Review: On the basis of theoretical calculations of insolation and Earth remote sensing data on the dynamics of the sea ice area in the Arctic ocean, a close relationship between long-term changes in the sea ice area and annual insolation contrast in the Northern hemisphere was determined. The change in insolation contrast was generalized (in terms of the source and sink of heat) reflects the change in the meridional insolation gradient that regulates the meridional heat transfer in the ocean - atmosphere system. The regression model was used to make an estimated forecast of changes in the area of sea ice in the Arctic Ocean. According to our estimates, the reduction of the average annual sea ice extent in the Arctic Ocean in 2050 will be 18.3% relative to 2018. The Maximum area (March) will be reduced by 10.1%, and the Minimum area (September) by 60.3%. The decrease in the area of sea ice is associated with an increase in the meridional gradient of insolation and meridional heat transfer resulting from a decrease in the inclination of the Earth's rotation axis in the present epoch.

Keywords: Earth insolation, satellite observations, sea ice, meridional insolation gradient, insolation contrast, meridional heat transfer, regression model, estimated forecast, sun radiation, Arctic

Review: The aim of the study is to estimate the Amderma station (the Kara sea) ice-free period using sea ice concentration satellite datasets in comparison to observation data. The work follows the research performed for the Western Coast of the Yamal (Marresalya) being the part of the Arctic coastal dynamics study. The OSISAF, JAXA and NSIDC (resolution 25 km, 1 day, 1979-2018) sea ice concentration datasets were used to characterize the water area, adjacent to the station within the 30-50 km radius .
The threshold (15%-concentration) and the author's "sliding window" methods were used to detect open water start and end dates.
According to the satellite data the ice-free period in the 30-50-kilometer water area along the Amderma coast is shifted by 2-3 weeks closer to December if compared to observations.
At Amderma station (in the contrast to Marresalya), there are no significant trends in ice-free period start dates. On the adjacent water area, the destruction of the ice cover occurs earlier by by 3-6 weeks if compared to the 1980s, and the end date - by 3-6 weeks later. The duration of the open water period over 40 years has increased by 32-36 days at the station and by 52-120 days (40-100%) in the adjacent water area.

Keywords: ice-free period, open water period, sea ice concentration, satellite datasets, Arctic coasts, Kara Sea, Amderma, climate change, open water period duration, coastal dynamics

Review: Massive ice is widespread on the territory of modern of Eurasian permafrost area: in the north of Western Siberia, Taimyr, Chukotka, Arctic islands. Their thickness reaches 45-50 m. The origin of massive ice is difficult to define due to the equifinality of such two different processes as intrasedimental freezing and formation of glacial ice, in both cases thick massive ice is formed in various ways but with the same final appearance. Three important aspects that show the evidence of the intrasedimental origin of massive ice in the north of Eurasia are examined. At first glance they are obvious, but nevertheless fell out of sight of paleogeocryologists. It is shown that: 1). Any currently existing Late Pleistocene glacier or part of it located under Holocene ice have not been found yet within the Eurasian Arctic, neither on the Arctic islands with ice sheets, nor in the mountainous regions; 2). The isotopic composition of the vast majority of massive ice found in northern Eurasia is quite "Holocene", whereas in the north of Canada and Alaska, ice with a very light isotopic composition can often be found; 3). It should be taken into account that massive ice is found in the Holocene sediments of Western Siberia and Chukotka, where there is no reason to assume the glaciers spread to the plains.

Keywords: massive ice, glaciers, ice caps, intrasedimental ice, buried ice, equifinality, oxygen isotopes, deuterium, Eurasian Arctic, Canadian Arctic

Review: Massive ice, located at different depths in the permafrost of the Kharasavey gas condensate field, many massive ice bodyes occured in different forms such as layers, lenses and laccoliths. Massive ice near the Kharasavey village was repeatedly studied and tested in detail, and ice bodyes were found both within the first sea terrace and within the third sea terrace also. The isotopic and chemical composition of massive ice can be interpreted by different ways. We believe that it indicate intrasedimental formation of massive ice. This study is based on data on the values ​​of δ18Î, δ2H and dexc in massive ice as well as the chemical composition of the ice to establish possible conditions for the massive ice formation. Geochemical studies of sediments within the coastal areas of the Kharasavey showed that variability in the distribution of salts in sediments reaches a maximum here, especially in the transition zone from sea to land. The isotopic and chemical characteristics of the ice indicate that ice had been formed in an open system (i.e., with free flow of water from the reservoir). At the same time, the water in the reservoir was changed, at the first stages, most likely, it was a mixture of sea and fresh water, which was subsequently desalinatind more and more.

Keywords: massive ice, ice formation, ice, isotopes of oxygen, isotopes of hydrogen, open system, closed system, deuterium excess, ground, genesis

Review: Studies of the dependence of the accumulation of stable carbon isotopes on the growing conditions in modern plant species of tundra are very relevant. It was found that the same plant species accumulate the stable 13C isotope in different ways. The goal of this work is to reveal the relationship between the content of the stable 13C isotope in modern plants and the natural conditions of typical terrains of the tundra of the Western Yamal. At the geocryological station Marre-Sale, modern plant species were selected that grow under conditions of different moisture and remoteness from the sea. Modern plant species were determined using determinant atlases, carbon isotope contents using a DELTA V Advantage isotope mass spectrometer in the laboratory of LBIT (IMCES SB RAS). In different tracts for identical plants, the distribution of carbon isotopes depending on moisture was confirmed: the heavier 13Ñ accumulates in dry ones, and lighter in humid and moist ones. It was found that near the sea, the same plants of dry and wet tracts accumulate heavier 13Ñ due to the influence of marine aerosols.

Keywords: moisture, carbon, tundra, growing conditions, modern plants, bioforms, isotopic composition, 13Ñ plants, marine influence, analysis of variance

Review: The subject of this study is the ratio of carbon and nitrogen content in the soil of lithalsa landscape in the Sentsa river valley. The focus is on the spatial distribution of C/N ratio in the genetic soil horizons: humus (A), illuvial (B), the parent rock(C), and also in the buried peat horizon (T). The carbon and nitrogen content is analyzed in 70 samples using the element analyzer C, H, N, S –O EA 1110. Sample preparation included drying the soil through a sieve and rubbing it with a rubber pestle in a porcelain mortar. It is found that cryogenic concentration of soil solutions, cryogenic heaving, thermokarst, zoogenic turbations, peat burial, and alluvial loam deposition are the main processes determining the peculiarity of soil formation within lithalsa landscapes. The maximum variation in the ratio of carbon and nitrogen content is observed in the illuvial horizon, while in the humus horizon and in the parent rock, as well as in the buried peat horizon, this indicator is in a smaller range.

Keywords: lithalsa, buried peat, parent rock, illuvial horizon, humic horizon, soil, nitrogen, carbon, entic podzols, cryosol

Review: The subject of the study was to determine the causes of long-term deformation of the structures of technological equipment inside the building of the pumping station providing water supply to industrial facilities and residential buildings of the infrastructure of the Zapolyarnoye oil and gas condensate field located in the permafrost zone of Western Siberia, near the Arctic circle. The main objectives of the study were to identify the mechanism of these deformations and develop practical recommendations for stabilizing structures and preventing their further destruction based on the analysis of the results. The survey was carried out using a set of methods provided for by the current legislation (visual and measurement control, geodetic works, thermometric observations in wells). The current situation at objects of such importance at the time of our study had no analogues. The analysis of the results of the inspection of the structure leads to the conclusion that the cause of the deformations were miscalculations in the design, construction and operation of the structure. This should be done with the participation of specialists in the field of engineering permafrost.

Keywords: permafrost, Zapolarnoe, field, pumping, station, urvey, deformation, thawing, deposition, soil

Review: Abstract: The object of the study is the permafrost soils of the section of the route of the main water pipeline «Tabaga-Byuteidyakh» in rural areas of Central Yakutia, with a length of about 28 kilometers. Permafrost soils are widely developed in the South-Eastern part of Central Yakutia and are located on the Leno-Amginsky interfluve. They lie in the upper part of the geological section and are underlying on the lane of the main water pipeline route, as well as fall into the foundations of engineering structures of industrial facilities and hydraulic engineering construction. The study is based on a complex of field engineering and geological surveys and laboratory studies of the physical and mechanical properties of rocks.The article discusses the features of the composition, structure and properties of rocks in this area, it is noted that among the considered soils there are a variety of granulometric types, cryogenic texture from massive to layered, usually clay soils have a higher ice content than sandy ones. Technogenic loads are also mentioned, in the form of objects of the main water supply system consisting of pumping stations, pipelines, reservoirs and channels, which lead to significant changes in the geocryological environment and surrounding landscapes.

Keywords: permafrost soils, physical and mechanical properties, ice content, cryogenic texture, thermokarst, polygonal microrelief, ground ice, frost cracking, pingo, main water main