Water levels exceeding critical values pose a danger to economic facilities located in the adjacent territory. The aim of the work is to obtain, using the materials of the Water Cadastre, the most general characteristics of unfavorable water levels relative to the critical values established by the decision of the UGMS, based on observations at stationary posts in the Ob and Taz Bays. These posts include New Port, Cape Kamenny, Tadibeyakha, Seyakha, Tambey, 60 Let VLKSM, Antipayuta. No generalizations on this issue are found in the research literature for the area under consideration. Sources of initial data are hydrological yearbooks for the Kara Sea basin for the period 1953–2019. The generated series of levels for each post are brought to a single reference plane for the observation period. The length of the rows ranges from 14 to 61 values. As a result of data analysis, the following characteristics of unfavorable levels were obtained: the proportion of years with extreme levels above the critical level during surges and floods and below the critical levels during surges; distribution by month of the largest exceedances of levels above and below the critical ones during the year; the maximum values of exceedances and duration of levels above and below the critical ones; repeatability of values of extreme annual elevations/decreases in level relative to the critical ones at given intervals; information on the maximum number and duration of repeated cases of unfavorable levels at the post per year and the total duration for the entire period. It has been established that among the posts that have a series of observations of levels over 20 years, the most unfavorable conditions in terms of levels are formed for the Tadibeyakha and Antipayuta posts in all indicators. The results obtained can be used in risk assessment depending on the high- altitude location of a structure being designed. They take into account the possible adverse effects of extreme levels on these structures.

The temperature in the Arctic is increasing faster than the global average. A question that challenges scientific community is whether the intensity and frequency of dangerous meteorological phenomena in the Arctic are increasing as rapidly. The article presents the results of examining abnormal summer seasons in the area of the Spitsbergen archipelago. The study used data on surface air temperature in Barentsburg obtained from 1912 to 2023. The regional average results showed a statistically significant linear summer trend. The mean summer temperature in Barentsburg is increasing at a rate of 0.2 °C/10 years. Positive and negative extremes of seasonal mean temperature in the summer from June to September were determined as higher than or equal to 1,5 standard deviation. The atmospheric circulation at the sea level pressure and at the height of the geopotential surface of 500 hPa is analyzed, and the localization of surface temperatures anomalies for highlighted abnormal temperature in summer season events is discussed. The results of the analysis of atmospheric circulation revealed significant differences between abnormal warm and cold summer seasons. During abnormally cold summers the circumpolar vortex is located in the polar region and causes the advection of cold air masses from the north of Greenland. In the case of abnormally warm summers the cyclonic vortex is shifted to the Canadian Arctic archipelago and the Baffin Sea, while warm air masses from the Atlantic Ocean enter the area of the Spitsbergen archipelago. The assessment of the statistical significance of the correlation between the time series of surface air temperature anomalies and the atmospheric circulation indices Arctic Oscillation, Arctic dipole, Pacific North American oscillation showed significant results in September with the Arctic Oscillation index, in August and September with the Arctic dipole index, in July with the Pacific North American oscillation index. The greatest statistically significant association of surface air temperature anomalies was found with the Arctic dipole index, the closeness of the connection in September was –0.49. Spectral analysis was carried out and the main periods of atmospheric indices fluctuations from 2–3 years to 25 years were determined.

The paper presents an assessment of the distribution of riverbed types in homogeneous landscape areas of the Arctic zone located in various permafrost conditions. The Arctic territories of the Komi Republic, the Nenets Autonomous Okrug, Yakutia, the Krasnoyarsk Territory and the Yamalo-Nenets Autonomous Okrug are considered. For the first time, a distribution scheme of riverbed types for the middle rivers of the Russian Arctic regions has been compiled, based on a typification developed for permafrost conditions. The analysis showed that tundra landscapes are characterized by a greater distribution of unlimited alluvial rivers, compared with taiga landscapes. There is also a low proportion of orographic low-flows channels in permafrost conditions. Orographic flood channels are not typical of landscapes of Eastern European groups and are found in Siberian landscape groups, which is explained by the combined influence of limiting conditions and types of permafrost. There is an increase in limited alluvial channels from Arctic tundra landscapes to landscapes to those of taiga groups. As a result of the assessment, it is shown that the shape of riverbeds is influenced by permafrost, determining the nature of riverbed formation in the region.

The paper presents the results of a comprehensive analysis of the situation with dangerous hydrological processes at the mouth reaches of the Pechora River (from the mouth of the Sula River to the Pechora Bay). The study used data from observations of water levels, discharges and ice phenomena at hydrological gauges (until 2022), information about inundations and adverse shallowing that occurred here, satellite images (since 1991). It was found that the main damage in the mouth of the Pechora River is caused by river inundations, one of the main factors of which is ice dams. It has also been established that the long-term repeatability of the icedam formation is actually greater than the gauge observation shows. During the spring flood, the floodplain is flooded almost annually, and in 25–50 and 10–14 % of years the water level exceeded the adverse and dangerous values. The city of Naryan-Mar often suffers from floods. Until the 1970s, these occurred almost every other year; more recently, there were major inundations in 1998, 2008, 2014 and 2017. The most dangerous season for the formation of ice dams and the occurrence of inundations has been determined. On a long-term scale, the frequency of flooding and ice-dam formation has remained practically unchanged, the duration of floodplain flooding has increased everywhere, whereas the time of the water level exceeding the adverse mark has increased in the river mouth segment upstream from the delta and decreased in the delta. The empirical dependencies between the water levels and the area of flooding, between maximum water levels and the duration of flooding are substantiated. There are four main scenarios of the channel of the Pechora River and delta branches opening from the ice cover in spring. The location of the main points of ice-dam formation has been specified. The third unfavorable hydrological process within the Pechora River mouth is adverse water runoff shallowing, which disrupts river navigation. In the vast majority of cases, it is associated not with low water levels in the delta, but with those in the middle and lower reaches of the Pechora River. This period lasts from August 11 to September 6. On a long-term scale, the situation with minimum levels in the summer and autumn season has improved. As regards other unfavorable hydrological phenomena — anomalous (by date) ice formation, sea-water intrusion into the delta branches, storm surges and wind-induced down-surges — it has been found that they do not cause damage either because of their low intensity and repeatability, or because they belong to other parts of the Pechora mouth region.

An overwhelming part of fresh waters is concentrated in environmentally sensitive small rivers, lakes and swamps. A complete lack of control over their state coupled with the poor economic development of the Arctic zone threatens to lead to large-scale regional and interregional disasters. The article presents an approach to the organisation of a system of control over the ecological state of fresh waters, based on the regularities and generalizations obtained by research and design organisations based on many years of research. It is proposed to locate observation points at reference water bodies selected on the basis of landscape-hydrological zoning of the controlled territory. The set of signal indicators determined at these points will consist of a small number of integral hydro-chemical parameters of water quality which allow describing the formation and development of negative ecological intra-water body processes, as well as, in general terms, the socio-economic consequences of these processes. In general, the proposed approach is the basis for the organisation of a signal system of freshwater monitoring aimed at informing the environmental authorities in advance about the need to take preventive measures to avoid a large-scale environmental crisis.

The paper presents research findings of the climatic factors responsible for the activation of thermal denudation processes leading to the formation of thermocirques in the central part of the Yamal Peninsula in the north of West Siberia. Based on a comparison of multi-temporal remote sensing (2010, 2013 and 2018) coupled with climate data, an analysis of the thermocirques activity in 2010–2018 was carried out. Thermocirques are specific topographic forms that arise because of the activation of cryogenic earth flows, the formation of which is caused by an increased seasonal thawing of the upper part of the ground ice on the slopes as compared to the previous years. Analysis of the monitoring data showed that in 2012 and 2013 all the types of surfaces are characterized by a significant increase in seasonal thawing compared to the previous period 1993–2011 (12 % increase on slopes), due to the summer air temperature, the amount of summer precipitation and the increased duration of the warm period. The results of the thermocirques activity analysis are shown on a map. The results of this local study were compared with those of a regional (Yamal and Gydan Peninsulas) remote sensing study of thermocirques. This showed a higher accuracy of the local study based on field monitoring and very-high-resolution satellite imagery. The analysis of the thermocirques activity showed that 1) over the period from 2010 to 2018 thermal denudation activity in the study area increased due to the anomalous climatic conditions in the spring-summer season of 2012, and then gradually decreased; 2) in addition to “classical” thermocirques, which were at different stages of activity in the time periods analyzed (2010, 2013 and 2018), a significant number of embryonic thermocirques were identified. Such thermocirques, just as the majority of small “classical” thermocirques, can only be identified on very-high-resolution satellite imagery.

The aim of the study was to develop quantitative criteria of iceberg hazard for the seas of the Russian Arctic based on the results of statistical processing of the data of regular satellite surveys. The study used non-commercial data of the visible spectral range from the Landsat-8 satellite (spatial resolution of 15 m) for 2014–2023. It is proposed that the criteria of iceberg danger be expressed in points. The main criterion is the value of the average daily density of icebergs in squares of a regular grid obtained for a particular month (season) of the year and expressed on a 5-point scale. Additional criteria included registration in the iceberg grid with a length of more than 200 m (extensive icebergs according to the classification of the World Meteorological Organization, WMO), icebergs with a surface height of more than 25 m, grounded icebergs (iceberg traps), and icebergs with high drift speeds (>1 km/hour). The additional criteria are estimated at 1 point on the iceberg hazard scale. To detect icebergs in the images, a technique was used based on statistical criteria for searching for gradient zones in the analysis of two-dimensional fields of satellite images. A convolutional neural network based on the U–Net architecture was used to automate the detection of grounded icebergs among drifting ice floes. Examples are given of the application of the criteria developed to the Severnaya Zemlya region. The possibility is discussed of zoning the water area according to the degree of iceberg hazard using the criteria suggested.

The paper deals with studies of ice elasticity and viscosity conducted in Russia and the USSR from the late XIX^th century till 1940. Research of these important characteristics requires special-purpose instruments of sufficient precision to measure small deformations. It was a serious challenge impeding further investigations. B.P. Veinberg was the first in Russia to examine these properties in 1905–1906 using an instrument specially designed and manufactured for this purpose. In the course of his studies, he obtained data on the ice internal friction coefficient and shear modulus. This research was of purely academic nature and was not meant to include practical issues. Around the same time the elastic and viscous properties of the ice cover started to be examined by researchers involved in the construction and maintenance of railway river crossings. Their efforts focused on ice deflections under load, which they studied using standard devices applied in railway transport and bridge construction. The need to determine the elastic limit emerged only in the 1920s in connection with the first mathematical models of railway crossings developed by B.N. Sergeyev and S.A. Bernstein. They attempted to infer the elasticity modulus from ice deflections measured at railway crossings. In the Soviet period, studies of the elastic and viscous properties of ice were almost abandoned. The most interesting investigations were carried out by V.N. Pinegin in 1922–1925. In the late 1930s, V.K. Maklashin conducted experiments to determine the ice compressibility coefficient. However, his work contained a lot of major inaccuracies, which raised some doubts as to the results he obtained. Little research done in Russia on ice elasticity and viscosity can be attributed to the lack of practical interest in the data regarding these ice properties.