Vol 65, No 4 (2025)

The mountain ranges surrounding the Central Siberian Plateau host predominantly small-scale glaciation, including minor glaciers and snow-ice formations (SIFs). This study presents updated glacial extent mapping using Sentinel-2 imagery for three regions: the Kuznetsky Alatau (current focus), Baikal Ranges (Baikalsky, Barguzin, and Verkhnenagarsky ridges), and Byranga Mountains (Taimyr). Since the 1960s (Byranga/Baikal) and 1980s (Kuznetsky Alatau), these regions have experienced 50–75% ice loss, strongly correlated with climatic shifts. In the Kuznetsky Alatau (glaciers located at 1.200–1.500 m asl), August 2021/23 Sentinel-2 imagery revealed 78 glaciers (53 previously cataloged in the USSR Glacier Inventory) and 57 SIFs. Slope-attached glaciers showed the most pronounced retreat, followed by cirque types. Satellite-derived parameters were field-verified during August 2024 expeditions. Key characteristics of Kuznetsky Alatau’s cryospheric features include: minimal dimensions, low median elevation, and high meteorological sensitivity (winter precipitation, summer temperatures, wind regimes). Interannual variability reveals both negative mass balance (warming/reduced snowfall) and episodic gains (wind-driven snow redistribution, avalanche deposition, or cooler summers). Using archived Corona (1960) and Hexagon (1973) images, we evaluated discrepancies between the USSR Glacier Inventory (1970s) and satellite-derived glacier areas/altitudes for two glacial clusters in Kuznetsky Alatau. Glacier-climate relationships were quantified using ERA5-Land reanalysis data (temperature/precipitation trends), with comparative analysis against Byranga and Baikal regions.

The formation of runoff is a multifactorial process which is revealed in different ways under the influence of natural and climatic conditions. This is particularly evident in conditions of the high heterogeneity characteristic of mountain-glacial basins. Measurements of glacier runoff do not allow for full control of glaciological monitoring data, but they make it possible to understand better the physical processes that connect local meteorological conditions and ice melting. Hydrological observations during the summers of 2022 and 2023 demonstrated that the runoff hydrograph from the Leviy Aktru Glacier is primarily formed by liquid precipitation and glacier ablation over the previous 48 hours. To extend the series of mean summer temperatures and precipitation totals, constraint equations were applied using data from the Aktru–Goluboe Ozero weather station (operational since August 2019) and the Kara-Tyurek meteorological station. Based on the obtained dependencies, the series of water flow from the Leviy Aktru glacier in June–August was extended, and the gaps in the observations of ablation were restored. A comparative analysis of the restored and measured values revealed that the calculated dependencies overestimate the values of ablation in years with lower summer temperatures, which are characterized by summer snowfalls. According to the Kara-Tyurek weather station, the critical average summer temperature above which the probability of snowfall decreases and the intensity of melting of the Leviy Aktru glacier increases is +5.8 °C.

A study of the chemical composition of snow at the oil fields of Khanty-Mansi Autonomous Okrug – Yugra (KhMAO – Yugra) was carried out from 2015 to 2023. The snow pH and total contents of heavy metals (Cr, Fe, Mn, Ni, Pb, Zn), ammonium and nitrate nitrogen, petroleum hydrocarbons, chlorides, and sulfates were analyzed using data of the environmental monitoring. The content of ammonium nitrogen in the snow corresponded to the background concentration, while the same of nitrate nitrogen exceeded the background magnitudes. A certain acidification of precipitation was revealed. In some sites, pollution of the snowmelt waters with petroleum hydrocarbons was found. Zn and Cr are the most commonly found heavy metals. To identify sources of pollution, a correlation analysis was conducted, establishing a relationship between snow composition and specific indices of technogenesis. The pH value of snowmelt water is in negative correlation with a number of flares used for burning associated petroleum gas. A weak positive correlation was identified between the content of petroleum hydrocarbons and pipeline accident rates. The content of Zn depends on the amount of drilling waste and is determined by the intensity of drilling operations. It was concluded that the composition of snow has a pronounced effect upon the ecological state of surface waters since melting of snow increases the content of nitrate nitrogen as well as the concentration of petroleum hydrocarbons. To determine the trends of atmospheric pollution, the monitoring results of 2015–2023 were compared with the data of 2005–2010. A decline in the concentrations of chlorides, sulfates, nitrates, petroleum products, and iron in the snow was found, which can be attributed to reduction of the volume of associated petroleum gas burned in flares and a lowering of the pipeline accidents.

The article presents results of comparison of the ERA5-Land reanalysis data with results of direct (in situ) measurements of snow depth and the solid precipitation in the permafrost zone in the Magadan Region (Northeast Russia). The analysis was based on daily observations of 21 weather stations (9–850 m a.s.l., 2010–2024) and the authors’ data from 12 stationary snow measuring stakes installed at thermometric boreholes of the regional permafrost monitoring network (175–1182 m a.s.l., 2022–2024). The snow depth on the stakes was recorded at a given time interval using camera traps. The ERA5-Land grid nodes closest to the observation sites with a spatial resolution of 0.1°× 0.1° (~9 km) were used for the comparison with regard for differences in elevation between grid cells and observation sites. The results indicate that the ERA5-Land reanalysis systematically overestimates snow depth (on the average by 27 cm or 168%) and solid precipitation (on average by 6 mm or 113% for the period October–April) compared to in situ measurements. The average correlation coefficient between reanalysis data and observations is 0.73 for snow depth and 0.84 for solid precipitation. Divergence increases in mountainous areas and for stations located on the coast of the Sea of Okhotsk. The dependence of the overestimation of snow depth on the elevation of the observation point was revealed. Thus, the overestimation of snow depth reproduced from the reanalysis data increases up to an absolute elevation of about 500 m, but on levels higher 500 m, this dependence changes to the opposite. ERA5-Land shows earlier snow cover formation and later melting in comparison with observations. In addition to the overestimation of solid precipitation, further sources of uncertainties are the low spatial resolution of the ERA5-Land data and the lack of consideration of sublimation and wind-driven snow transport in the model. The findings contribute to a better understanding of the capabilities and limitations of using the ERA5-Land data in the mountainous permafrost regions.

The purpose of the work is to determine the degree of change in the thermophysical characteristics of the snow cover during compaction. A new indicator, the “snow cover compaction coefficient”, has been introduced. The dependences of the change in the main characteristics of the snow cover on the compaction coefficient have been obtained. The change in the following characteristics has been considered: thermal conductivity, thermal diffusivity, thermal resistance, thermal inertia, thermal stability, and the Fourier and Stefan criteria. A summary table has been constructed, which makes it possible to determine the form of relationship between the above main characteristics and the compaction factor. It has been established that the form of functional relationship between the thermal conductivity coefficient and the snow density plays a crucial role in the quantitative relationship between the characteristics and the compaction factor. For example, if we assume a linear relationship between the thermal conductivity coefficient and the density, the degree of reduction in thermal resistance during snow reclamation is proportional to the square of the compaction factor, while if we assume a parabolic relationship between the thermal conductivity coefficient and the density, the degree of reduction in thermal resistance is proportional to the third power of the compaction factor. The values of the considered thermophysical parameters are obtained from the compaction factor for the case of the dependence of the thermal conductivity coefficient λ on the snow density ρ in the form of a truncated polynomial of an arbitrary degree n. Graphical dependencies of individual indicators on the form of initial functional relationships of the initial values obtained theoretically and from experimental studies and field observations are presented. It is also shown that the percentage discrepancy in the calculation results caused by the choice of exponential function of the thermal conductivity coefficient on density increases for almost all of the thermal properties with an increase in the value of the compaction coefficient and considerably exceeds the value allowed in engineering calculations. For example, the discrepancy of thermal resistance of snow cover when the compaction coefficient is 2.0 is 50 %, and with compaction coefficient equal to 4.0 it is 75 %. The main quantitative relationships of change in thermal conductivity coefficients of snow and thermal resistance of snow cover depending on the compaction degree has been formulated.

In small and medium-sized rivers of the permafrost zone, ice formation lasts for most of the year, and the ice cover often grows to the bottom along the entire length or in some of its sections. However, its impact on the morphology and dynamics of the riverbed, runoff, sediment, dissolved substances, and surrounding deposits is still unexplored. Observations on the formation and destruction of ice cover, freezing and thawing of riverbed sediments, and water turbidity on three small and medium-sized rivers were made in Central Yakutia. The data obtained from hydrographic stations of the Yakutsk Hydromet Office in 2008–2022 were used for our analysis. The character of the river’s freezing, whether the ice cover grows to the bottom along the entire length or the river or only in certain areas, depends on its morphology. Even in the absence of water sources in winter, lenses of unfrozen water still remain in the deepest (more than 1.5 m) sections of rivers, such as pools of beaded channels or meandering rivers. Local tallks up to 4 m thick are preserved under sections of the river with floating ice, while under sections of the rivers with bedfast ice, the sediments completely freeze in winter. On rivers with bedfast ice a significant part of the snowmelt runoff passes over the ice cover. The presence of ice in the riverbed promotes rising of water levels and increased water flow rates, but at the same time, it protects the sediments on the bottom and banks of the river from thawing and subsequent erosion. The peak of water discharges during the spring flood on the smallest rivers passes over the ice; but as the size of the river increases, the peak of water discharge shifts to later dates, so it occurs on the ice-free riverbed. Thus, the effect of spring floods on the erosion of the bed and banks of rivers with bedfast ice is reduced due to the energy expenditure of the water stream in the first phase of the flood on the destruction of ice filling the channel and the thawing of the bed and banks material. This phenomenon is more pronounced on the smallest rivers, which have lower thermal energy, than on larger ones.

The results of a study of the long-term climatic changes in the “surface air – soil” system to a depth of 3.2 m in the western section of the Baikal-Amur Mainline (BAM) railway are discussed. The monthly average minimum and maximum ground temperatures and characteristics of seasonal freezing and thawing are considered. There are clear regional differences in climatic conditions for the two groups of weather stations. The first group (Lena-Angara plateau and Pre-Baikal depression) is characterized by moderate winter cooling and summer warming in soils with positive mean annual temperature. The type of permafrost thermal regime is long-term seasonal freezing. The second group (Stanovoy Upland basins) is characterized by both moderate (isolated cases) and strong winter cooling in soils. Deep (more than 3.2 м) seasonal freezing prevails, which in some landscapes merges with permafrost. In summer, the ground warming is moderate and weak. Very weak warming is characterized by thawing only to a certain depth. In most basins, the mean annual temperature is negative throughout the soil profile. The types of permafrost thermal regime in the basins are long-term and deeply seasonally frozen type. Current changes in the climate indicators of the surface air and soil have been identified. Their good consistency has been noted. Positive linear trends in precipitation, air and soil temperatures have been recorded. The BAM region shows significant warming, especially in winter.

This review provides the present-day assessment of natural environment state of the Svalbard Archipelago in the first quarter of the 21st century. In recent decades, the region was subjected to significant environmental changes due to fast climate warming associated with the Arctic amplification, when rates of the surface temperature growth exceeded the global means by several times. This resulted in marked transformation of the local ecosystems. The key environmental factors, including (1) climate, (2) oceanography, (3) sea ice, are considered in the first part of the article. The paper presents current trends in surface air temperature and sea ice, as well as the dynamics of Atlantic Water inflow into the archipelago's fjords. Although Svalbard is among the most accessible and thoroughly studied regions of the Arctic, there are significant gaps in knowledge due to technical and methodological difficulties. The problems involve fragmented and incorrect data on the atmospheric precipitation, a lack of year-round oceanographic observations, and insufficient understanding of the impacts of Atlantic water on the fjords. These aspects open ways for future research, with a particular emphasis on interdisciplinary approaches that may enhance understanding of ecosystem changes in the context of climate change.

During the summer expedition 2025, glacio-climatic observations were carried out on the Levyi Aktru glacier, which marked the beginning of permanent monitoring. Assessments of the glaciological parameters of the Levyi Aktru and Vodopadny glaciers were also carried out using geodetic methods. Interesting features of the altitude distribution of snow accumulation were revealed, and the contribution of summer snowfalls to the variation of the glacier radiation regime during ablation period was noted. Spectral analysis of data series revealed a significant role of mountain-valley circulation in the formation of the thermal regime over the glacier surface, as well as the influence of synoptic variability on the cloudiness regime and the course of relative humidity over the glacier. The obtained data are necessary to identify the mechanisms of Altai deglaciation, assess the glacial component of runoff, and verify models of glacial systems. In particular, calculations of the variability of the main glaciological parameters using the Oerlemans minimal model using measured mass balance characteristics (1977–2012) showed that the Levyi Aktru glacier can be used as a model object.