Home – Home – Jornals – 2018 number 6

The data inferred from a new key section in the basin of the Vilyuy river allowed us to examine the structural-faces features and absolute age of cross-layered sandy-loam sediments of the D’olkuminskaya series distributed in Central Yakutia in a wide hypsometric range. These deposits had formed in the period from the latest Kargin thermochron to the beginning of the Holocene (between 35 ka and 12-10 ka BP) under the overwhelming conditions of severe desiccation and desertification of the area. During the Boreal optimum of the Holocene, the soil-vegetation cover had largely provided for the stabilization of dune covers. The formation of the contemporary moving-dune massifs had taken place not more than one thousand years ago and had been directly linked with the climatic events of the Little Ice Age.

The study has been focused on the thermal regime of peat soils (fibrist histosols) of palsa bogs and peat plateaus in northern West Siberia. Autonomous loggers recorded temperature for 343 days every hour to a depth up to 60 cm in palsas and 120 cm in hollows (pools, lawns) in four mire ecosystems: the forest tundra hollow and palsa, and the northern taiga hollow and palsa. The data on the mean daily temperature, the mean annual temperature, the extremes, the annual amplitude, the active layer dynamics, the sums of positive and negative temperatures at different depths have been adduced. The established differences in the thermal regimes of soils were due to the differences in the ecosystems of mires, rather than in bioclimatic zones they belong to. The high-latitude mires have the largest impact on the annual amplitude and temperature parameters obtained for the cold period.

Long-term and seasonal variations in major- and trace-element compositions of groundwaters in anthropogenic cryopegs stripped by boreholes in unconsolidated alluvial sediments have been monitored for thirty years at a site within Yakutsk city. Suprapermafrost cryopegs became less saline for the past five to seven years as a result of climate change in many previous years. The obtained data on chemistry and flow dynamics of groundwaters indicate enhanced hydraulic connectivity of cryopegs in the active layer. The ongoing ground temperature warming will lead to general decrease in the contents of highly soluble salts in suprapermafrost cryopegs and to increase in trace element abundances in pore waters.

The paper presents the estimates of evident ground ice contained in the permafrost of the Tien Shan Mountains based on the available geocryological maps of various scales. The maps represent patterns of permafrost distribution reflected in the regional structures depending on geocryological zonality. Using the data on the areal extent, thickness and ice content of permafrost, the volumes of permafrost and ground ice have been determined. It has been revealed that the largest volumes of ground ice occur in active rock glaciers and recent moraines. The volume of glaciers relative to that of ground ice has been ascertained to decrease signifi cantly due to the glacial degradation.

The spatial distribution of soil СO2 efflux measured at Novyi Urengoy station in southern tundra (Taz Peninsula) is determined by the soil volumetric moisture content and water-extractable organic carbon and with elevations above sea level. The contents of soil water-extractable and microbial biomass carbon are highly variable over the territory. The spatial distribution of the soil microbial carbon content partly depends on organic layer thickness and soil moisture, which are responsible for 19 % and 8 % of its variance, respectively. The environmental factors of active layer thickness, soil volumetric moisture, and soil surface temperature are relatively stable as the soil and vegetation covers are homogeneous while the soil organic layer is thin.

Changes in the equilibrium line altitude (ELA) of glacier systems have been studied in the Suntar-Khayata, Chersky and Orulgan mountains, as well as over the whole territory of Northeastern Siberia, for three periods of time: 1930-1960, 1961-1990 and 1991-2012. Northeastern Siberia has undergone warming in the 21st century which became more rapid than in the previous fi fty years. Records at most weather stations show increasing trends in mean annual and summer air temperatures and in total atmospheric precipitation but a decreasing trend in solid precipitation. The climate change has led to a rise of glacier ELA almost all over the Northeastern Siberia and to an increase in ablation which is in balance with accumulation at this altitude. The ELA rise is from 100 to 450 mm, 200 ± 50 m on average, while the ablation (accumulation) increase is 50 to 250 mm in different periods. The glacier parameters inferred from climatic data are background values, which provide a general idea of current and potential changes in glacier systems in this poorly studied region.

The results of measurement of snow cover density for the period from 2005 to 2017. The data on snow density have been obtained during regular observations carried out on a stationary horizontal sites located in Yuzhno-Sakhalinsk and during field work. 227 snow pits have been sampled, and more than 2,000 values of snow density for different snow layers have been analyzed. Data on distribution of snow density in different landscapes have been compiled and structured. The maximum density of snow is typical for treeless regions with dominating strong winds. Typical densities for specific snow structure have been revealed. The density of snow layers have been found to vary depending on the type of snow in the range from 40 kg/m³ (newly fallen snow) up to 790 kg/m³ (ice crust).