Depth Of Soil Freezing Research Articles

Mapping Frozen Ground in the Qilian Mountains in 2004–2019 Using Google Earth Engine Cloud Computing

The permafrost in the Qilian Mountains (QLMs), the northeastern margin of the Qinghai–Tibet Plateau, changed dramatically in the context of climate warming and increasing anthropogenic activities, which poses significant influences on the stability of the ecosystem, water resources, and greenhouse gas cycles. Yet, the characteristics of the frozen ground in the QLMs are largely unclear regarding the spatial distribution of active layer thickness (ALT), the maximum frozen soil depth (MFSD), and the temperature at the top of the permafrost or the bottom of the MFSD (TTOP). In this study, we simulated the dynamics of the ALT, TTOP, and MFSD in the QLMs in 2004–2019 in the Google Earth Engine (GEE) platform. The widely-adopted Stefan Equation and TTOP model were modified to integrate with the moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) in GEE. The N-factors, the ratio of near-surface air to ground surface freezing and thawing indices, were assigned to the freezing and thawing indices derived with MODIS LST in considerations of the fractional vegetation cover derived from MODIS normalized difference vegetation index (NDVI). The results showed that the GEE platform and remote sensing imagery stored in Google cloud could be quickly and effectively applied to obtain the spatial and temporal variation of permafrost distribution. The area with TTOP < 0 °C is 8.4 × 104 km2 (excluding glaciers and lakes) and accounts for 46.6% of the whole QLMs, the regional mean ALT is 2.43 ± 0.44 m, while the regional mean MFSD is 2.54 ± 0.45 m. The TTOP and ALT increase with the decrease of elevation from the sources of the sub-watersheds to middle and lower reaches. There is a strong correlation between TTOP and elevation (slope = −1.76 °C km−1, p < 0.001). During 2004–2019, the area of permafrost decreased by 20% at an average rate of 0.074 × 104 km2·yr−1. The regional mean MFSD decreased by 0.1 m at a rate of 0.63 cm·yr−1, while the regional mean ALT showed an exception of a decreasing trend from 2.61 ± 0.45 m during 2004–2005 to 2.49 ± 0.4 m during 2011–2015. Permafrost loss in the QLMs in 2004–2019 was accelerated in comparison with that in the past several decades. Compared with published permafrost maps, this study shows better calculation results of frozen ground in the QLMs.

Опыт применения поверхностных фундаментов для каркасного здания в окрестностях Cанкт-Петербурга

The article presents the experience of constructing buildings on surface foundations in winter season. Within the frames of the investigation, there were evaluated temperatures in the base composed of heaving soils, as well as foundation displacements during the winter period. There have been were performed calculations of temperature fields and soil heaving deformation using the Termoground program. It is shown that despite the relatively big depth of the base soil freezing, the maximum displacements of the foundations did not exceed 7 mm, which is quite acceptable for a frame building.

PREVALENCE OF ASCARIASIS IN THE CHUVASH REPUBLIC

The analysis of ascariasis prevalence in the Chuvash Republic for the period 1997-2017 was carried out depending on natural and anthropogenic environmental factors. As a result of multiple regression analysis including 61 factors integrated into the matrix for regression analysis, 19 factors were selected which were statistically significantly associated with the incidence of ascariasis depending on the administrative-territorial structure of the Republic. The chosen factors are divided into six groups: group 1 – factors reflecting the characteristics of water balance and the distribution of water masses in the area: (a) average annual flow (coefficient = 0.761), determining the amount of water flowing along river beds per year; b) the number of drilled wells (coefficient = 0.5133); c) the average snow cover height (coefficient = 0.2940); d) 4) the average amount of precipitation for the winter period (coefficient = 0.0073); e) the average number of sources whoch do not conform to sanitary standards and regulations (coefficient = -0.3309); f) drainage network density in km per km2 (coefficient = –0.0152), i.e. water balance and distribution of water masses in the territory of the region determine the direct impact on the incidence of ascariasis; group 2 – factors created by agricultural human activities related to soil: (a) the average annual number of poultry per 100 hectares of crops (coefficient = 0.2265); b) the specific weight of agricultural livestock areas in the entire area of agricultural land,% (coefficient = 0.2537); c) sheep stock per 100 hectares of agricultural land (coefficient = 0.1838), as it is known, livestock objects maintain viable helminth eggs for a long time; group 3 – ecological-climatic factors: a) fluctuations within the limits of baseline radiation background (coefficient = -0.2537); b) average year-round temperature (coefficient = –0,1103); c) depth of soil freezing (coefficient = –0.0412) – this group of factors is a deterrent in the spread of ascariasis because it directly affects to slow down the maturation of eggs and contributes to the early loss of vitality. As a result of cartography, a high incidence of ascariasis is noted in areas with prevalence of typical gray forest soils in combination with light gray and dark gray forest soils, in areas with gray cespitose- cryptopodzol soils. It is Krasnochetaisky region – 171,17±108,36 cases per 100 thousand population, Alikovsky region – 118,5±74.4 and Shumerlinsky region – 70,5±47,8. The minimum morbidity is in Yalchiksky region – 12,10±9,14. Conclusions: 1) the incidence of ascariasis in the territory of the Chuvash Republic is of a mosaic character. The incidence of ascariasis prevails in administrative-territorial regions located in the western part of the Chuvash Republic; 2) it is statistically proved that such a hydro-geological feature of the territory as annual runoff, including spring flooding, has a significant negative impact on morbidity; 3) such environmental and climatic factors as annual average temperature and the depth of soil freezing, have a deterrent effect on the incidence of ascariasis.

Different Responses of Vegetation to Frozen Ground Degradation in the Source Region of the Yellow River from 1980 to 2018

Frozen ground degradation under a warming climate profoundly influences the growth of alpine vegetation in the source region of the Qinghai-Tibet Plateau. This study investigated spatiotemporal variations in the frozen ground distribution, the active layer thickness (ALT) of permafrost (PF) soil and the soil freeze depth (SFD) in seasonally frozen soil from 1980 to 2018 using the temperature at the top of permafrost (TTOP) model and Stefan equation. We compared the effects of these variations on vegetation growth among different frozen ground types and vegetation types in the source region of the Yellow River (SRYR). The results showed that approximately half of the PF area (20.37% of the SRYR) was projected to degrade into seasonally frozen ground (SFG) during the past four decades; furthermore, the areal average ALT increased by 3.47 cm/yr, and the areal average SFD decreased by 0.93 cm/yr from 1980 to 2018. Accordingly, the growing season Normalized Difference Vegetation Index (NDVI) presented an increasing trend of 0.002/10yr, and the increase rate and proportion of areas with NDVI increase were largest in the transition zone where PF degraded to SFG (the PF to SFG zone). A correlation analysis indicated that variations in ALT and SFD in the SRYR were significantly correlated with increases of NDVI in the growing season. However, a rapid decrease in SFD (< −1.4 cm/10yr) could have reduced the soil moisture and, thus, decreased the NDVI. The NDVI for most vegetation types exhibited a significant positive correlation with ALT and a negative correlation with SFD. However, the steppe NDVI exhibited a significant negative correlation with the SFD in the PF to SFG zone but a positive correlation in the SFG zone, which was mainly limited by water condition because of different change rates of the SFD.

Soil erosion: An important indicator for the assessment of land degradation neutrality in Russia

This review of soil erosion (SE) studies in Russia focuses on two main tasks: (i) ensuring the completeness and reliability of SE data in Russia, a large country (17.1 million km2) with a variety of natural and socio-economic causes of land degradation, (ii) assessing the possibility of including a SE indicator among the indicators of land degradation neutrality (LDN). A wide range of statistical, remote sensing, mathematical modeling data, the results of scientific and field studies obtained at different levels were analyzed. It is asserted that in Russia the total area of eroded lands and those under erosion risk occupy more than 50% of all agricultural lands, whereas soil fertility of croplands decreased in Soviet time (from 1950s to 1980s) by 30–60% only due to water erosion. However, recent scientific studies indicate a decrease in erosion rate and in the area of eroded land during the last 30–40 years as a result of abandonment of arable land and subsequent overgrown with natural vegetation. The climate change resulting in decrease of the depth of soil freezing, flow of spring runoff also adds to the decrease of soil erosion. The SE indicator was suggested as an important complement to three global LDN indicators. At national and subnational level, it can be interpreted through such indices as “Rate of soil loss” (ton ha-1 yr-1) and “Total soil loss” (1000 tons, in certain area during selected time period). At local level the set of indices can be wider and site-specific, including those obtained through remote sensing data by using the classifier of thematic applications of remote sensing technologies; the example was tested at the local site.

Changes in the Seasonally Frozen Ground Over the Eastern Qinghai-Tibet Plateau in the Past 60 Years

The Qinghai-Tibet Plateau (QTP) has the largest extent of high altitude permafrost at the middle and low latitudes in northern hemisphere and is surrounded by dozens of seasonally frozen ground. Rising air temperatures have resulted in frozen ground degradation over QTP since the last century. Based on the daily frozen soil depth, annual mean daily minimum air temperatures and annual mean air temperatures obtained from 19in-situobservations over QTP, the changes in the thickness, temporal and spatial distributions of frozen ground, as well as the associated attributions, are analyzed for the period of 1960-2019. The results show that the maximum depth of frost penetration, the beginning time of soil freezing and the ending time of soil thawing have changed considerably. On average, the maximum depth of frost penetration (MDFP) has reduced by 0.14 similar to 1.71 m at most stations. The annual frozen period has decreased by about 40 days. The changes in seasonal freezing of soils appear to be attributed to the rising of minimum air temperatures in winter, especially at the higher elevations range from 4500 to 5000 m.

Variability of soil freeze depth in association with climate change from 1901 to 2016 in the upper Brahmaputra River Basin, Tibetan Plateau

Soil freeze depth (SFD) is necessary to evaluate the variations in water resource balances, surface energy exchanges, and biogeochemical cycles in the frozen ground regions, while the variability of regional SFD under climate changes remains unknown, mainly due to the insufficiency of effective observations. Significant changes of frozen ground related to water resources and the eco-environment have occurred in the Upper Brahmaputra River Basin (UBRB) (also known as the Yarlung Zangbo River) on the southern Tibetan Plateau, which is a key area where SFD monitoring is scarce. In this study, we adopted the Stefan equation to simulate the regional maximum SFD over the UBRB from 1901 to 2016 with monthly near-surface air temperatures from the University of East Anglia Climatic Research Unit (UEA-CRU) and the University of Delaware (UDEL). Observations from 11 national meteorological stations over the UBRB and 6 nearby were used to calibrate relevant parameters and evaluate the simulations. Studies showed that maximum SFD is positively correlated with air freezing index (AFI), ground surface freezing index (GFI), and snow depth (SD) and is negatively correlated with air thawing index (ATI), ground surface thawing index (GTI), mean annual air temperature (MAAT), and mean annual ground surface temperature (MAGST). Approximately 97.94% and 96.21% of the UBRB were covered with the frozen ground as simulated with the UEA-CRU and the UDEL, respectively. The maximum SFD calculated with the UEA-CRU and the UDEL decreased respectively by about 0.31 m and 0.15 m over the past 116 years. Simulations with both datasets demonstrated that no significant changes of SFD occurred in the past four 30-year periods (i.e., 1901–1930, 1931–1960, 1961–1990, and 1991–2016), while the maximum SFD calculated with the UEA-CRU was smaller than that with the UDEL. All of these features demonstrated a warming trend of frozen ground from 1901 to 2016 in the UBRB.

Remote sensing spatiotemporal patterns of frozen soil and the environmental controls over the Tibetan Plateau during 2002–2016

The changing climate is affecting the frozen soil at an unprecedented rate across the Northern Hemisphere. However, due to sparse ground measurements, the changes of frozen soil and the environmental controls over the vast cryosphere are still unclear, such as in the Tibetan Plateau (TP). In this study, a process-based model solely driven by satellite remote sensing data is employed to investigate the spatiotemporal changes of seasonally frozen ground and permafrost over the entire TP (~3 million km2) during 2002–2016 at a spatial resolution of 1 km. Comprehensive validations against in situ observations of frozen ground types, mean annual ground temperature, active layer thickness, soil temperature, and frozen depth at 608 boreholes and 109 meteorological stations demonstrate an overall satisfactory performance of the model in reproducing the spatial pattern and temporal evolution of the frozen soil in the region. Spatially, land surface temperature (LST; both in-season and off-season) primarily controls the frozen ground types and frozen depth, with seasonally frozen ground and permafrost covering ~56% and ~ 37% of the plateau, respectively. The estimated spatial-averaged annual maximum soil freeze depth (SFD) is ~1.29 m, and the annual maximum active layer thickness (ALT) of permafrost is ~1.85 m. Temporally, ALT shows an overall increasing trend at an average rate of +3.17 cm yr−1, while SFD exhibits both decreasing (at ~62% areas) and increasing (at ~38% areas) trends in the region. Again, LST is found to be the dominant factor that controls the temporal changes in both SFD and ALT while precipitation (i.e., both rainfall and snowfall) plays an important (especially in more arid areas and regions near the lower limit of permafrost) but secondary role. Our results demonstrate the advantages of the satellite-based method in frozen soil simulations over large scales with complex topography and landscape and highlight the important roles of both temperature and precipitation in shaping the frozen soil patterns on the TP or other cold, dry regions.

Transpiration of Dominant Tree Species Varies in Response to Projected Changes in Climate: Implications for Composition and Water Balance of Temperate Forest Ecosystems

The climate is changing in many temperate forests with winter snowpack shrinking and an increasing frequency of growing season air temperatures exceeding long-term means. We examined the effects of these changes on growing season rates of transpiration (sap flow) in two snow removal experiments in New Hampshire and Massachusetts, USA. Snow was removed during early winter, resulting in greater depth and duration of soil freezing compared to untreated plots. We examined the dominant tree species at each site, Acer saccharum at Hubbard Brook, NH and Acer rubrum and Quercus rubra at Harvard Forest, MA. Trees responded to a smaller snowpack, but with distinct species-specific responses consistent with ecological traits. Snow removal decreased rates of sap flow per kPa vapor pressure deficit (VPD) in sugar maples in the early growing season and red maples throughout the growing season. In contrast, sap flow rates per kPa VPD increased for red oak with snow removal. Downscaled climate projections from the Coupled Model Intercomparison Project indicate increases in heat stress days at both sites by the end of the century, leading to increased rates of whole-season transpiration across all three tree species, which will be offset in red maples and increased in red oaks with a smaller snowpack and increased frequency of heat stress days. Results of this study demonstrate that the combined effects of changes in climate during the growing season and winter will impact transpiration differently among tree species, with implications for forest water balance and tree species composition in the northeastern USA

ВЛИЯНИЕ ИЗМЕНЕНИЯ КЛИМАТА НА ЮГЕ РОССИИ НА СТОК ТАЛЫХ ВОД

Purpose: generalization and analysis of long-term observations for climatic indicators changes and the surface melt water runoff value and study of their effect on soil erosion using the example of Rostov region. Research objectives: to analyze global and regional climate changes in Rostov region from 1936 to 2019, to determine the patterns of the climate change impact on surface runoff and soil erosion (based on long-term field observations from 1970 to 2020). Methods: observations for surface runoff were carried out at runoff sites according to generally accepted methods; the methods of mathematical analysis and statistics were used to summarize and analyze the data obtained. Results. The analysis showed that for the period from 1936 to 2019, the average annual temperature in Rostov region increased by an average of 1.9 °С, the amount of precipitation increased by an average of 148 mm, but the unevenness of their precipitation by months increased, and only in August there is a regular decrease in precipitation at all observation points. This was reflected in the depth of soil freezing, which averaged 47.5 cm from 1970 to 1990, and from 2010 to 2020 decreased to 19 cm, i. e., almost 2.5 times. From 1970 to 1990, the water reserve in the snow before snowmelt was 53.6 mm, from 1991 to 2009 – 43.4 mm, from 2010 to 2020 – 33.5 mm, i. e., there was a decrease in comparison with the first period by 1.6 times. Conclusions. Observation for the melt water runoff for the above period showed that the runoff layer decreased from 19.0 to 4.2 mm, and the probability of its formation is 1 time in 3 years on loose arable land, and 2 times in 3 years on compacted land. In accordance with this, the value of soil washout in the period 1970–1990 amounted to 8.9 t/ha, and in the last decade, 2 times less – 4.2 t/ha. All these data should be taken into account when planning the system of soil protection measures.

Soil freeze depth variability across Eurasia during 1850–2100

Soil freeze depth (SFD) is an important indicator of cryospheric and climate change. Changes in SFD have important effects on hydrology, the energy balance, carbon exchange, and ecosystem diversity. However, quantifying and predicting SFD at large scales remains a challenge due to sparse long-term observations. This study employs the Stefan solution combined with 16 of the coupled model inter-comparison project phase 5 (CMIP5) models over the historical period (1850–2005) and three representative concentration pathways (RCP 2.6, 4.5, and 8.5) for 2006–2100, the Climatic Research Unit dataset (1901–2013), and hundreds of soil temperature, air temperature, precipitation, and snow depth sites to analyze the spatiotemporal variability of SFD in Eurasia under historical and projected climate change. During 1850–2005, a statistically significant SFD decrease of 0.49 ± 0.04 cm/decade is observed. Spatially, the biggest decreases are generally in Siberia and on the Tibetan Plateau. There is a projected decrease in 2006–2100 SFD of 4.58 ± 0.26, 1.85 ± 0.21, and 0.45 ± 0.18 cm/decade for RCP 8.5, 4.5, 2.6, respectively. These variations in SFD provide key insights into spatiotemporal changes in climate, and facilitate improved understanding of variation in frozen ground across Eurasia.

Changes in the depths of seasonal freezing and thawing and their effects on vegetation in the Three-River Headwater Region of the Tibetan Plateau

Frozen ground degradation plays an important role in vegetation growth and activity in high-altitude cold regions. This study estimated the spatiotemporal variations in the active layer thickness (ALT) of the permafrost region and the soil freeze depth (SFD) in the seasonally frozen ground region across the Three Rivers Source Region (TRSR) from 1980 to 2014 using the Stefan equation, and differentiated the effects of these variations on alpine vegetation in these two regions. The results showed that the average ALT from 1980 to 2014 increased by 23.01 cm/10a, while the average SFD decreased by 3.41 cm/10a, and both changed intensively in the transitional zone between the seasonally frozen ground and permafrost. From 1982–2014, the increase in the normalized difference vegetation index (NDVI) and the advancement of the start of the vegetation growing season (SOS) in the seasonally frozen ground region (0.0078/10a, 1.83d/10a) were greater than those in the permafrost region (0.0057/10a, 0.39d/10a). The results of the correlation analysis indicated that increases in the ALT and decreases in the SFD in the TRSR could lead to increases in the NDVI and advancement of the SOS. Surface soil moisture played a critical role in vegetation growth in association with the increasing ALT and decreasing SFD. The NDVI for all vegetation types in the TRSR except for alpine vegetation showed an increasing trend that was significantly related to the SFD and ALT. During the study period, the general frozen ground conditions were favorable to vegetation growth, while the average contributions of ALT and SFD to the interannual variation in the NDVI were greater than that of precipitation but less than that of temperature.

Effect of thaws on snow cover and soil freezing under the contemporary climate change

Thaw and liquid precipitation retard cooling of snow cover and soil surface and so may be a factor of heating. This slows down the soil freezing due to more active freezing of the wet snow, and, thus, promotes cooling and re-cooling of the soil. However, there are a number of factors which intensify the soil freezing after thaw. With thaw, the thickness of the snow cover decreases, and its density increases. In addition, after freezing wet snow improves the contact between the ice crystals, which increases the hardness and thermal conductivity of the snow. As a result, after the thaw, the thermal protection ability of the snow decreases, and this can accelerate freezing of the soil. The dynamics of snow accumulation in Russia is considered in the paper. Using data obtained in the Western Svalbard, we demonstrate the increase in the number of thaws and liquid precipitation and influence of them on the snow cover and soil freezing. The influence of thaw on the growth of thermal resistance of snow cover is also considered. Calculations have shown that in the absence of a thaw, the depth of soil freezing is 1.26 m. With a thaw lasting 10 days, which begins on the 40th day from the start of soil freezing, the depth of freezing is reduced down to 1.2 m without considering changes in snow cover. When taking into account changes in the thermal resistance of snow cover, the depth of soil freezing by the end of the cold period increases up to 1.32 cm. With a thaw in the mid-winter, i.e. on the 70th day, the depth of freezing decreases down to 1.22 m, that is smaller than the depth of freezing without thaw. This scenario is in accordance with changes in snow accumulation dynamics under the present-day climate, as in many areas most of the solid precipitation falls in the first half of the cold period. As a result, for a period after a thaw the smaller volume of snow will be deposited, and this will retard increasing in thermal resistance of the snow cover

Evaluating climate and water regime transformation in the European part of Russia using observation and reanalysis data for the 1945–2015 period

ABSTRACT The river runoff regime significantly changed worldwide in the end of twentieth – the beginning of twenty-first century. In the European part of Russia the current changes are manifested in different ways in various regions. The main trend that is observed for most river basins is the ‘levelling’ of annual hydrographs. The interception of melt water during occasional thaw floods has resulted in a decrease in river runoff during the spring months. Simultaneously an increase in the low water period during winter and summer occurred. Reducing in the depth of soil freezing, caused by warm winters, lead to higher groundwater replenishment. At the same time, the loss of melt water to surface retention as well as evaporation has increased. Almost in all seasons of the year the number of occasional flood peaks increases. Occasional floods are superimposed both on the rise and the decline of seasonal snowmelt flood wave, making it difficult to separate it as an independent phase of the water regime. Changes in seasonal characteristics of river runoff are the most evident in the Don and Oka basins. A significant transformation of the water regime is observed in the north-west of European Russia as well. To a lesser extent, the described patterns are typical for the northern rivers and the eastern part of the European Russia – the Kama and the Ural Basin.

The Cyclicity in the Dynamics of Different Populations of the Common Shrew

Abstract—Different populations of the Common shrew (Sorex araneus) were analyzed with regard to multiyear cycles of population fluctuations typical for the species. We presented data on long-term observations in Akademgorodok (Novosibirsk) and Rovenskoe village (Central Baraba). We also used published data on long-term observations from the European and East Siberian range of the shrew populations. This work attempts to develop a general idea on the cyclicity in multiyear population number dynamics of the Common shrew, invariant and variable in different geographical locations. The data series were analyzed using spectral analysis. The main cycles in this species are 10–15, five to seven, three to four, and two to three3 years, however the amplitude of the cycles varied by region. To maintain population cyclicity, synchronization with local rhythms similar in parameters is important: geomagnetic activity, depth of soil freezing, thickness of snow cover, and watering of the territory.

Development of a Parameterized Model to Estimate Microwave Radiation Response Depth of Frozen Soil

The sensing depth of passive microwave remote sensing is a significant factor in quantitative frozen soil studies. In this paper, a microwave radiation response depth (MRRD) was proposed to describe the source of the main signals of passive microwave remote sensing. The main goal of this research was to develop a simple and accurate parameterized model for estimating the MRRD of frozen soil. A theoretical model was introduced first to describe the emission characteristics of a three-layer case, which incorporates multiple reflections at the two boundaries. Based on radiative transfer theory, the total emission of the three layers was calculated. A sensitivity analysis was then performed to demonstrate the effects of soil properties and frequency on the MRRD based on a simulation database comprising a wide range of soil characteristics and frequencies. Sensitivity analysis indicated that soil temperature, soil texture, and frequencies are three of the primary variables affecting MRRD, and a definite empirical relationship existed between the three parameters and the MRRD. Thus, a parameterized model for estimating MRRD was developed based on the sensitivity analysis results. A controlled field experiment using a truck-mounted multi-frequency microwave radiometer (TMMR) was designed and performed to validate the emission model of the soil freeze–thaw cycle and the parameterized model of MRRD developed in this work. The results indicated that the developed parameterized model offers a relatively accurate and simple way of estimating the MRRD. The total root mean square error (RMSE) between the calculated and measured MRRD of frozen loam soil was approximately 0.5 cm for the TMMR’s four frequencies.

The Models of Permafrost for Arid and Alpine Regions

Stationary models of the thermal regime of permafrost taking into account water evaporation and ice sublimation within upper layer of soil are submitted. The results of Chinese researchers in mountainous Tibet and theoretical approach of Russian scientists for Northern Tien Shan are discussed. The thickness of the frozen rocks may reach an unexpectedly very large depth up to 100 m and more. Traditional stationary model of permafrost (Model Problem #0) was examined. The authors of the paper theoretically based the thermal regime of formation permafrost of cryolithozone in the highlands (two-stratum Model Problem #1). The new mechanism of formation of the thermal regime caused evaporation and sublimation processes in dispersed rocks in conditions of arid (high land) climate are suggested. Evaporation when filtering moisture in the upper soil layers is like heat sink. Then this process becomes the primary for the temperature field variations inside coarse clastic sediments. Additionally ice sublimation can increase heat dissipation in dispersed rocks. Three-stratum Model Problem #2 with a certain subsurface volumetric layer under frost desiccation was introduced. This soil layer being between the upper one of evaporation and the deep one of permafrost may generate a significant heat effect on the depth of freezing. Temperature minimum of the thermal system is formed in subsurface layer and cause heat sink into frozen soil depth. Numerical evolutions for the proposed models correspond to experimental data on the intensity of evaporation and sublimation for the surface and subsurface layers of permafrost, as well as the processes of cooling and freezing in dispersed rocks. This research will be in demand in engineering Cryolithology and Glaciology.

On evaluation of depth of soil freezing based on Smos satellite data

The results of a comparative analysis of the brightness temperatures determined from the SMOS satellite and the corresponding depths of soil freezing, measured at weather stations located at the test sites of the Kulunda Plain, are presented. Based on the daily satellite measurement of brightness temperature, the effect of soil freezing on the microwave radiation of the underlying surface was studied. A theoretical calculation of the dependence of soil brightness temperature on the depth of freezing is performed with the model of microwave radiation of a plane-layered inhomogeneous non-isothermal medium. The real parameters of the Kulunda plain soil as well as the climatic characteristics of the sites under study, obtained from the weather stations for the same period, were used as the input parameters of the model. The analysis of satellite, field and model data showed that the evaluation of the depth of soil freezing with satellite microwave radiometry is limited by the need to conduct the contact measurements of physical properties of soil in the areas, for which the SMOS product on the brightness temperature is given.

Assessment of contemporary erosion/sedimentation rates trend within a small cultivated catchment using the radiocaesium-137 as a chronomarker (a case study from the Udmurt republic, European Russia)

This paper is devoted to revealing and estimating the contemporary soil erosion rates trend within arable lands in the south of the forest zone of European Russia, based on the study of sedimentation rates at a small dry valley bottom with almost completely cultivated catchment slopes. The dry valley catchment (0.68 km2) is located in the south part of the Udmurt Republic (the mixed forests zone) within the Izh River basin. The bomb-derived and Chernobyl-derived radiocaesium–137 was used for dating valley bottom sediments in two time intervals: 1954(1963)–1986 and 1986–2016. To analyze the causes of change in sediment redistribution rates, morphological and morphometric analyzes of the valley, the results of year-to-year observations for gully heads retreat in the catchment vicinities, hydrometeorological observations of the Russian Hydrometeorological Survey network, and also aero- and satellite images across years were used. There was a noticeable decrease in the sedimentation rates of washed-out soil material from the catchment slopes at the valley bottom over the past 60 years: from 1.8–2.5 cm/year during 1954–1986 to 0.15–0.75 cm/year for 1986–2016. Hence, the sedimentation rates have decreased by 2.5–3 times as a minimum. This trend is consistent with a decline of the average retreat rates of gully headcuts within cultivated lands in the Udmurt Republic over the past 40 years — from 1.3 m/year in 1978–1997 to 0.3 m/year in 1998–2014. We suppose that the main reason for such significant reduction of erosion rates was a increase in protective crop coefficient associated with a increase in the proportion of perennial grasses since the late 1980s. Additional contribution to the erosion reduction was owing to a decrease in surface snowmelt water runoff within the catchment area since the early 2000s, associated with the reduction in soil freezing depth and general increase in air temperature during the winter and spring months in this region of the Russian Plain.

Contemporary erosion and suspended sediment yield within river basins in the steppe of the Southeastern part of the Russian Plain: A case study of the Samara River basin

The paper presents the results of contemporary trend assessment in general erosion intensity within the southeastern steppe sector of the Russian Plain, a case study of the Samara River (the upper reaches) basin (22,800 km2, Orenburg oblast, European part of Russia), based on the long-term studying of river suspended sediment yield dynamics. The assessment is supplemented by accumulation rates field study of the soil-rill-gully erosion products in a typical small catchment (the catchment area is 1.92 km2) of the river basin using environmental radioactive caesium-137 (incl. Chernobyl-derived 137Cs) as a chronomarker. The results obtained clearly show that the Samara River’s suspended sediment yield has been reduced at least twice over the last 30 years compared with 1940–1960s. The marked decreasing trend in the erosion intensity in the Samara River basin is confirmed by a decrease (by 3.0–3.6 times as a minimum) in accumulation rates of the erosion products over the past 60 years within the dry valley bottom of the studied small catchment. The main reason for such significant erosion rates reduction was a decrease in surface snowmelt runoff within the basin area since the early 1980s, associated with a reduction in a soil freezing depth and a general increase in air temperature during spring months.