Ocean eddies are an important factor in the large-scale dynamics of the global ocean, including   polar and subpolar regions. A robust statistical information on the number and characteristics of mesoscaleand submesoscale eddies will yield new insights on their effect on dynamics of large-scale currents, ice-edgevariability, and other dynamic and biochemical processes in the ocean. Optical images complement the results of the eddy identification study in radar and satellite altimetry images, each of which has its inherent limitations. In optical images, eddies are often observed as spiral or mushroom-shaped structures in chlorophyll distribution, which are formed through the effect of eddy rotation and convergence/divergence patterns. Massive studies of characteristics of ocean eddies require algorithms for their automatic identification. Although several such algorithms have been suggested for satellite altimetry and radar data, no such algorithm exists for satellite optical images. It this study we propose a machine deep learning algorithm for efficient automatic eddy detection in Sentinel-3 optical images. The Lofoten Basin of the Norwegian Sea, an area with a small Rossby deformation radius of less than 10 km, but densely populated with eddies, was selected as a region for algorithm training and validation. Even though the study area is known as one of the cloudiest areas of the northern polar latitudes, 52 mostly cloud-free images were collected over the 9 years of Sentinel-3 data, where 938 eddies were detected. For automatic eddy identification we used SegFormer neural network architecture with an AdamW optimizer, applied for 512×512 pixel tiles. In the course of validation high quality metrics were obtained: Precision = 0.94, Recall = 0.91, Intersection of Union = 0.87 and Dice = 0.93. This demonstrates high efficiency of the algorithm developed. The algorithm additionally identified several eddies missed during visual image inspection. The results of the study are particularly relevant to polar ocean regions, where the predominant eddy sizes are significantly smaller than in the tropics. The robust identification of eddies in optical images is a promising step forward in understanding mesoscale and sub-mesoscale eddy dynamics.

The study presents an analysis of the large-scale spatiotemporal variability of sea surface temperature (SST) in the Atlantic sector of the Arctic, a key region for the transformation of Atlantic waters and heat exchange between the North Atlantic and the Arctic Ocean. To achieve this, the Empirical Orthogonal Function (EOF) decomposition method was applied to the original monthly mean SST anomalies from the ERA5 reanalysis over the period 1950–2024. Three leading modes have been identified, collectively accounting for 55,8 % of the total SST variance. The first mode (25 % of the variance) exhibits a spatial dipole structure, separating the study area into western and eastern parts. It reflects the mechanism of intensified advection of Atlantic waters northward and eastward, correlating with the heat flux through Fram Strait (R = 0.42) and the Arctic Dipole index (R = 0.27). The second mode (16,4 % of the variance) is characterized by a latitude-oriented dipole structure. Its temporal evolution and significant correlation (R = 0.58) with the Atlantic Meridional Overturning Circulation (AMOC) index reflect the influence of low-frequency oceanic variability. The third mode (14,4 % of the variance) exhibits a complex structure with a positive anomaly in the western and central parts of the basin. It   is interpreted by the authors as an indicator of deep convection intensity in the Greenland Sea, a finding supported by its correlation with temperature in the 500–1750 m layer (R = –0.48). It is established that the spatial structures identified are formed under the combined influence of advective heat transport by Atlantic waters, multi-decadal variability in the intensity of the AMOC, and atmospheric circulation patterns associated with the Arctic Dipole and the Arctic Oscillation. The results obtained quantitatively determine the contribution of the leading modes to the total SST variability in the Atlantic sector of the Arctic, which is essential for understanding the regional climate response to global changes and for refining the mechanisms of Arctic amplification.

The “Warm Arctic — Cold Eurasia” (WACE) pattern is a manifestation of Arctic amplification's influence on mid-latitude climate. Despite extensive research, crucial aspects such as its intraseasonal dynamics and the precise role of atmospheric blocking remain highly debated. This study presents a comprehensive analysis of the spatiotemporal variability of the WACE pattern and its connection to blocking anticyclones using ERA5 reanalysis data (1979–2023) on a 2.5° × 2.5° grid. We employed two independent methods to calculate the WACE index — based on temperature anomaly differences between the Barents-Kara Seas (BKS) and Central Eurasia (CE) and via Empirical Orthogonal Function (EOF) analysis, which objectively identified the WACE pattern as the second leading mode of temperature variability, explaining ~17 % of the variance. Atmospheric blocking was diagnosed using the GHGS index at the 500 hPa level, distinguishing between northern (50–70° N) and southern (40–60° N) regimes to account for the seasonal shifts in the blocking latitude. Our analysis reveals a sustained restructuring of atmospheric circulation since the early 2000s, marked by a statistically significant intensification of the WACE pattern in the autumn-winter period (a trend of 1.4 °C per decade for December-February) and a fundamental shift in its seasonal progression. It has been found that in the early cold season (October–November), the WACE pattern is most strongly correlated with the northern blocking events. The longitudinal focus of this correlation has shifted eastward, with its peak located over the Western Siberian sector (70–90° E), rather than the traditional Ural Mountains. The correlation coefficients in this sector for the northern regime reach 0.7 in October, underscoring a robust linkage. This points to a transformation of the primary mechanism behind WACE formation after the year 2000, which is now governed by high-latitude blocking over the increasingly ice-free Kara Sea. The observed systemic shift towards high-latitude, “Rex”-type dipole blocks effectively shortens the transitional autumn period, leading to an earlier and more abrupt establishment of winter-like circulation. These findings are important for understanding fundamental changes in seasonal circulation over Eurasia and for improving the predictability of extreme cold weather events.

We present an analysis of ten-year (2015–2025) in situ measurements of shortwave downward radiation (SWD) near Barentsburg, Spitzbergen. The measurements were performed using an automatic weather station near the Aldegondabreen Glacier at 180 m a. s. l., equipped with a Hobo silicon pyranometer (300–1100 nm, ±5 % accuracy). The actual maximum radiation occurs between 15 May and 25 June, preceding the theoretical peak of the astronomical cycle, with a mean daily flux of 204 W m–², then gradually decreasing after late June. The data collected show good agreement with Ny-Ålesund measurements (R² = 0.83) and ERA5 reanalysis data (R² = 0.89). According to the latter, during the melt season a negative trend in shortwave flux has been observed since at least 1960, with –3.3 W m–² per decade over 1976–2024, and a sudden decrease occurred in the late 1970s, likely linked to increased cloudiness from reduced sea ice. A comparison of the two climatic normals shows that the decrease in incoming shortwave radiation is seasonally uneven. It is limited to late summer, when radiation levels are already low, whereas in May and early June — during the seasonal maximum — no reduction is evident. Consequently, the timing of snow cover disappearance is a key control on glacier melt as maintaining a high surface albedo in early summer is critical for limiting melt. Quantitative assessment shows that a two-week shift in snowmelt timing changes the solar radiation absorbed by glaciers by ~111 MJ m–², which is an equivalent of 0.36 m w. e. of glacier melt.

The increase in freight traffic along the Yana River due to the expansion of mining in the basin, the development of settlements, transport and energy infrastructure requires the updating of information about the current hydrological regime of the Yana River as the region's main transport route, the source of water and hydrological hazards. Based on new hydrological data, the characteristics of annual water runoff and ice regime, maximum and minimum flow rates and water levels have been clarified, analysis has been carried out of their long-term fluctuations including the determination of the magnitude and sign of changes, cycles of water content, turning years, and the contribution made to these trends by the main tributaries of the Yana, the parameters of the curves of probability distribution functions have been calculated. It is found that the average annual, maximum and minimum water discharges in the lower reaches of the Yana River increased by 24, 12 and 36 %. The increase in the annual water flow of the Yana River ensured positive trends in all the hydrological seasons and by all the rivers of the basin. The main turning points were 1989, 1996 and 2004. Of all the maximum discharges, the largest increase was observed for the maximum spring flood discharges (+22 %). Changes in water runoff have affected the level regime of the lower Yana, flood characteristics, and navigation conditions. Disturbances to the ice regime were considered minor. It is found that the frequency and parameters of floodplain flooding have increased everywhere (since the mid-1990s), primarily due to an increase in the maximum levels by an average of 0.2–0.5 m. As a result, since the 1990s, two catastrophic, four large and five small inundations have been recorded, five of which occurred in the lower reaches of the Yana River. Since 2008 and throughout 2018, navigation conditions have deteriorated, particularly at the Yana River mouth bar. Combined with the flooding, this significantly increases the costs of preventing and mitigating hydrological hazards and hinders the region's socioeconomic development.

Climate conditions largely control the properties and distribution of permafrost. Its sensitivity to warming makes it a valuable indicator of ongoing climate change. This is especially true for High Latitudes, where climate warming accelerates at the highest rates worldwide. However, little is known about permafrost conditions, its properties and features on the High Arctic Islands, the northernmost land where permafrost occurs. For the first time, the present study summarizes Soviet literature data, recent drilling and other observation data of periglacial landforms, ground temperatures, cryostratigraphy and ground ice properties (including stable water isotope data, partly obtained during the Arctic Century Expedition in 2021) on the Severnaya Zemlya Archipelago and adjacent Wiese Island in the Russian High Arctic. The study provides baseline information on High Arctic permafrost to encourage and promote further investigations of the state and dynamics of warming permafrost.

Two types of frozen bogs, palsa mires and polygonal marshes, occupy up to 30 % of the permafrost terrain in West Siberia. Palsa mires span the territory from the Arctic Circle down to approximately 62° N in continuous, discontinuous and sporadic permafrost zones; polygonal marshes are located northward from the Arctic Circle. The hydro-thermal regime of permafrost bogs is characterized by three key parameters, namely, soil temperature, active-layer thickness (ALT), and soil water table depth. We used the CryoGrid community model with daily ERA-5 reanalysis meteorological data to study changes in these parameters in the period 1971–2024. The model was calibrated using an extensive historical data set of the State Hydrological Institute for 10 permafrost bog plots, which was built up in the course of the field expeditions in West Siberia in the 1971–1992 period. The calibrated CryoGrid model demonstrated reasonably good performance in reproducing observed parameters of the hydro-thermal regime of permafrost bogs in a variety of climatic, bio-physiographic and permafrost conditions. The mean square errors of the calculated parameters for polygonal marshes/palsa mires were the following:   ALT error (3.8 ÷ 5.6 cm)/(5.2 ÷ 5.9 cm); soil temperature error (1.2 ÷ 1.5 °C)/(0.8 ÷ 1.3 °C) and soil water level error (6.8 ÷ 10.5 cm)/(7.9 ÷ 9.7 cm). The modelling results suggest that changes in the hydro-thermal regime of permafrost bogs have increased in the past 25 years. Calculated over the 2000–2024 period trends, averaged over the areas occupied by polygonal marshes and palsas, were, correspondingly, as follows: 1.35 and 1.10 °С/10y for soil temperature at 20 cm depth; 9.6 and 5.2 cm/10y for ALT; –1,1 and –2,9 cm/10y for soil water levels.

Sea ice leads are narrow linear-shaped openings enclosed in ice. They may be covered with nilas or young ice. Climatological values of modal lead orientation and specific lead length are important characteristics for the study of spatial and temporal variability of leads both for needs of navigation in the Arctic and in the context of the Arctic climate change. To calculate climatological lead characteristics, a long-period data archive is required. The main source of observations on leads is satellite imagery. Manual interpretation of leads in satellite images is an extremely labor-intensive process. In 2025, we developed a method for automatic identification of leads retrieved from SuomiNPP infrared satellite images using a convolutional neural network. As a result of image processing with this method, each lead is represented as a polyline and defined by a set of geographic coordinates for the ends of the line segments. This kind of data representation provides calculation of all the main lead characteristics. Using the method, we compiled a data archive on leads in the Laptev and East Siberian Seas for 2012–2025. Data on leads for spring months were derived from visible-range SuomiNPP (for April–May 2012–2025) and Terra (for March–May 2000–2011) images. For this type of images, the model was retrained. The results obtained were verified by comparing the modal orientation and specific length of leads calculated from automatically identified data with those from expert interpretation data. It was found that the difference in modal orientation of leads was minor in a vast majority of cases: the average difference was 7–8°. Differences in the specific lead length were also small, averaging 1–10 m/km2. Data on leads in the winter months of 2000–2011 were retrieved from the free available results of processing the MODIS ice surface temperature data by applying the “multiway” algorithm, which is part of our method for automatic identification of leads. Verification of the results obtained in this way showed that the average difference in modal orientation values was 11°. Therefore, using lead data from all the datasets produced will not introduce significant error in the subsequent determination of generalized lead characteristics, provided that differences in the spatial resolution are taken into account. This enables us to aggregate all the datasets produced into a single data archive on leads in the Laptev and East Siberian seas in 2000–2025.

Human activity and settlement development in the high Arctic impact the functioning of natural ecosystems, including bird ecology. The study examines the nesting dynamics of six bird species in the Russian settlement of Barentsburg (Spitsbergen archipelago) in the 21st century. The settlement reconstruction, carried out since 2010, has affected the distribution of glaucous gulls, black-legged kittiwakes and snow buntings. In Barentsburg, the glaucous gull breeds successfully on the roofs of buildings with varying numbers of storeys. A subcolony of this species relocated to an industrial habitat (the retaining wall of a coal yard) in 2025. This was due to the dismantling of a utility box where 2–4 pairs of glaucous gulls had been recorded nesting annually for many years. Several black-legged kittiwake subcolonies on some buildings in the center of the settlement disappeared after reconstruction. One large colony (280 pairs) formed on a thermal power plant building on the outskirts of the settlement. This is due to the demolition and reconstruction of some buildings, as well as measures that prevented nesting on windowsills. The snow bunting population has decreased by a third in the settlement: from 40–50 pairs in 2004 to 25–35 pairs in 2025. This is due to the cladding of brick buildings with panels and siding, the closing of ventilation niches, the liquidation of subsidiary farms, the demolition of utility boxes, and competition with common guillemots for nesting niches on buildings. The Arctic tern colony near the helipad area has changed its location, moving entirely to the rooftops of buildings, increasing its population from 20 pairs in 2001 to 60 pairs in 2025. Nesting on tall buildings and structures allows them to avoid predation by Arctic foxes. A rapid expansion of common guillemots into industrial and residential habitats has occurred in the last decade: from 3–4 pairs in 2016 to 13–14 pairs in 2025. The common guillemot has completely displaced the snow bunting on one of the buildings and formed a nesting colony of 8 pairs. This likely occurred due to an influx of individuals from the cliff colony closest to the settlement, where the numbers of this species had declined. This event is not related to the settlement's reconstruction. Nesting of the ringed plover has been recorded directly on the helipad. Thus, in the 21st century, changes have occurred in the numbers and nesting patterns of most of the species studied due to both the peculiarities of the reconstruction of buildings and structures and other factors.