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The comparative analysis of data available from open sources on the water spectral lines intensities in the frequency range from 0 to 1.75 THz has been carried out. The calculations by the method of effective Hamiltonians and the variational method, as well as experimental data were taken into account. It has been established that the intensity uncertainty is less than 2% for lines in the ground vibrational state with an intensity of more than 10^-27 cm/mol. and is about 5-10% for weaker lines. For strong (more than 10^-26 cm/mol.) lines in the ν₂ state, the uncertainty ranges from 2 to 5% and increases to 5-10% for weak lines. For all lines in the 2ν₂, ν₁, and ν₃ states, the uncertainty is no more than 5-10%. The presented data show that most of the considered lines can be assigned a higher (by 1-2 steps according to the classification adopted in HITRAN) category of intensity accuracy.

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 %.

This paper reports on the hydrogeological conditions and groundwater regime in the Lena River floodplain near Yakutsk. The published and archive materials, including field data collected by the authors in 2013-2021, were analyzed. Data from more than 70 boreholes were examined to characterize permafrost and hydrogeological conditions in the area. Data on groundwater level monitoring in the reclaimed area of the floodplain were also used. Over 250 sample analyses were interpreted to characterize the chemical composition of surface and ground waters. The results suggest that suprapermafrost waters in the high floodplain are recharged both by infiltration of river water and by a transit water flow under the river channel hydraulically connected to floodplain taliks. The seasonal and spatial variability of the chemical composition of waters was revealed in the Lena River and in the studied taliks. The surface and ground waters of the Quaternary aquifer on the east bank of the Lena River are characterized by the lowest total dissolved solids (TDS) concentration (0.1-0.3 mg/L) and by the magnesium-calcium chloride-bicarbonate composition. These waters are recharged by fresh water of the supra- and interpermafrost taliks of the Bestyakh terrace and by the riverbed taliks under small rivers. In the vicinity of Yakutsk, TDS concentrations in the Lena River and in the Quaternary aquifer increase to 0.5-1.3 g/L due to high mobility of chloride and sulfate ions migrating with the surface and suprapermafrost runoff from the low terrace, where the city is located.

High rates of degradation of the Bolshoy Azau Glacier on Elbrus make it necessary to assess the development of lakes on the ice-free land and on the glacier itself. For this purpose, aerospace data for the period of 1957-2021, as well as information from visual observations, Internet sources, and tourist photographs were analyzed. The existence of 15 lakes with an area of 0.14-20.25 thousand m² on the Bolshoy Azau Glacier and the adjacent territory was recorded at various times. The long-term existence of the lake in contact with the glacier on the Echo of the War mountain passage covering with an area of up to 4.5 thousand m² was revealed for the period of 1971-2009. The maximum area (20.25 thousand m²) was detected on a satellite image from June 25, 2009 for a lake on the dead ice part of the median moraine between left and right ice streams of the Bolshoy Azau Glacier. In the hollows on the glacier surface, up to three lakes with a maximum total area of 7.86 thousand m² were observed in different times. Lakes on the Bolshoy Azau Glacier appeared mainly during the snow cover melting, while masses of drifted snow served as dams in the drainage area of hollows. These lakes disappeared after melting of drifted snow dams and/or in the course of drainage through subglacial and underground runoff channels.

The probabilistic-statistical method is applied to study the causes of the thermokarst distribution heterogeneity along the long linear constructions. A list of natural conditions affecting the development of thermokarst along an oil pipeline is discussed. The methodology for zoning buffer area of long-distance linear constructions (e.g., oil pipeline) according to the conditions of thermokarst development is substantiated. We have delineated thermokarst-susceptible and thermokarst-tolerant areas along the oil pipeline buffer zone according to the environmental conditions.

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.