The bays of northern Fennoscandia boast the most developed port infrastructure in the Arctic. Due to climate warming, the bays of northern Scandinavia and the Kola Peninsula hold enormous potential for logistics in the further development of the high latitudes. Understanding the processes and the future trends of sedimentation in individual basins is of fundamental and applied importance. Based on radioisotope dating (210Pb, 137Cs) of bottom sediments from four bays (Vefsnfjord, Malangenfjord, Yarnyshnaya Bay, and Oscar Bay), linear sedimentation rates (SAR) and mass (MAR) accumulation rates over the past century were estimated. Climate trends (Tromsø, Murmansk), the influence of the cryosphere, catchment geomorphology, and anthropogenic factors were analyzed. A relationship between sedimentation rates and temperature was found in all the basins, but the nature of the response varied. In general, the bays of northern Fennoscandia, whose catchments are not subject to glaciation or permafrost, exhibit a consistent range of sedimentation rates (SAR ≤ 0.27 cm/yr, MAR ≤ 0.26 g·cm⁻²·yr⁻¹). In Malangenfjorden, where the catchment contains actively degrading glaciers and permafrost, the SAR increased by a factor of 7.6, reaching 0.38 cm/yr, exceeding the regional sedimentation range. In Vefsnfjorden, where the catchment is not glaciated, the increase did not exceed 2.5 times (primarily anthropogenic erosion). The bays of the Kola Peninsula showed changes of 2.2-fold changes, with the peaks synchronous with the temperature maxima, and remained within the regional sedimentation range. Bays that do not have a perennial cryosphere in their catchment area maintain stable rates of sediment accumulation within a range of values and are relatively resistant to silting under conditions of rising temperatures in the Arctic. Fjords with an actively degrading perennial cryosphere may require enhanced monitoring and revision of dredging regulations in various parts of the basin.

Information on air temperature and precipitation, often necessary for runoff modeling and forecasting, cannot always be obtained from ground-based observations. Therefore, the problem of selecting a source of climate data that is continuous in space and time becomes urgent. This paper evaluates the accuracy of 7 air temperature and 13 precipitation datasets for the Lena River basin in comparison with ground-based observations. For time series of average annual and seasonal air temperature and precipitation from 43 weather stations and climate products under consideration, the Pearson correlation coefficients, Root Mean Squared Error (RMSE), Kling–Gupta efficiency (KGE’) were calculated for two time periods: 1950–2024 and 1980–2024 for air temperature, 1966–2020 and 1982–2020 for precipitation. Correlation coefficients (average for the stations under consideration) with annual and seasonal mean air temperatures for 1980–2024, calculated from meteorological station observations, were found to range from 0.75 to 0.98 for all the products, while average RMSE ranged from 0.6 (GHCN CAMS) to 1.1 °C (NCEP-NCAR and NCEP/DOE Reanalysis) for annual mean temperatures. Climate products such as GHCN CAMS, JRA-3Q, ERA5-Land performed better than the others in reproducing air temperatures for both time periods. In the case of precipitation products, for the period 1982–2020 average correlation coefficients with ground-based observations ranged from 0.49 to 1.00, RMSE of annual precipitation totals was from 7 to 203 mm (the best results shown by GPCC Full Data Monthly Product, the worst — by NCEP-NCAR and NCEP/DOE reanalysis). For the period 1982–2020 the GPCC Full Data Monthly Product (KGE’ for annual precipitation = 0.97), GPCC Monitoring Product (KGE’ 0.84), CPC-Global (KGE’ 0.83) datasets showed the best agreement with the ground-based observations. For the period 1966–2020, the best performance was shown by the GPCC Full Data Monthly Product, PREC/L, and data downscaled from CRU TS4.09 with WorldClim 2.1.

To identify the relationships between gully dynamics, snowmelt, soil thaw, runoff of water, sediment, and dissolved solids, observations were conducted during a snowmelt in a small catchment near the Tiksi settlement (Arctic Siberia). At the onset of the flood, snow filling the gully impedes water runoff, slowing the thawing of the gully sides and sediment supply to the watercourse. The shallow depth of soil thaw facilitates the concentration of surface flow in hollows, the growth of the narrow gully head, and the erosion of the bed. After the snow has melted from the catchment area and the flood peak has passed, the snow remaining in the gully becomes the main source of stream water, reducing mineralization and cooling of the water. Less than half of the suspended sediment passing through the gully mouth originated within the gully itself; most of it was transported from the catchment area. About 30 % of the removed sediment was deposited immediately downstream of the gully. Suspended organic matter accounted for approximately 14 % of the total suspended sediment discharge during the flood. Over 95 % of the dissolved solids discharge is generated in the catchment area and is determined by processes occurring there; only 5 % comes from the gully itself. The chemical composition of the stream water changes as snow melts and the soil in the catchment thaws. Calcium, magnesium, sodium, and sulfate ions are elevated at the very beginning of snowmelt; their concentrations decrease with increasing water flow, and then begin to increase again with soil thawing. Potassium and chloride ions have maximum concentrations at the beginning of the flow, which then decline. Bicarbonate and ammonium ions show no discernible trend. The active influx of sediment and organic matter released by intensified erosion due to permafrost degradation is limited by the frozen state of the sediments and snow filling the gully at the onset of the flood, and by the insufficient transport capacity of the stream during the subsequent warm period, leading to their accumulation. This inhibits downstream sediment transport under conditions of intensified exogenous processes driven by climate change.

Glacier mass balance is widely used as an indicator of climate change; however, long-term mass-balance records may reflect not only climatic forcing but also a “geometric” signal associated with changes in glacier hypsometry and spatial configuration. In view of the accelerated glacier retreat observed over recent decades, this effect becomes increasingly important. This study quantifies the contribution of geometric changes to the mass balance of two valley glaciers on the Svalbard archipelago — Aldegondabreen and Vestre Grønfjordbreen — where continuous glaciological monitoring has been conducted since the early 21st century. Using elevation data combined with in situ mass-balance measurements, specific mass balance was calculated using two approaches: with a fixed reference surface and with annually updated area–altitudinal distributions. Geometric changes lead to additional mass losses of 0.02–0.04 m w. e. yr⁻¹ for Aldegondabreen, and only of 0.01–0.02 for Vestre Grønfjordbreen. This effect is positive geometric feedback: as the glacier loses mass, its surface becomes less elevated, thus enhancing future mass loss. For both glaciers, the “purely climatic” mass-balance trend does not differ significantly from the observed trend, equaling –0.09 ± 0.03 m w. e. yr⁻¹ for Aldegondabreen and –0.13 ± 0.04 m w. e. for Vestre Grønfjordbreen (α = 0.05). These findings indicate that neglecting glacier geometry evolution can bias interpretations of mass-balance time series and associated climate signals. Repeating similar analyses across different glacier types and regions is essential for assessing the magnitude and significance of the geometric signal in diverse glaciated environments.

Against the backdrop of the reindeer herding crisis in many Arctic regions, the dynamics of its development in the north of Western Siberia are an exception. Over the past decade of the 20th century and the beginning of the 21st century, the territory of its largest reindeer herding center, the Yamalo-Nenets Autonomous Okrug of the Tyumen Region, has seen an increase in the number of reindeer, which currently accounts for about a third of the global total. Therefore this region can be considered a unique model territory which allows us to assess the nature of socio-natural interactions related to reindeer herding in their most intense form. In the historical retrospective, the paper examines the features of socio-natural interactions related to the regulation of the load on pasture lands in reindeer herding in the Yamalo-Nenets Autonomous Okrug. The study is based on the analysis of literature, archival sources, and the generalization of the authors' field research. It has been established that during the period from the second half of the 19th century to the beginning of the Soviet era, the traditional forms of regulating the number of reindeer and their grazing routes contributed to the preservation of a high potential for the regeneration of pasture lands. During the Soviet period, conditions gradually emerged for overgrazing of reindeer, and by the 1960s, it had become a problem in the Yamal and Priural districts. Since the 1990s, overgrazing of reindeer has become a serious issue. As to the causes of the problem, it has been established that the major factors are the reduction of grazing routes and an increase in the number of the herds against the background of the reduction of the land in the process of developing the infrastructure of the oil and gas production complex. Economic processes play a crucial role as factors that transform the Arctic ecosystems. The increasing irreversible negative consequences of overgrazing on the ecosystems could critically increase the vulnerability of reindeer herding. In this situation, it is necessary to develop new approaches to regulating reindeer herding based on achieving a reasonable balance between the development of its commercial functions and its impact on the Arctic ecosystems.

In modern paleoecological research, subrecent (modern or near-modern) data are the basis for constructing calibration models that allow us to interpret the fossil records. Therefore, it is important to understand how accurately subrecent data reflect the composition and structure of modern plant communities, especially in areas where vegetation distribution is highly dependent on topography, local microclimate, and regional climatic parameters. The article presents the results of a comprehensive study into the composition of 17 surface samples collected in plant communities of the Malozemelskaya tundra within the vicinity of Lake Golodnaya Guba. Surface samples were collected from both typical zonal shrub/dwarf-shrub moss tundra and extra-zonal spruce and birch forest areas that are atypical for tundra. The samples were studied using pollen and plant macrofossil analyses. Our data show that the subrecent pollen spectra and macro-remain complexes as a whole reliably reflect the composition of shrub tundra plant communities, characterizing the zonal and local components. However, the degree of participation of individual plant species does not always correspond to their role in communities. The subrecent pollen spectra and macro-remain complexes of the extrazonal forest stands are similar to those of the forest-tundra, reflecting the forest type of vegetation. Spruce and birch pollen does not show a significant deformation on zonal subrecent pollen spectra. Macrofossils of these tree species were found only sporadically outside extrazonal forest areas. The presence of pine pollen, as a long-distance component, does not have a significant effect on the subrecent spectra. Macro-remains of pine were not found in subrecent complexes. The adequacy of subrecent pollen spectra and macro-remain complexes to plant communities is confirmed by cluster analysis, according to which the most statistically similar spectra and complexes are formed in phytocenoses with similar floral composition. The revealed patterns and features of plant communities composition as reflected in subrecent spectra and complexes will enable more accurate paleo-ecological reconstructions within the Malozemelskaya tundra based on pollen and plant macrofossil analyses.

Blagopoluchiya Bay (the Solovetsky Archipelago, White Sea) is a recipient of wastewater from the Solovetsky settlement and is susceptible to pollution by nutrients and organic matter. Anthropogenic impact leads to decreasing of the recreational value of the Bay and deterioration in water quality as a result of intensive growth of green macroalgae, so-called “green tides”. The aim of the work was to assess the environmental situation in the Bay. The aseesment was perfomed on the basis of hydrochemical, hydrobiological and microbiological studies in June and August 2025 during various phases of the tidal cycle. Blagopoluchiya Bay is a relatively shallow area with depths in the northern and southern parts of no more than 2 m, while at the entrance to the bay, the depths reach 8–9 m. The tidal range in the bay varies between 0.5 and 0.7 m. The current velocities at different tidal phases are relatively slow, not exceeding 10–15 cm/s. High concentrations of nutrients (121–1058 μg/L total phosphorus and 1.21–1.58 mg/L total nitrogen), as well as total coliform bacteria (up to 90000 CFU/100 cm³) were detected in the area of the Solovetsky settlement wastewater discharge. The data characterize the sanitary situation as critical. At other stations in Blagopoluchiya Bay, the content of nutrients was 2–20 times lower, and the number of total coliform bacteria was 4–1800 times lower. Despite the high concentrations of total phosphorus, indicating the eutrophic and even hypertrophic status of the Bay, chlorophyll “a” concentrations in the wastewater discharge area were low and corresponded to the mesotrophic level (2.07–3.29 μg/l). At the exit from the bay, the concentrations of chlorophyll “a” corresponded to the oligotrophic level (0.97–2.0 μg/l). This situation is explained by the widespread development of macroalgae in the bay, including representatives of the genus Ulva, which contribute to the formation of “green tides”. Phosphorus content in macroalgae mass at different stations in Blagopoluchiya Bay varied between 0.24–0.36 % (of dry weight). The interception of nutrients by macroalgae results in low concentrations of their mineral forms, which hinders the intensive development of phytoplankton. Consequently, low levels of chlorophyll “a” are observed. The monitoring results indicate an unfavorable environmental situation in Blagopoluchiya Bay, requiring immediate wastewater treatment. An important measure to improve the situation in the Bay is the removal of macroalgae from the areas where they grow.

The severity of the ice conditions and absence of winter maritime operations in the area in the winter season 2024/25 explain the limited understanding of ice navigation conditions in the northwestern and western parts of the Sea of Okhotsk. In 2024, the Port Elga coal terminal was built and the year-round transportation of coal started from the Elga deposit to Cape Manorsky and then to the southern Sea of Okhotsk. In this study we conducted continuous monitoring of the first winter navigation season in the northwestern Sea of Okhotsk. Based on the results, we identified several specific features of the ice navigation conditions. Specifically, ice conditions in certain localized areas became more severe due to dynamic factors and changes in the ice structure during the spring melting period. In the course of the study, we obtained and analyzed information on the characteristics of navigation in an area where there had been no previous permanent winter navigation and determined the position of optimal navigation routes in the northwestern and western regions of the Sea of Okhotsk at various stages of ice formation. The 2024/25 winter-spring navigation was analyzed over several key periods, as ice conditions became more difficult. At the beginning of the season, navigation followed the shortest southern route and was easy for ships with ice class Arc4 or higher. The second period required icebreaker assistance. In the third period, navigation routes shifted northward due to more difficult ice conditions. In the fourth period, icebreaker assistance was provided by two icebreakers simultaneously. In the fifth, most challenging period, ship traffic was almost stopped due to severe ice conditions. The main conclusion of the study is the need for both continuous monitoring of ice conditions and specialized shipboard ice observations to provide timely forecasting of ice conditions, thereby improving the quality of specialized hydrometeorological support for ships during maritime operations.

This paper outlines the history of Russian and Soviet studies on the thermophysics of ice. Although in Europe this science existed as early as the 18th century, first Russian studies on ice thermophysics were conducted only in 1845–1846, in Pulkovo Observatory, by the research team of Academician V. Struve, upon the initiative and with immediate participation of the academician himself. Further studies were carried out in the early 19th century by A. Bogoyavlensky, privat-docent of Yuriev University, who experimentally investigated the heat absorption and melting point of fresh-water ice. Experimental studies on the heat conductivity coefficient of ice were carried out as per novel procedure, and the results were published by S. Artsibashev and I. Parfianovich in 1928. The understanding of sea ice thermophysical behaviour was heavily influenced by a book written by F. Malmgren and published in the year 1930. To elaborate on certain topics of the book, V. Shuleykin and his research team experimentally investigated the effect of ice porosity upon its heat conductivity coefficient. The year 1932 saw the publication of the books by A. Komarovsky and N. Zubov, with data sheets on the physical properties of fresh-water and sea ice. The same years saw vigorous advances in applied ice engineering (in particular, thermophysical processes in ice). These included empirical expressions obtained for predicting ice thickness growth depending on the number of degree-days with cold temperatures, regelation of ice, as well as ice generation in layers for building ice roads and ice depots. On the whole, however, despite its relevance to many practical applications, ice thermophysics as a research field still remained of secondary importance.