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The morphology and age of cryogenic deformations (cryoturbations and ground wedges) in the Holocene floodplain sediments of river valleys in the Selenga River basin within the areas of seasonal, discontinuous, sporadic, and isolated permafrost were studied. Late Holocene ground wedges and cryoturbations were identified in the seasonally frozen layer of floodplain sections of the Itantsa, Il’ka, and Orkhon rivers. The time of formation of the cryogenic deformations was determined on the basis of detailed morphological descriptions and dating of low and high floodplain sediments of these rivers. The age of the alluvium with cryoturbation on the low floodplain is less than 2 kyr. Cryogenic deformations on the high floodplain formed in the Late Holocene (the last 4.2 kyr). It was determined that alluvium layers with cryoturbation are underlain by moderately wet to satiated wet loamy sands and loams. Cryogenic deformations are considered a paleoclimatic indicator of the Late Holocene in the Transbaikal region and northern and central Mongolia.

The article presents the results of physical modeling of soil freezing in laboratory. The samples of silty clay of kaolinite composition were used as model soil. The main characteristics of the component and phase composition of water, as well as the heat and mass transfer and deformation properties of the soil were experimentally determined. During the physical modeling, parameters of the freezing process, differential heaving of frozen and shrinkage of thawed zones, heat and moisture transfer, and pore pressure were monitored. The appearance of segregated ice in the freezing soil, layered axial and horizontal deformation, and the dynamics of density and water content of water-saturated soil samples over time were determined using position markers and time-lapse video.

The possibility of using the dielectric method to determine the unfrozen water content in the frozen natural mineral soil was proved by establishing the relationship between the contents of soil water forms measured by the dielectric, calorimetric, and contact methods. The unfrozen water content in the sample was measured by the calorimetric and contact methods. In the dielectric method, it was estimated by measuring the maximum content of bound water. The unfrozen water content measured by the calorimetric method in the soil samples with different initial water contents varied within 17 %. The unfrozen water content measured by the contact method and the bound water content determined by the dielectric method were within the ranges of values determined by the calorimetric method. The values of the bound water content obtained by the dielectric method and the unfrozen water content obtained by the contact method differed by no more than 17 %.

Despite the low mean annual air temperature and low precipitation, subaerial suprapermafrost aquifer taliks are formed in some cases in the continuous permafrost zone of Central Yakutia. The paper presents an analysis of the seasonal and interannual dynamics of ground temperature in contrasting geocryological conditions - in areas of permafrost spread from the surface and in suprapermafrost subaerial taliks - of the key area of Levaya Shestakovka 20 km southwest of Yakutsk. The permafrost table in this area a occurs at depths from 0.5 to 20 m. The highest ground temperatures are typical of the area of aquiferous suprapermafrost taliks confined to gentle slopes composed of sandy sediments and covered with pine woodland. The thickness of the seasonally frozen layer reaches 3 m, and the depth of zero annual amplitudes varies from 6 to 12 m. Thawed deposits are preserved due to the continuous filtration of groundwater in them. The lowest ground temperatures are characteristic of the mire and the river floodplain. The depth of seasonal thawing varies from 0.5 to 1.0 m, and the depth of zero annual amplitudes exceeds 15 m. In recent years, slow freezing of the taliks from below has been noted due to mild cooling of the strata underlying the thawed aquifers. Beyond the area of taliks, weak multidirectional changes in ground temperature have been recorded.

Based on observations on 12 largest rivers of East Siberia (Lena, Vilyuy, Kolyma, Aldan, Olenek, Vitim, Indigirka, Amga, Olekma, Anabar, Yana, and Chara) during summer low-water runoff in 2007-2011, the main features of the chemical composition and physical properties of river water have been determined. It is found that favorable oxygen regime, higher chemical oxygen demand and color of water, higher concentration of total iron and ammonium ions, and moderate salinity are characteristic of the investigated rivers. The territory of East Siberia is characterized by an ubiquitous distribution of permafrost. The thickness of seasonally thawed layer within river catchments is extremely variable in the studied region. Using canonical-correlation analysis, it was found that concentrations of specific components of ionic constituents (water hardness, calcium, magnesium, bicarbonates, sulfate ions, and salinity) depend on the active layer thickness (ALT). Herewith, the deeper the active layer in a catchment, the higher the concentration of mentioned components of ionic constituents. This pattern is explained by the fact that permafrost serves as a confining barrier that prevents infiltration of surface water through deep mineral horizons thus restricting water saturation with mineral ions. The increase in ALT noted in recent decades in the permafrost zone of the northern hemisphere may continue in the current century. Therefore, knowledge of how the concentration of soluble biogeochemical constituents in the rivers depends on ALT of permafrost in the catchments is valuable for assessment of potential changes in the chemical composition of river water in the permafrost zone in the future.

To date, the issue of using ice-based composite materials for engineering constructions under harsh weather conditions remains poorly understood. Application of ice as construction material is favored by its ease of use and low manufacturing cost. In turn, ice can be reinforced with various additional materials that change its physical and mechanical properties as part of an ice-based composite material. The results of an experimental study of the behavior of reinforced ice beams under pure bending are discussed. As a reinforcement, longitudinal rods with different physical and mechanical characteristics made of fiberglass and polypropylene were used. The results of the study were compared with previous experiments on loading ice beams reinforced with steel armature. It is concluded that the proposed materials can be efficiently used to improve the mechanical characteristics of the ice. There is a positive effect of polypropylene on the deformability of the samples, as well as their bearing capacity. Schematic diagrams of deformation of ice beams reinforced with steel and fiberglass reinforcement and with polypropylene rods are presented. Prospects for the use of fiberglass and polypropylene rods in the ice-based composite materials are discussed.

The article presents the initial assumptions of the predictive model of changes in the temperature regime of the frozen soil massif in the case of surface flooding. Heat exchange of the soil surface with the atmosphere through a shallow (up to 1 m) water cover is described using an effective heat exchange coefficient, which includes the intensity of mixing of the water layer during the summer season. The results of calculation of two parameters of the new thermal condition of the frozen massif (temperature at a depth of zero annual amplitude and the maximum depth of seasonal thawing) appearing as a result of flooding are presented. In addition, the rate of transformation to the new condition is considered. Significant warming of the frozen foundation soil occurs in the case of intense mixing of the water layer during the summer season. If the mixing process does not take place in the water reservoir of a shallow depth, its cooling effect is possible. In deeper reservoirs, the warming effect is possible, but it is weaker than that under mixing conditions. This analysis has been performed for the least studied element of the “roadway embankment - reservoir - frozen soil” technical system in order to control the correctness of the calculation procedure in a more complex case for a two-dimensional process. The results of mathematical modeling of the temperature field in the frozen base of the roadway in contact with shallow water basin are presented. It is demonstrated that the frozen base warms up essentially, if the water layer is intermixed intensively (by wind) in summer time. The initial temperature state may be preserved during the whole period of road exploitation, if the summer mixing of water is blocked by fairly simple technical measures that are proposed in this paper.

Data on the snow cover in the middle and southern taiga subzones of the northeast of European Russia (Komi Republic) are analyzed. Field surveys were carried out in the second half of March in 2005-2007 and 2014-2015 on open flat spaces and in the intercrown spaces of forest stands. The studies were conducted at the same monitoring points, which allowed for a correct analysis of spatial and temporal differences. By route observations, measurements of the snow depth and snow density were carried out, and the values of snow water equivalent were calculated. The obtained data were compared with the results of measurements at the stations of the federal meteorological service. Schematic maps of spatial distribution of snow cover parameters were constructed. The influence of the landscape on snow accumulation was shown: snow depth increased in intercrown spaces of forest stands; in open areas, snow compaction with a decrease in snow depth took place. The wide territorial distribution of measurement points made it possible to estimate the longitudinal effect and the related relief conditions on the snow cover parameters. The maximum snow accumulation was observed along the Ural Mountains in the eastern part of the study area, where intense moisture condensation and precipitation take place. Snow depth and snow water equivalent in the foothills increased to the east. At the same time, the zone of increased snow density was noted in the western part of the Komi Republic. The obtained field data are consistent with long-term observations by other authors, as well as with the results of measurements at the network of weather stations.

Thermokarst plains with fluvial erosion include two genetically different types of surface: slightly undulating watersheds and lowered surfaces of khasyreys (drained thermokarst lakes with secondary thermokarst lakes). The research deals with a comparative analysis of statistical distributions of the areas of thermokarst lakes and secondary lakes. Using statistical criteria and remote sensing data for eight key sites in different natural conditions, such as Yamal and Taz peninsulas, the Kolyma Lowland, and the Penzhina River valley, we determined statistically significant differences in the area distributions of thermokarst lakes within different genetic types of the surface. Statistical analysis shows that the areas of thermokarst lakes correspond to an integral-exponential distribution. This allows us to conclude that a dynamic equilibrium is established within each type of the surface in the course of the initiation, growth, and drainage of thermokarst lakes. Though the parameters of thermokarst lakes differ significantly, we find a correlation between the distribution parameters of lake areas within the main surface of thermokarst plains with fluvial erosion and the surface of khasyreys with secondary lakes.

Information about the life and work of an outstanding scientist Mikhail Ivanovich Sumgin is presented. His contribution to the development of a young science of frozen rocks and related phenomena-geocryology is discussed.