Thaw Depth Research Articles

Validation of Soil Detachment Rate Equations on Spring Thaw Period Slopes: Insights From Sediment Concentration and Transport Capacity

AbstractSoil detachment plays a central role in the formulation of soil erosion models, particularly for the simulation and prediction of erosion in cold climates during the thaw period. This research attempts to elucidate the mechanisms of soil detachment on spring thaw period slopes through comprehensive flume experiments, coupled with the application of rare earth element (REE) tracer, investigating the relationships between soil detachment rates, sediment concentration and sediment transport capacity. Observations indicate a nuanced response of soil detachment rate and sediment concentration to scour duration, characterized by an initial increase, subsequent decrease and eventual equilibrium. As thaw depth increases, the primary source of eroded sediment gradually shifts from the upper slope to the mid‐slope. Soil detachment rate was affected by sediment concentration, flow discharge, slope gradient, thawing depth, and slope positions. Furthermore, our analysis reveals a power function relationship (R2 = 0.846) between soil detachment rate, effective shear stress, and sediment transport rate and capacity. These results provide valuable insights into the modeling and prediction of soil erosion processes on brown soil slopes subjected to spring thaw period cycles.

Environmental drivers and remote sensing proxies of post-fire thaw depth in eastern Siberian larch forests

Abstract. Boreal fire regimes are intensifying because of climate change, and the northern parts of boreal forests are underlain by permafrost. Boreal fires combust vegetation and organic soils, which insulate permafrost, and as such deepen the seasonally thawed active layer and can lead to further carbon emissions to the atmosphere. Current understanding of the environmental drivers of post-fire thaw depth is limited but of critical importance. In addition, mapping thaw depth over fire scars may enable a better understanding of the spatial variability in post-fire responses of permafrost soils. We assessed the environmental drivers of post-fire thaw depth using field data from a fire scar in a larch-dominated forest in the continuous permafrost zone in eastern Siberia. Particularly, summer thaw depth was deeper in burned (mean=127.3 cm, standard deviation (SD) = 27.7 cm) than in unburned (98.1 cm, SD=26.9 cm) landscapes 1 year after the fire, yet the effect of fire was modulated by landscape and vegetation characteristics. We found deeper thaw in well-drained upland, in open and mature larch forest often intermixed with Scots pine, and in high-severity burns. The environmental drivers basal area, vegetation density, and burn depth explained 73.3 % of the measured thaw depth variability at the study sites. In addition, we evaluated the relationships between field-measured thaw depth and several remote sensing proxies. Albedo, the differenced normalized burn ratio (dNBR), and the pre-fire normalized difference vegetation index (NDVI) derived from Landsat 8 imagery together explained 66.3 % of the variability in field-measured thaw depth. Moreover, land surface temperature (LST) displayed particularly strong correlations with post-fire thaw depth (r=0.65, p<0.01). Based on these remote sensing proxies and multiple linear regression analysis, we estimated thaw depth over the entire fire scar. Our study reveals some of the governing processes of post-fire thaw depth development and shows the capability of Landsat imagery to estimate post-fire thaw depth at a landscape scale.

Permafrost Thawing and Estimates of Vulnerable Carbon in the Northern High Latitude

AbstractThe degradation of permafrost in the Northern Hemisphere is expected to persist and potentially worsen as the climate continues to warm. Thawing permafrost results in the decomposition of organic matter frozen in the ground, which stores large amounts of soil organic carbon (SOC), leading to carbon being emitted into the atmosphere in the form of carbon dioxide and methane. This process could potentially contribute to positive feedback between global climate change and permafrost carbon emissions. Accurate projections of permafrost thawing are key to improving our estimates of the global carbon budget and future climate change. Using data from the latest generation of climate models (CMIP6), this paper explores the challenges involved in assessing the annual active layer thickness (ALT), defined as the maximum annual thaw depth of permafrost, and estimated carbon released under various Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). We find that the ALT estimates derived from CMIP6 model soil temperatures show significant deviations from the observed ALT values. This could lead to inconsistent estimates of carbon release under climate change. We propose a simplified approach to improve the estimate of the changes in ALT under future climate projections. These predicted ALT changes, combined with present-day observations, are used to estimate vulnerable carbon under future climate projections. CMIP6 models project ALT changes of 0.1–0.3 m per degree rise in local temperature, resulting in an average deepening of approx. 1.2–2.1 m in the northern high latitudes under different scenarios. With increasing temperatures, permafrost thawing starts in Southern Siberia, Northern Canada, and Alaska, progressively extending towards the North Pole by the end of the century under high emissions scenarios (SSP5-8.5). Using projections of ALT changes and vertically resolved SOC data, we estimate the ensemble mean of decomposable carbon stocks in thawed permafrost to be approximately 115 GtC (gigatons of carbon in the form of CO2 and CH4) under SSP1-2.6, 180 GtC under SSP2-4.5, 260 GtC under SSP3-7.0, and 300 GtC under SSP5-8.5 by the end of the century.

Formation and evolution of thermokarst landslides in the Qinghai-Tibet Plateau, China

Thermokarst landslide (TL) activity in the Qinghai-Tibet Plateau (QTP) is intensifying due to climate warming-induced permafrost degradation. However, the mechanisms driving landslide formation and evolution remain poorly understood. This study investigates the spatial distribution, annual frequency, and monthly dynamics of TLs along the Qinghai-Tibet engineering corridor (QTEC), in conjunction with in-situ temperature and rainfall observations, to elucidate the interplay between warming, permafrost degradation, and landslide activity. Through the analysis of high-resolution satellite imagery and field surveys, we identified 1298 landslides along the QTEC between 2016 and 2022, with an additional 386 landslides recorded in a typical landslide-prone sub-area. In 2016, 621 new active-layer detachments (ALDs) were identified, 1.3 times the total historical record. This surge aligned with unprecedented mean annual and August temperatures. The ALDs emerged primarily between late August and early September, coinciding with maximum thaw depth. From 2016 to 2022, 97.8 % of these ALDs evolved into retrogressive thaw slumps (RTSs), identified as active landslides. Landslides typically occur in alpine meadows at moderate altitudes and on gentle northward slopes. The thick ice layer near the permafrost table serves as the material basis for ALD occurrence. Abnormally high temperature significantly increased the active layer thickness (ALT), resulting in melting of the ice layer and formation of a thawed interlayer, which was the direct causing factor for ALD. By altering the local material, micro-topography, and thermal conditions, ALD activity significantly increases RTS susceptibility. Understanding the mechanisms of ALD formation and evolution into RTS provides a theoretical foundation for infrastructure development and disaster mitigation in extreme environments.

Investigating soil properties and their effects on freeze-thaw processes in a thermokarst lake region of Qinghai-Tibet Plateau, China

Soil parameters form the foundation of hydrogeological research and are crucial for studying engineering construction and maintenance, climate change, and ecological environment effects in cold regions. However, the soil properties in the permafrost region of the Qinghai–Tibet Plateau (QTP) remain unclear. Hence, in this study, soil temperature (Ts), volumetric specific heat capacity (C), thermal conductivity (K), thermal diffusivity (D), soil water content (SWC), electric conductivity (EC), vertical (Kv) and horizontal (Kh) saturated hydraulic conductivity, bulk density (ρb), and soil texture near the Qinghai-Tibet Railway were measured, and their effects on the freeze-thaw process were evaluated. The results revealed a predominantly sandy loam soil texture, with Kh and Kv showing strong spatial variability, while the other parameters presented moderate spatial variability. Thermokarst lake had a limited influence on D, C, K, and ρb but significantly reduced Kh and Kv. Groundwater affected SWC, Ts, and EC. The model results showed that all parameters indicated small sensitivities to the maximum thawing depth (MTD), with MTD positively responding to all parameters except for Kv and porosity (ρp). Except for Kh and Kv, all parameters showed high sensitivities to the time from starting to complete freezing (TSCF). TSCF responded positively to C, ρp, and density (ρd) and negatively to K and Kh. This study expanded the quantification of soil properties in the QTP, which can help improve the accuracy of cryohydrogeologic models, thus guiding the construction and maintenance of infrastructure engineering.

Employing automated electrical resistivity tomography for detecting short- and long-term changes in permafrost and active-layer dynamics in the maritime Antarctic

Abstract. Repeated electrical resistivity tomography (ERT) surveys can substantially advance the understanding of spatial and temporal freeze–thaw dynamics in remote regions, such as Antarctica, where the evolution of permafrost has been poorly investigated. To enable time-lapse ERT surveys in Antarctica, an automated ERT (A-ERT) system is required, as regular site visits are not feasible. In this context, we developed a robust A-ERT prototype and installed it at the Crater Lake CALM-S site on Deception Island, Antarctica, to collect quasi-continuous ERT measurements. We developed an automated data processing workflow to efficiently filter and invert the A-ERT datasets and extract the key information required for a detailed investigation of permafrost and active-layer dynamics. In this paper, we report on the results of two complete year-round A-ERT datasets collected in 2010 and 2019 at the Crater Lake CALM-S site and compare them with available climate and borehole data. The A-ERT profile has a length of 9.5 m with an electrode spacing of 0.5 m, enabling a maximum investigation depth of approximately 2 m. Our detailed investigation of the A-ERT data and inverted results shows that the A-ERT system can detect the active-layer freezing and thawing events with high temporal resolution. The resistivity of the permafrost zone in 2019 is very similar to the values found in 2010, suggesting the stability of the permafrost over almost 1 decade at this site. The evolution of thaw depth exhibits a similar pattern in both years, with the active-layer thickness fluctuating between 0.20–0.35 m. However, a slight thinning of the active layer is evident in early 2019, compared to the equivalent period in 2010. These findings show that A-ERT datasets, combined with the new processing workflow that we developed, are an effective tool for studying permafrost and active-layer dynamics with very high resolution and minimal environmental disturbance. The ability of the A-ERT setup to monitor the spatiotemporal progression of thaw depth in two dimensions, and potentially in three dimensions, and to detect brief surficial refreezing and thawing of the active layer reveals the significance of the automatic ERT monitoring system to record continuous resistivity changes. An A-ERT monitoring setup with a longer profile length can investigate greater depths, offering effective monitoring at sites where boreholes are costly and invasive techniques are unsuitable. This shows that the A-ERT setup described in this paper can be a significant addition to the Global Terrestrial Network for Permafrost (GTN-P) and the Circumpolar Active Layer Monitoring (CALM) networks to further investigate the impact of fast-changing climate and extreme meteorological events on the upper soil horizons and to work towards establishing an early warning system for the consequences of climate change.

Spatial Distribution of Thaw Depth in Palsas Estimated From Optical Unoccupied Aerial Systems Data

ABSTRACTMaximum seasonal thaw depth, referred to as active layer thickness (ALT), is one of the key parameters used to monitor permafrost conditions. ALT maps based on interpolation of point measurements or derived from coarse or moderate spatial resolution satellite data often hide small‐scale spatial variations in thaw depth resulting from differences in surface characteristics and microtopography. To model and predict changes in hydrological and biogeochemical processes in permafrost areas accurately, high‐resolution remote sensing‐based estimations of ALT are needed. Therefore, we applied random forest (RF) regression on a set of topographical and spectral vegetation indices derived from optical unoccupied aerial systems data, Landsat 8 land surface temperature (LST) data, and field measurements to estimate thaw depths in palsas at three mires in north‐west Finland. We also analyzed differences in thaw depths between mires located at different elevations, between dome and plateau‐shaped palsas, and between different vegetation and surface cover classes. The RF models resulted in root mean square errors from 2.4 to 5.7 cm between predicted and observed thaw depths and the R2 values of 0.57–0.96. Height from the surrounding fen surface and LST were the most important variables in thaw depth models, although high‐accuracy results were also achieved without LST. The mean thaw depths did not differ between the sites with lowest and highest elevation, whereas the thaw depths were significantly deeper in dome‐shaped palsas compared to plateaus. The thaw depths were significantly different between vegetation cover classes only on plateau‐shaped palsas. The results indicate the high impact of the topography on the palsa thaw depth, thus highlighting the importance of accurate elevation models in spatial modeling of palsa ALT. The methodology presented in this study can be applied to other permafrost regions where field measurements of ALT are accompanied with high‐resolution topographical and multispectral data.

Summer heat wave in 2022 led to rapid warming of permafrost in the central Qinghai-Tibet Plateau

Extreme events with increasing frequency and intensity are significantly affecting the permafrost environment. Analysis using the ERA5-Land reanalysis data revealed that the permafrost region of the central Qinghai-Tibet Plateau (QTP) experienced the summer heat wave in 2022. Four active layer sites experienced maximum active layer thicknesses (ALT) in 2022 (mean: 207.7 cm), which was 20% higher than the mean ALT during 2000–2021 (mean: 175.9 cm). The mean annual ground temperature (MAGT) observed in 2022 was also the highest, exceeding the average of the previous years by 10%. The contribution fraction of heat wave to the seasonal thaw depth of active layer was quantified using Stefan model with ranging from 6.6% to 13.6%, and the maximum contribution fraction occurs in 2022. These findings are helpful to better understand the impact processes of extreme events on the active layer and permafrost.

Retrieval of spectral slope of chromophoric dissolved organic matter (S275–295) in Laptev Sea

Study regionLaptev Sea Study focusThe absorption slopes of colored dissolved organic matter (CDOM) in the spectral range of 275–295 nm (S275–295) is a reliable parameter of the source and transformation of CDOM and dissolved organic carbon (DOC) in the estuarine environment. Studying S275–295 in coastal areas can provide important information about CDOM and DOC. This study proposed a new multilayer backpropagation neural network (MBPNN) based on the relationship between S275–295 and aCDOM(443) (absorption of CDOM at 443 nm) as a customization function to invert S275–295. The model accurately estimated S275–295 with a MAPE and RMSE of 6.12 % and 0.0012 nm−1, respectively, and revealed the spatiotemporal distribution of S275–295 in the Laptev Sea between 2002 and 2022 (July to September). The effects of influencing factors on temporal and spatial variations of S275–295 were analyzed. New hydrological insights for the regionThe MBPNN model with a customization function has good performance to invert S275–295 in Laptev Sea. The S275–295 in the Laptev Sea ranged from 0.014 to 0.022 nm−1. S275–295 increased gradually from coastal waters to the open sea. Inter-annual S275–295 fluctuated, but no significant trend was observed during the study period (2002–2022). S275–295 was negatively correlated with river discharge (r=-0.41), permafrost thaw depth (r=-0.42), ice extent (r=-0.55) and Normalized Difference Vegetation Index (r=-0.46) but positively correlated with salinity (r=0.86) and wind speed (r=0.46).

High Arctic Vegetation Communities With a Thick Moss Layer Slow Active Layer Thaw

AbstractSvalbards permafrost is thawing as a direct consequence of climate change. In the Low Arctic, vegetation has been shown to slow down and reduce the active layer thaw, yet it is unknown whether this also applies to High Arctic regions like Svalbard where vegetation is smaller, sparser, and thus likely less able to insulate the soil. Therefore, it remains unknown which components of High Arctic vegetation impact active layer thaw and at which temporal scale this insulation could be effective. Such knowledge is necessary to predict and understand future changes in active layer in a changing Arctic. In this study we used frost tubes placed in study grids located in Svalbard with known vegetation composition, to monitor the progression of active layer thaw and analyze the relationship between vegetation composition, vegetation structure and snow conditions, and active layer thaw early in summer. We found that moss thickness, shrub and forb height, and vascular vegetation cover delayed soil thaw immediately after snow melt. These insulating effects attenuated as thaw progressed, until no effect on thaw depth was present after 8 weeks. High Arctic mosses are expected to decline due to climate change, which could lead to a loss in insulating capacity, potentially accelerating early summer active layer thaw. This may have important repercussions for a wide range of ecosystem functions such as plant phenology and decomposition processes.

Effects of Frozen Layer on Composite Erosion of Snowmelt and Rainfall in the Typical Black Soil of Northeast China

Composite erosion caused by snowmelt and rainfall causes considerable soil loss during spring thawing. However, research on the impact of frozen soil layers (FSL) on composite erosion is lacking. Therefore, indoor simulation experiments were conducted on soil conditions of 0 cm (unfrozen soil, FSLUN) and 3 cm thawing depths to explore the influence of FSL on composite erosion in the black soil region of Northeast China. Three snowmelt runoff (SR) discharges (0.34 L min−1, 0.5 L min−1, and 0.67 L min−1), three rainfall (RF) intensities (80 mm h−1, 120 mm h−1, and 160 mm h−1), and three snowmelt–rainfall interactions (SRI; 0.34 L min−1–80 mm h−1, 0.5 L min−1–120 mm h−1, and 0.67 L min−1–160 mm h−1) were used in this study. The results indicate that FSL advanced the initial erosion times of SR, RF, and SRI by 42.06%, 43.33%, and 45.83%, respectively. FSL increased the soil erosion rate (SER) of SRI by 1.2 (1.0–1.6) times that of unfrozen soil, which was smaller than that of SR (16.3, 5.6–25.0) and RF (1.7, 1.6–1.9), indicating that the interaction had an inhibitory effect on the increase in water erosion in the frozen layer. Under FSL and FSLUN conditions, RF erosion was 1.5–4.1 times and 14.5–24.3 times greater than SR erosion. The SRI erosion was not a simple linear superposition of multiple types of single-phase erosion; it had a significant nonlinear superposition amplification effect (SAE), with SAE of ~100% and ~300% under frozen and unfrozen soil conditions. Flow velocity (0.11 < R2 < 0.68), stream power (0.28 < R2 < 0.88), and energy consumption (0.21 < R2 < 0.87) exhibited significant (p < 0.05) linear relationships with SER in both FSL and FSLUN. The research results deepen our understanding of the composite erosion process during the spring thawing period in the black soil region of Northeast China and provide a basis for the prevention and control of soil erosion in the region.

The Impact of Catastrophic Forest Fires of 2021 on the Light Soils in Central Yakutia

This paper presents the results of studying changes in the main parameters and properties of soils in larch and pine forests growing on sandy soils of the Lena-Vilyui interfluve of Central Yakutia, where catastrophic forest fires occurred in 2021. According to the remote monitoring information system of Rosleskhoz, in 2021, almost 8.5 million hectares of forests burned in Yakutia, which is considered as one of the largest forest fires in Russia and in the world in that year. After the fire passes through the forest floor, the content of organic matter decreases as a result of combustion processes. The acidity of the soil changes towards its alkalization due to the entry of combustion products. Changes in soil profiles occur; turbation processes begin more intensively, which in turn change the natural distribution of soil indicator values such as the organic carbon content, the pH, and the number of exchangeable bases. Due to the sharp increase in heat supply after a fire, the depth of seasonal thawing in the soils of burnt larch forests increases by a quarter and by twofold in pine forests. With the beginning of the thawing of the seasonally frozen layer, all the soils experience waterlogging, and ground water occurs above the permafrost.

Hydrological Regime of Rivers in the Periglacial Zone of the East European Plain in the Late MIS 2

At the end of the Pleniglacial and the first half of the Late Glacial period, approximately between 18 and 14 ka BP, rivers of the central and southern parts of the East European Plain had channels up to 10 times as large as the present day channels of the same rivers. These ancient channels, called large meandering palaeochannels, are widespread in river floodplains and low terraces. The hydrological regime of these large rivers is of great interest in terms of the palaeoclimatology of the late Marine Isotope Stage 2 (MIS 2). In this study, we aimed at quantitative estimation of maximum flood discharges of rivers in the Dnepr, Don and Volga basins in the late MIS 2. To approach this, we used massive measurements of the morphometric characteristics of large palaeochannels on topographic maps and remote sensing data—palaeochannel width, meander wavelength and their relationships with river flow parameters. The runoff depth of the maximum flood, which corresponds to the maximum depth of daily snow thaw during the snowmelt period, was obtained for unit basins with an area of <1000 km2. The mean value for the southern megaslope of the East European Plain was 44.2 mm/day (6 times the modern value), with 46 mm/day for the Volga River (5.5 times), 45 mm/day (6.3 times) for the Don River and 39 mm/day (8 times the modern value) for the Dnepr River basins. In general, the Dnepr basin was drier than the Don and Volga basins, which corresponds well to the modern distribution of humidity. At the same time, the westernmost part of the Dnepr River basin was relatively wet in the past, and the decrease in humidity from the past to the modern situation was greater there than in the eastern and central regions. The obtained results contradict the prevailing ideas, based mainly on climatic modeling and palynological data, that the climate of Europe was cold and dry during MIS 2. The reason is that palaeoclimatic reconstructions were made predominantly for the LGM epoch (23–20 ka BP). On the East European Plain, the interval 18–14 ka BP is rather poorly studied. Our results of paleoclimatological and palaeohydrological reconstructions showed that the Late Pleniglacial and the first half of the Late Glacial period was characterized by a dramatic increase in precipitation and river discharge relative to the present day.

Virus ecology and 7-year temporal dynamics across a permafrost thaw gradient.

Soil microorganisms are pivotal in the global carbon cycle, but the viruses that affect them and their impact on ecosystems are less understood. In this study, we explored the diversity, dynamics, and ecology of soil viruses through 379 metagenomes collected annually from 2010 to 2017. These samples spanned the seasonally thawed active layer of a permafrost thaw gradient, which included palsa, bog, and fen habitats. We identified 5051 virus operational taxonomic units (vOTUs), doubling the known viruses for this site. These vOTUs were largely ephemeral within habitats, suggesting a turnover at the vOTU level from year to year. While the diversity varied by thaw stage and depth-related patterns were specific to each habitat, the virus communities did not significantly change over time. The abundance ratios of virus to host at the phylum level did not show consistent trends across the thaw gradient, depth, or time. To assess potential ecosystem impacts, we predicted hosts in silico and found viruses linked to microbial lineages involved in the carbon cycle, such as methanotrophy and methanogenesis. This included the identification of viruses of Candidatus Methanoflorens, a significant global methane contributor. We also detected a variety of potential auxiliary metabolic genes, including 24 carbon-degrading glycoside hydrolases, six of which are uniquely terrestrial. In conclusion, these long-term observations enhance our understanding of soil viruses in the context of climate-relevant processes and provide opportunities to explore their role in terrestrial carbon cycling.

Influence of tundra fire severity on vegetation recovery in the Northwest Territories

Anthropogenic climate change has driven an increase in the frequency, size, and severity of fires at high latitudes. Recent research shows that increasing fire severity in the subarctic is altering the trajectories of forest succession, but to date, research on the effect of fire severity on tundra succession has been limited. In this study, we investigated short-term recovery of shrub tundra communities following fire in the Tuktoyaktuk Coastal Plain and Anderson River Plain ecoregions of the Northwest Territories. To understand the effects of fire severity, we documented vegetation and permafrost recovery within moderately burned, severely burned, and unburned portions of six tundra fires that burned in 2012. We found that vegetation structure at moderately and severely burnt sites recovered rapidly toward pre-fire levels, but that differences in community composition, characterized by a decrease in shrub and lichen cover as well as an increase in abundance of ruderals and graminoids, persisted at severely burned sites. The persistence of thermal changes and increased thaw depth indicate that while biotic recovery can occur promptly, severe fire may have long-term impacts on belowground conditions.

Application of the Machine Learning Method to Determine Spring Load Limits and Winter Weight Premium

Freight transportation plays a crucial role in sustaining the Canadian economy. However, heavy truck transportation also puts enormous pressure on roadway networks. Spring Load Restrictions (SLR) are implemented to minimize road damage caused by heavy traffic during the thaw-weakening season, and Winter Weight Premium (WWP) is used to reduce the impact of SLR on trucking operations by allowing higher axle loads in winter. However, existing policies apply fixed dates each year for these restrictions, regardless of the actual structural capacity of the pavement. Different methods have been proposed to improve the application of SLR and WWP; however, they rely mainly on indirect indices, such as the cumulative thawing index and cumulative freezing index, which pose challenges in their calculation. This study explores the practical implementation of machine learning models for accurately determining the start and end dates of SLR and WWP. In a novel approach, machine learning models directly derive the start and end dates of SLR and WWP from frost and thaw depths in the pavement structure which are determined by pavement temperature and moisture content. In contrast to previous studies that neglected the influence of soil moisture content on determining the start and end dates of SLR and WWP, this study examines the variation in soil moisture content to evaluate the validity of existing theories. The findings reveal a high level of agreement between the machine learning model’s estimations of frost and thaw depths and the measured values, with R2 values exceeding 0.91.

Small-scale hydrological patterns in a Siberian permafrost ecosystem affected by drainage

Abstract. Climate warming and associated accelerated permafrost thaw in the Arctic lead to a shift in landscape patterns, hydrologic conditions, and release of carbon. In this context, the lateral transport of carbon and shifts therein following thaw remain poorly understood. Crucial hydrologic factors affecting the lateral distribution of carbon include the depth of the saturated zone above the permafrost table with respect to changes in water table and thaw depth and the connectivity of water-saturated zones. Landscape conditions are expected to change in the future due to rising temperatures and polygonal or flat floodplain Arctic tundra areas in various states of degradation; hydrologic conditions will also change. This study is focused on an experimental site near Chersky, northeast Siberia, where a drainage ditch was constructed in 2004 to simulate landscape degradation features that result in drier soil conditions and channeled water flow. We compared water levels and thaw depths in the drained area (dry soil conditions) with those in an adjacent control area (wet soil conditions). We also identified the sources of water at the site via stable water isotope analysis. We found substantial spatiotemporal changes in the water conditions at the drained site: (i) lower water tables resulting in drier soil conditions, (ii) quicker water flow through drier areas, (iii) larger saturation zones in wetter areas, and (iv) a higher proportion of permafrost meltwater in the liquid phase towards the end of the growing season. These findings suggest decreased lateral connectivity throughout the drained area. Shifts in hydraulic connectivity in combination with a shift in vegetation abundance and water sources may impact carbon sources and sinks as well as transport pathways. Identifying lateral transport patterns in areas with degrading permafrost is therefore crucial.

Mitigation of shady-sunny slopes effect on subgrade by photovoltaic sheltered boards in permafrost regions

With the great demand of global carbon reduction, a novel method, such as photovoltaic shelter board (PSB), is proposed to mitigate the shady-sunny slope effects in permafrost. The idea of PSB is an extension of traditional shelter board, which can potentially eliminate the shady-sunny slope effect in theory. However, its quantitative performance is still unclear due to limited application and research. To overcome this gap and explore the application possibilities of PSB in cold regions, this paper introduces a novel photovoltaic sheltered board subgrade and numerically investigates its effectiveness in mitigating the shady-sunny slope effect. Initially, a heat transfer model incorporating solar radiation and air convection was developed and validated with field-monitored ground temperature data. Analyses based on this model compare the thermal imbalance effects on exposed subgrade, traditional insulation boards subgrade, and the novel photovoltaic sheltered board subgrade. Results indicate that the photovoltaic sheltered board exhibits superior mitigation effects to traditional insulation boards, primarily due to enhanced heat dissipation by air convection in the suspension region. In the study area, the photovoltaic sheltered board significantly lowers sunny slope temperatures by over 3 ℃ on average and thaw depth by more than 1m compared to exposed subgrade. The photovoltaic sheltered board’s suspension height should not be less than 5.3cm to mitigate the sunny-shady slope effect effectively in this region. In summary, this study provides a reference for mitigating the shady-sunny slope effects and reducing carbon release in permafrost subgrade engineering.

Использование экзотермической реакции гашения извести для локального оттаивания сезонномерзлых грунтов

The the results of scientific and experimental work are described, the purpose of which was to determine the depth of thawing of seasonally frozen soils using the lime extinguishing reaction as a source of heat. The analysis of meteorological, agrometeorological conditions typical for Uralsk was carried out. The method, which provides an opportunity to use the heat released in the interaction of calcium oxide with water, was developed. To implement this method, a heat-insulating structure is designed and manufactured, which allows to accumulate and direct the accumulated heat through the heating system «from top to bottom». It was found that the use of the described method makes it possible to achieve a thawing depth of the soil up to 56 cm. At the time of scientific-experimental work, this thawing depth indicator exceeded the actual depth of soil freezing

The main results of monitoring the power of the active layer at CALM sites of the Nadymsky object

Monitoring of the thickness of the active layer within the lake-marsh type of terrain in the northern taiga was carried out at three sites organized in 1997, 2013 and 2022. In these areas, two types of tracts are distinguished: frozen peat bogs and swampy runoff hollows with a lowered roof of permafrost (the cross-section of the sites is the same type, the only difference is in the thickness of the peat). The work methodology complied with the unified protocol of the international CALM program. Additionally, the surface settlement was assessed (based on leveling from a local benchmark), geophysical studies were carried out and the temperature of the active layer rocks was measured at different gullies. In swampy runoff hollows, hollows with open water and on specific mineral spots within peat bogs, the depth of the permafrost roof is 3–10 m. At the boundaries of peat bogs and in swampy runoff hollows, the thawing depth exceeds 2 m, and on peat bogs it varies from 0.8 to 1.6 m depending on the thickness of the organic layer and the condition of the ground cover. On peatlands with an organic layer more than 1 m thick and a continuous ground cover, the depth of the seasonal thawing layer in some places does not exceed 0.4 m. These peatlands respond poorly to climate change. The depth of the permafrost roof within thin peat bogs (less than 0.5 m of peat) with oppressed vegetation cover is currently more than 2 m, marking the beginning of the replacement of the seasonally thawed layer with seasonally frozen and the formation of areas with a lowered permafrost roof. Monitoring of soil temperatures in such areas has showed that a random combination of climatic factors in individual years can lead to short-term (two years) new formation of permafrost or the merging of seasonal permafrost with permafrost. Thus, the formation of non-merging permafrost is of a reciprocating nature.