Home – Home – Jornals – Earth’s Cryosphere 2024 number 6

This article presents the results of a comprehensive investigation of the ice complex discovered within the strath terrace in the lower course of the Vilyui River, Central Yakutia. On the basis of chemical, isotopic, granulometric, palynological, and radiocarbon data, it has been revealed that the formation of the ice complex took place from the end of the Kargin (MIS-3) and throughout the Sartan (MIS-2) epochs of the Late Pleistocene (between 29 and 11.7 ka BP) under cryoarid conditions with a predominance of dry cold xerophytic steppes and, locally, forb-grass meadows. Mineralization of syngenetic ice wedges is low (0.07-0.29 g/dm³), and a predominance of calcium bicarbonates suggests that winter precipitation - snowmelt water - was the main source of wedge ice. The increased content of heavy metals (Fe, Mn, Co, V, Sr) indicates that the formation of ice wedges also involved the water of shallow freezing lakes confined to the polygonal microrelief. The ice wedges have a relatively light isotopic composition (δ¹⁸О -(29.2 ± 0.3)‰ and -(27.2 ± 1.4)‰; δD -(226.6 ± 2.3)‰ and -(215.8 ± 8.5)‰, d_exc (6.8±0.51)‰ and (1.7±3.1)‰), which is close to the composition of modern atmospheric precipitation of the cold season and spring snow storage in Yakutsk. These data attest to dry and cold conditions, thin snow cover, and moisture deficiency in cryogenic landscapes during the formation of the ice complex.

Calculating the water balance for lakes in the mountains is difficult due to insufficient observation data and poor knowledge of a number of runoff formation processes. The hydrological regime of high-mountain lakes is determined, on the one hand, by climatic factors, and on the other hand, by the characteristics of the underlying surface of catchments with different ratios of glacial and non-glacial parts. In this article, based on data from field hydrological, meteorological, and glaciological observations, the water balance was calculated with a daily step for a periglacial lake located in the Southern Chuya Ridge (Central Altai). Calculating the water balance made it possible to estimate the contribution of meltwater from glaciers and snowfields and of precipitation to the total inflow of water to the lake and to identify the features of the meltwater inflow from glaciers into the lake. The predominant role of subsurface runoff in the incoming part of the lake water balance has been revealed.

Studies show that frozen rock strata can accumulate significant amounts of natural gas both in free form and in the form of gas hydrates. Changes in the thermobaric conditions of gas-bearing permafrost can be accompanied by various gas-dynamic processes that lead to active gas emissions from the upper horizons of permafrost. During the activation of these processes, the gas pressure in gas-saturated horizons can be equal to or even exceed the pressure of the overlying rocks, and pressure gradients can reach a significant value that will be sufficient for deformation of ice- and hydrate-containing rocks, the occurrence of gas filtration, its permeation and breakthrough into the overlying rock layers. To simulate such natural conditions, the authors developed an original technology that included the creation of a special core holder for the filtration system and the development of an algorithm for conducting laboratory tests. In the course of methodological experiments, it was found that at a constant gas pressure of approximately 2 MPa in a heated impermeable ice-saturated sandy clay sample, gas filtration can occur in the region of high negative temperatures, below its thawing temperature. Methodological experiments to study the changes in the gas permeability of frozen and thawing rocks under conditions of the formation and dissociation of methane pore hydrates have shown regular changes in gas permeability due to ice (water)-hydrate phase transitions and structural transformation of the soils caused by these phase transitions.

Based on data from route snow surveys, the average long-term values of snow density at the time of the maximum snow cover depth and for individual months were determined for the continental part of the Russian Arctic. A comparison of snow densities was made for the climatic periods of 1966-1990, 1991-2020, and 2011-2020; on average, they comprised 0.265, 0.264, and 0.267 g/cm³, respectively. A comparison with the historical climatic period of 1966-1990 indicates that current changes in the maximum snow density in the Russian Arctic are insignificant: a decrease by about 1%. The greatest decrease in snow density is noted in the north of Yakutia, and the most significant increase in snow density is observed in the north of Western Siberia. Snow density values for individual months indicate that, owing to the later dates of snow cover establishment, the most significant changes in snow density take place in the autumn period. On average, snow density in 1991-2020 compared to that in 1966-1990 decreased by 6% in October, 10% in November, 2% in January, and 5% in May. An increase by 1% took place in March. Along with the changes in snow density for individual months, a change in its dynamics - the ratio of snow density for individual months to its maximum value - was also observed. In November 1991-2020, this ratio decreased by 15-20% in a number of Arctic regions in the European territory of Russia and up to 25% in the north of Yakutia in comparison with that in November 1966-1990. Maps of snow density and its variability have been constructed.

The results of a study of the relationship between evaporation from the soil surface and atmospheric precipitation during the warm seasons of 2015-2016 and 2019 at the Tyimaada geocryological research station in Central Yakutia are analyzed. The volumes of evaporation from the soil surface and precipitation›s amount and chemical composition were studied. The average evaporation was 1.37 (0.33-3.13) mm/day, exceeding precipitation by about 40%. The intensity of evaporation was especially high in the first month of the warm season (May), which was associated with the thawing of frozen soil and the seepage of meltwater from snow into the seasonally thawed layer. The bicarbonate calcium chemical composition of atmospheric precipitation during the summer remained stable, but the degree of mineralization decreased by 20-40% by autumn. The content of most chemical elements in precipitation was higher in May-June and decreased in the second half of the warm season. The greatest contrasts in the concentrations of chlorides, sulfates, sodium, and ammonium in the atmospheric precipitation were observed during the periods of maximum and minimum evaporation from the soil surface.

The use of phyto- and bioindicators for interpreting geoelectric data in the study of permafrost sections is substantiated. The research used electrical resistivity tomography and ground-penetrating radar methods in various climatic and geocryological conditions from the Tien Shan to the Magadan region. In each region, specific landscape features of geocryological conditions were identified and compared with geoelectric sections or ground-penetrating radar data. Certain types of larch stands in Central Yakutia and birch stands in Transbaikalia together with data on high rock resistivity indicate the presence of permafrost with reduced temperature. In the northeast of Russia, poplars and willows (chosenia) grow in the area of talik zones, which allows interpreting areas of low electrical resistivity of rocks under them as taliks rather than the areas with pyritization or increased clay content. In the Tien Shan, a correlation was established between the electrical resistivity of a rock glacier and its age indicated by the size of Rhizocarpon sp. lichens. In mountainous areas, anomalies of low resistivity in places, where large anthills are concentrated, indicate the deep occurrence of permafrost table or open taliks in fault zones. Thus, taking into account landscape indicators of geocryological conditions helps us to reduce the ambiguity of geological interpretation of geoelectric data.