Home – Home – Jornals – Earth’s Cryosphere 2022 number 2

The article integrates the results of half a century studies of Late Pleistocene-Holocene changes in climate, sea level and glaciation in the marginal zone of Antarctica in order to identify the chronology, parameters, mechanisms of these changes under the influence of global, regional and local factors. During the interstadial (MIS 3), the natural conditions here resembled modern ones, and the sea level in some areas exceeded modern marks. The development of glaciation of the marginal zone from about 26 000 years BP went on when the temperature fell and the sea level dropped by 30-50 m. The growth of glaciation on the shelf outpaced the growth of ice on the outskirts of the continent, leading to a moisture deficit in the interior regions. During the LGM, there was a thin (less than 300 m) glaciation of coastal and mountainous land areas, and a thick (more than 1000 m) glaciation on the shelf. Deglaciation of the marginal zone began about 17 000 years BP due to rising sea level and global warming. Holocene climate changes in most areas had a general trend: warming in the early Holocene to about 8000 years BP and 4000-2000 years BP, cooling 2000-1500 years BP, but also had local differences. The relative sea level rose in the regions from the early Holocene to the period 8000-6000 years BP; then it fell with a decrease in speed and even with a possible rise of the level 2500-1300 years BP; local differences in the amplitudes and course of the level were determined by local tectonics and dynamics of deglaciation. Deglaciation rates were high from the early Holocene to about 7500 years BP due to warming and marine transgression; then the speed dropped. The advance of outlet and shelf glaciers 6500 and 4500 years BP was associated with a decrease in sea level and cooling. In the period 4000-1000 years BP, outlet and shelf glaciers could also respond to changes in sea level, and ice domes expanded according to the “warming-increasing humidity-increasing snow and ice accumulation” pattern. During the Little Ice Age, moraines were created in some areas, registering a slight increase in glaciers due to cooling.

Data on the width of floodplain taliks in river valleys of the mountainous areas of the northeastern part of Russia and in some adjacent areas of the Far East were gathered and organized. The investigated region extends from the Arctic coast to the southern limits of the continuous permafrost area. To assess the talik width, the satellite images (possessing high resolution) of Google Earth and previously established landscape features were used. The catchment areas at downstream ends of the chosen 340 representative river sections varied from less than 10 to more than 200 000 km², talik widths - from 41 to 4100 m. The rivers were subdivided into 4 channel types according to the degree of its branching based on the previous studies confirming that the floodplain taliks were formed only by braided rivers on coarse-grained alluvium. The studied sites are generally evenly distributed both over the territory and according to the selected channel types. The changes in talik widths from marginal coastal to the central continental basins in relation to the river types are discussed in this paper. The parameters of the empirical power-law dependence of the talik width on the catchment area of the river are calculated. The obtained results assess a variation of the melting zone width within a given river catchment area and determine the most probable minimum value of this parameter. In future, the approaches used, in combination with the field research, will contribute to the improvement of remote decryption methods.

We studied the distribution of fluoride (F^-) in fresh and moderately mineralized waters of subpermafrost aquifers of Central Yakutia. We analyzed the data archive of 296 water samples collected by the Melnikov Permafrost Institute staff members during hydrochemical surveys between 1984 and 2019. The average fluoride concentrations varied between 5 and 10 mg/L. Highest concentrations (up to 15.5 mg/L) are observed in waters of the terrigenous aquifer systems occurring over the crystalline basement. The sources of fluoride can likely be the various fluoride-bearing minerals of aluminosilicate rocks. The high fluoride concentrations in these aquifers are associated with geochemistry (alkaline environment and sodium-bicarbonate water type) resulted from cryogenic metamorphism of rocks. Lowest concentrations (0.4-0.8 to 2-3 mg/L) are observed in subpermafrost groundwater samples collected from wells near the Lena River channel. These low concentrations indirectly indicate the presence of open taliks beneath the channel and the infiltration of stream water into the subpermafrost aquifers.

The territory of the north of Western Siberia is known as one of the promising regions of the Russian Arctic in terms of reserves of alternative fuel sources, in particular, gas hydrates. According to the results of interpretation of the data of 3D transient electromagnetic method (TEM) in the cryolithozone, performed in the Nadym district of the Yamalo-Nenets Autonomous Okrug at depths of 100-220 m, geoelectric anomalies of increased electrical resistivity values were revealed, accompanied by the induced polarization anomalies. The authors associate the mentioned anomalies with the possible accumulations of gas hydrates in the cryolithozone. To justify the applicability of the transient electromagnetic method in the near field zone in a shallow modification for mapping subpermafrost geoelectric anomalies in the cryolithozone, a description of a mathematical experiment is presented in the paper. The experiment is based on empirical electromagnetic data. As a result of mathematical modeling, it is shown that the use of transient electromagnetic method makes it possible to estimate the conductivity and polarizability of the upper part of the section of the study area and to identify anomalies in the cryolithozone, which are probably associated with hydrate-bearing deposits.

This analytical review is devoted to the Vladimir Romanovich Alekseev’s monograph dedicated to kurums - a specific type of covering coarse deposits, widely distributed within the mountainous permafrost areas of Northern Asia.