Received April 26, 2023; revised August 18, 2023; accepted October 2, 2023This article presents the results of estimating the scale of the present-day glaciation of the Mongun-Taiga Mountain range (Eastern Altai) based on the decoding multi-time satellite images, GPR data and modelling using GlabTop2 and the Volume-Area Scaling (VAS) method. By 2021, 38 glaciers have been identified according to the hydrological principle and 36 ones – by the morphological principle. The total area is estimated as 17.18 ± 1.13 km2. Since 2010, area of the glaciers has decreased by 15%. The thickness of the glacial complex on the main peak of the Mongun-Taiga Mountain range was measured in the ablation season of 2021. More than 6 km of profiles were obtained by the GPR survey with accuracy of about 1%. Based on these data, the GlabTop2 model was calibrated. Then the spatial distribution of the ice thickness was obtained over the entire massif. The total volume of ice in the flat-summit glacier № 17 is estimated at 0.202 ± 0.008 km3 of ice. According to the GlabTop2 model with the morphological approach the ice volume of the whole massif was estimated at 0.733 ± 0.052 km3, and with the hydrological approach: 0.888 ± 0.061 km3. Determination of the boundaries of glaciers by the VAS method gave larger values: 0.690 ± 0.038 km3 with a morphological approach and 0.757 ± 0.036 km3 with a hydrological method. Consequently, with the same area of glaciers, volume determined by two different approaches can be rather different. This has a decisive influence on the morphological structure of ice reserves: the role of large forms of glaciation sharply prevails with the morphological approach. Most of the ice is contained in glaciers of the flat summit (27–40%). With the hydrological approach, which is used most often, the role of small forms of glaciation is overestimated. At the same time, the contribution of flat-summit glaciers is estimated at only 2%.

The results of the analysis of the relationship between the width of annual tree rings of various woody plants and snow cover characteristics are presented: the dates of setting-up and destruction (loss) of stable snow cover, the duration of its existence, the thickness and water content of snow cover for the period of maximum snow accumulation. The studied areas are the forest-tundra zone, the northern taiga subzone, the southern forest-steppe subzone, and the dry steppe subzone within boundaries of the West Siberian Plain. Data from observations of snow cover on routes and meteorological sites of Roshydromet for 1966–2020 (for forest tundra and northern taiga) and 1966–2018 (for forest-steppe and dry steppe) together with dendrochronological samples obtained by the authors in these natural zones and subzones were used for this study. It was found that the thickness and water content of the snow cover play greater role for the radial growth of trees in the forest-tundra and dry steppe as compared to the northern taiga and southern forest-steppe. In the dry steppe, the trees of the upper parts of the low ridges and flat interfluves (plakors) are more sensitive to these snow cover characteristics, while in the forest-tundra this is important for the lower parts of the slopes. The dates of destruction of stable snow cover are more significant in the southern regions than in the northern ones. In the southern forest-steppe, the early loss of the snow cover increases the rate of growth of tree rings, while in the dry steppe it weakens it. The dates of setting-up of the stable snow cover are more important for the growth of trees compared to the dates of its loss, especially in the forest-tundra and southern forest-steppe since the later it starts, the greater the growth of trees. Importance of the duration of the period with stable snow cover for tree growth is higher in the southern regions. Its increasing in the southern forest-steppe reduces the growth of trees but increases in the dry steppe.

The conducted studies allowed us to obtain a detailed picture of glaciation changes in the mountain regions of Russia, most provided with information about glaciers in the twentieth century. For the Caucasus glaciation, the data were obtained for the time periods 1911, 1952, 2000, 2014, 2018 and 2020; for Altai – for 1850, 1952, 2003 and 2018. For large glaciation nodes of the Central Altai – Katun, South and North Chuya Ridges additionally for 1968, 2008, and 2017. In both areas, a decrease in the area of glaciers since the beginning of the twentieth century and acceleration of the rate of reduction in the early twenty-first century have been revealed. The glaciers of the Caucasus and Altai reduced their size during this time by 46% and 48%, respectively. On average, in the twentieth century the glaciers of the Caucasus lost about 0.2% of the area per year, in the Altai – 0.15%, and in the early twentieth century 1.15 and 1.7% respectively. To study Kamchatka glaciers, we used data from the Glacier Inventory of the USSR (1950/1957) and images from different satellites in the period 2007–2019. The glaciers that were not previously registered in the Glacier Inventory of the USSR were identified. The greatest number of such glaciers is in the northern part of the Midnight Ridge, where out of 465 glaciers identified on modern satellite images, 216 were not included in the Glacier Inventory of the USSR. The area of glaciation in different regions of Kamchatka has changed extremely unevenly since the first cataloguing, which is associated with significant differences in glacier morphology. Glaciers of volcanic areas increased their size or remained stationary; here there is no tendency for glaciers to decrease due to the thick surface moraine consisting of volcanogenic material. Comparison of data from the Glacier Inventory of the USSR (as of the 1950s–70s) and the Glacier Inventory of Russia (2017–2019) shows a decrease in glaciation area from the mid-20th century to the end of the second decade of the 21st century in all mountainous regions of Russia except only the volcanic regions of Kamchatka. The area reduction ranges from 63% (Ural) to 13% (Kodar). The largest glacial systems of the Caucasus, Kamchatka and Altai have reduced their areas by 25, 22 and 39%, respectively

The objectives of this study were to analyze satellite data on the ice conditions in the White Sea available for the period 1979-2021 so that to identify statistically significant trends in closeness of ice during that period, and to establish spatial and temporal characteristics of the sea ice regime in this area. It was found that according to the satellite data a statistically significant negative trend (-0.34±0.11% year-1 at a significance level of 0.05) of the ice closeness changes was observed over the above period for all areas of the sea, which corresponds to the general tendency of reducing the area of the Arctic ice cover due to the global warming. However, contrary to the statements of J.C. Comiso, D.K. Perovich, M.C. Serreze, J. Streve, D. Notz that since the beginning of the XX century the reduction of the ice area in the Arctic Ocean accelerates, no tendency in decrease of mean annual values of the ice closeness for the White Sea was revealed. In addition, the results of the regression analysis showed a slight decrease in the absolute value of the trend from - 0.74±0.38% year-1 in 1979-1996 to -0.47±0.25% year-1 in 1997-2020. It is also shown that the results of a comparative analysis of two trends in the year-to-year variability of ice closeness in the White Sea: the first one obtained from the microwave radiometer data provided by the National Snow and Ice Data Center, and the second one revealed from data of advanced microwave scanning radiometers (the University of Bremen), are in good agreement with each other. The difference in the slope coefficients of the linear approximation is only 0.038% year-1 for the period 2002-2020. This is the important argument in support of using microwave radiometer data to determine trends in variability of ice closeness in the White Sea.

Dendrochronology, and lichenometry were used to determine the relative and absolute age of the Late Holocene moraines of the glaciers of the Aktru, Maashei and Shavla valleys (North Chuya ridge, Central Altai). An array of 86dendrochronological dates, related to moraine deposits, is analyzed, 30 of which are published for the first time. Also, for the first time, data on the relative (lichenometric) age of the young deposits of the Aktru Valley, and data on the lichenometry of the moraines of the Maashey glacier and one of the glaciers of the Shavly valley were obtained. We used the capabilities of each method and the expediency of their combined use in the study area. It was confirmed that the growth rates of lichens on the moraines of the Aktru stage (XVIII–XIX centuries) are generally consistent with the previously published estimates. The moraines of the Historical stage, which date earlier than 1700–2300 years ago, supports the lichens as large as 120–160 mm, but the scattering of their diameters is too large and the assessment of the lichenometric ages of these moraines seems to be problematic, but not completely excluded. The Akkem stage of glacier advance according to the recent publications dates back to the Late Glacial or Early Holocene time; the lichenometry is obviously not applicably at such ancient surfaces. According to dendrochronological dating, the glaciers of the North Chuisky Ridge in the last millennium advanced at least twice up to their maximum extent in the XVII– early XIX and XII centuries. In the 8th century, the sizes of the glaciers possibly, approached modern ones. Aſter the XVII century, the cedar (Pinus Sibirica) in Central Altai significantly reduced its distribution area due to the climate cooling, retreating from the periglacial territories, where it was distributed earlier. All trees that grew near the glaciers, above 2300 m, died. The comparison of the dates of glacier advances in the past millennia with the tree-ring, ice-core, and palynological reconstructions of summer temperature and precipitation show a good correspondence.