Copyright (2020), The Authors.
DOI: 10.1029/2020WR027463
2022020448 Thiry, Médard (PSL Research University, MINES ParisTech, Center of Geosciences, Fontainebleau, France); Innocent, Christophe; Girard, Jean-Pierre; Milnes, Anthony Richard; Franke, Christine and Guillon, Sophie. Sand calcites as a key to Pleistocene periglacial landscapes: Quaternary Research, 101, p. 225-244, 2021. Indexed from publisher-supplied data.
We tested the potential for sand calcites to serve as a novel paleoclimate archive by investigating their age and formation conditions. Fontainebleau sand calcites are Pleistocene in age (based on 14C and U-Th dating) and were primarily formed during glacial periods. d13C values increase with the depth at which these sand calcites formed, consistent with open and closed CO2 systems. Interpretation of the d18O-T relationship in sand calcites points primarily to their formation at a low temperature, around 2°C in shallow ground water and at about 9°C in deeper ground-water settings. Their occurrence, characteristics, and compositions suggest crystallization from paleo-ground waters in permafrost environments. Crystallization of sand calcites was triggered by degassing of cold carbonate-containing surface waters as they infiltrated warmer subsurface ground-water environments. We consider sand calcites to be important indicators of interactions between meteoric water and ground water in Pleistocene periglacial landscapes. Their disposition may point to specific features of periglacial landscapes, and their ages could permit an assessment of landscape incision rates. Large crystals and zoned spheroliths may, in fact, encapsulate continuous high-resolution records of continental glacial and periglacial paleoenvironments.
DOI: 10.1017/qua.2020.98
2022024188 Ji, Xiaowen (Saint Petersburg State University, Department of Applied Ecology, St. Petersburg, Russian Federation); Abakumov, Evgeny; Tomashunas, Vitaly; Polyakov, Vyacheslav and Kouzov, Sergey. Geochemical pollution of trace metals in permafrost-affected soil in the Russian Arctic marginal environment: in Soil contamination and human health; Part 3 (Bech, Jaume, editor; et al.), Environmental Geochemistry and Health, 42(12), p. 4407-4429, illus. incl. 3 tables, sketch map, 95 ref., December 2020.
The Arctic marginal environment has been considered as far from industrial areas and low population. During June-July of 2016 "Russian High Latitude" expedition, 93 samples of soil genetic horizon from 25 soil profiles dug till frozen ground were sampled from 8 islands and 2 capes of the Russian Arctic without direct anthropogenic influences. Nine trace metals (Pb, Cd, Cu, Ni, Co, Zn, Fe, Mn and Hg) were measured and quantified by energy-dispersive X-ray analysis for elemental concentrations. Through analysis of divided soil groups (Haplothels, Turbels, Historthels), the factors of organic matter and cryoturbation had a significant influence on metals' distribution except for Fe and Mn. From summarized soil master horizons (O, A, B, C), Fe and Mn are abundant in all horizons suggesting as geochemical background values. Cu, Pb, Co and Ni are distributed specifically in different horizons with leaching and accumulation process, whereas Hg is evenly disturbed in all horizons. The correlation analysis reveals that distribution of most metals in present soils is highly depended on soil properties (pH, TOC, clay and silt). Li was selected as normalizing element for metals' concentrations from mineral layers to establish geochemical baseline concentrations. The concentrations of trace metals have been assessed by geoaccumulation index (Igeo) and enrichment factor, showing only Co and Zn are moderately polluted and slightly polluted, and Co, Cu, Zn and Pb are enriched in topsoil. Other indices as modified degree of contamination (mCdegree) and pollution load index (PLI), mCdegree show moderate degree of pollution and PLI shows unpolluted to moderate pollution load. The ecological risk indices, e.g., ecological risk factor (Er) and potential ecological risk index, show low ecological risk potential.
DOI: 10.1007/s10653-020-00587-2
2022023587 Bradak, Balazs (University of Burgos, Department of Physics, Burgos, Spain); Seto, Yusuke; Chadima, Martin; Kovacs, Jozsef; Tanos, Peter; Ujvari, Gabor and Hyodo, Masayuki. Magnetic fabric of loess and its significance in Pleistocene environment reconstructions: Earth-Science Reviews, 210, Article 103385, illus. incl. block diags., sketch map, 2 tables, strat. col., 156 ref., November 2020.
A summary of approximately three decades and greater than thirty loess magnetic fabric studies is presented here. The revised studies cover various loess regions from the Chinese Loess Plateau across the European Loess Belt to Alaska. Although there is still an ongoing argument about the feasibility of the magnetic fabric of loess in paleowind reconstructions, the determination of prevailing wind direction during various periods of the Pleistocene is the main goal of magnetic anisotropy analysis of the revised loess successions. The magnetic fabric analysis of loess from Chinese Loess Plateau provided significant information about the characteristics of paleomonsoon in East Asia, and the results from other loess regions, such as Alaska, the European Loess Belt, and Siberia, are also promising. As it is shown in this review, the synthesis of the paleowind direction results from the studied profiles may already provide a significant foundation for future climate models by the reconstruction of key climate centres and main continental level wind tracks. Besides the reconstruction of prevailing paleowind directions, there are numerous loess magnetic fabric studies using magnetic anisotropy parameters in the reconstruction of the characteristics of long-term climate trends, climate transitions and glacial-interglacial cycles. There are some lesser known aspects contributing to magnetic fabric of loess, such as the influence of various types of magnetic contributors on the overall fabric (i.e. the study of sub-fabrics) and their role in environment reconstruction. Besides the identification of aeolian magnetic fabric, not so many studies focus on the magnetic anisotropy characteristics of materials, possibly developed by water-lain sedimentation, pedogenesis, mass movements and permafrost activity.Novel results from Hungarian loess, especially from Paks, connected to some of the latter topics are also presented. Such topics includes the analysis of the nanofabric in paleosols, developed by pedogenesis, the comparison of magnetic fabric, formed during high energy transportation by aeolian or aquatic agents, and the periodicity analysis of magnetic parameters during the early Middle Pleistocene. New research lines, introduced in this review, may inspire new researches, and provide new perspectives for the next generation of magnetic anisotropy studies of loess successions.
DOI: 10.1016/j.earscirev.2020.103385
2022023581 Heslop, J. K. (GFZ German Research Centre for Geosciences, Section 3.7 Geomicrobiology, Potsdam, Germany); Walter Anthony, K. M.; Winkel, M.; Sepulveda-Jauregui, A.; Martinez-Cruz, K.; Bondurant, A.; Grosse, G. and Liebner, S. A synthesis of methane dynamics in thermokarst lake environments: Earth-Science Reviews, 210, Article 103365, illus. incl. sketch map, sects., 106 ref., November 2020.
Greenhouse gas emissions from physical permafrost thaw disturbance and subsidence, including the formation and expansion of thermokarst (thaw) lakes, may double the magnitude of the permafrost carbon feedback this century. These processes are not accounted for in current global climate models. Thermokarst lakes, in particular, have been shown to be hotspots for emissions of methane (CH4), a potent greenhouse gas with 32 times more global warming potential than carbon dioxide (CO2) over a 100-year timescale. Here, we synthesize several studies examining CH4 dynamics in a representative first-generation thermokarst lake (Vault Lake, informal name) to show that CH4 production and oxidation potentials vary with depth in thawed sediments beneath the lake. This variation leads to depth-dependent differences in both in situ dissolved CO2:CH4 ratios and net CH4 production responses to additional warming. Comparing CH4 production, oxidation, and flux values from studies at Vault Lake suggests up to 99% of produced CH4 is oxidized and/or periodically entrapped before entering the atmosphere. We summarize these findings in the context of CH4 literature from thermokarst lakes and identify future research directions for incorporating thermokarst lake CH4 dynamics into estimates of the permafrost carbon feedback.
DOI: 10.1016/j.earscirev.2020.103365
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The USPA is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute (AGI), with support from the National Science Foundation (NSF), has migrated the previous Cold Regions Bibliography to a new platform. Included are the USPA supported PMAs dating back to 2011. The Bibliography is searchable at 
