The study of the dynamics of the near-surface layer of water when sinking from the surface of a finite volume of water with negative buoyancy (or the thermal) is performed by using qualitative experiments in the hydrodynamic flume and numerical simulation of the phenomenon under study. Laboratory experiments have demonstrated vortex and highly unsteady nature of the flow of the density-inhomogeneous water generated by immersion from the surface of the final volume of water with negative buoyancy. All usually observed stages of transformation of the shape of water thermal were recorded in laboratory – the “mushroom”, the vortex ring and its decay. Numerical simulation confirmed vortex and shortlived nature of the emerging flow and allowed for detalisation the processes of immersion of the finite volume of salt water in a fresh environment. The use of three additional model fields of neutrally buoyant tracers made it possible to track the variability of the shape of the thermal, as well as the processes of mixing and involvement of fresh water into the motion. Detalisation of vertical circulation in the vicinity of the sinking thermal showed the presence of upward movements of fresh water on its periphery. In natural conditions, this circumstance should prevent for some time the possibility of generation of the next thermal at the given location of the sea surface.

Analysis of the monthly average data of the temperature of the Baltic Sea on the surface and various depths showed its significant growth over the past decades. At the same time, the observed temperature increase is not evenly distributed throughout the Baltic Sea, as the temperature increased most strongly in the Gulf of Finland and Riga. Against this growth, temperature oscillations with periods ranging from 2 to 6 years, ~8 years and ~14 years were found. The relationships between these oscillations and the El Niño, the North Atlantic Oscillation and the North Atlantic Current, respectively, are shown. It was found that the influence of El Niño captures the top 10 meters of the Baltic Sea, the connection with the North Atlantic Oscillation is traced to a depth of 52 meters, and the influence of the North Atlantic Current is maintained to a depth of 78 meters. It has been shown that these fluctuations exerted the strongest influence on the temperature of the Baltic Sea from the mid-1970s to the end of the 1990s. The influence of global climate shifts 1976/77 and 1998/99 on interdecadal changes in the temperature of the Baltic Sea has been detected. It has been suggested that the Global Atmospheric Oscillation acts as a synchronizing link between the El Niño, the North Atlantic Oscillation and the interannual variability of the temperature of the Baltic Sea.

Translated by E.S. Kochetkova

Temperature and salinity variability in the upper 20-meter ocean layer in the 1950–2014 time interval were analyzed on the basis of the observational data. Four typical regions were selected for this study in the central part of the Arctic basin and two regions on its border with the Laptev Sea. The analysis allowed revealing that until the 1990s, when most of the Arctic basin was covered with perennial ice all year round, the temporal variability of the thermohaline parameters in the upper mixed layer in all the considered areas was small throughout the year. Since mid-1990s, multidirectional changes in the thermohaline parameters in the upper layer have been observed in the western and eastern parts of the Arctic basin. In the Western region in the winter season, salinization and cooling of surface waters are happening, whereas in the eastern Arctic, on the contrary, there is strong desalination and a corresponding increase of water temperature. One of the main reasons for the desalination of surface waters in the eastern Arctic is a reduction in the area of perennial ice and its replacement by seasonal one against the background of increased riverine water discharge and change in the atmospheric circulation over the Arctic. The salinization of surface waters in the western Arctic is associated with an increase in the supply of saline Atlantic waters from the Fram Strait and their rise to the surface under conditions of increased seasonality of Arctic sea ice, which refers to an increase in the duration of the melting season.

Translated by E.S. Kochetkova

The paper presents generalized results of a study on submesoscale eddies’ surface manifestations in the Barents, Kara, and White Seas based on the analysis of about 3.5 thousand satellite radar images during ice-free periods for several years from 2007 to 2012. For general features determination of submesoscale eddies’ activity against processes of larger scale, sea surface temperature data, which allowed assessment of frontal zones position, and tidal data were used the same period. About 4.5 thousand structures were registered in the investigated seas. It is shown that submesoscale eddies are a common phenomenon in the warm season in the areas of the Barents, Kara, and the White Seas. Eddy structures with a diameter from 2 to 4 km are most often registered. It has been established that the cyclonic type of eddies’ manifestations is a prevalent type of structures, while the size of anticyclonic structures is larger on average. The maximum number of eddies is observed in the initial period of formation of the seasonal near-surface pycnocline. Comparison of the positions of eddies’ surface manifestations, the frontal zone positions, and the bottom topography showed that the frequent occurrence of eddies is predominantly observed near and within the areas of the variability of the frontal zones. And also eddy structures are registered in regions where there are significant bottom irregularities. The maximum number of eddy structures in these regions was recorded principally during the period of a spring tide.

Translated by E.S. Kochetkova

We studied mesoscale eddies in the Lofoten Basin of the Norwegian Sea. The automatic eddy identification and tracking algorithm were applied to satellite altimetry. Images of 166,000 cyclonic and 169,395 anticyclonic eddies were detected in the Lofoten Basin from 1993 to 2017, then the tracking procedure was applied to them. We analyzed tracks of long-lived (lifetime more than 35 days) individual eddies. They are 120 cyclonic and 210 anticyclonic eddies. We studied a spatial distribution of mesoscale eddies in the Lofoten Basin as well as locations of their generation and dissipation. A statistical analysis of their characteristics also was carried out. We show that two predominant systems of mesoscale eddy formation exist in the Lofoten Basin. This fact may reflect two different mechanisms of eddy generation. The first one is the separation of eddies from the Norwegian current during its meandering. The second one is the direct generation of eddies inside the Lofoten Basin. There are three distinct areas of eddy generation in the frontal zone of the Norwegian current, from where eddies move to the west and north-west, forming three main trajectories. Anticyclonic eddies dominate in the area of the Lofoten vortex. Having arisen, they rotate intensively within the area of the Lofoten vortex in the anticyclonic gyre and interact obviously with the Lofoten vortex by merging. However, cyclonic eddies structures in the area of the Lofoten vortex are also found in a sufficient amount, and they are localized in the vicinity of two points with centers of 69.5° N, 4° E, and 70° N, 2.5° E. These cyclonic eddies are located in an area with cyclonic vorticity surrounding the Lofoten vortex like an annulus (shielded vortex). Mesoscale eddies that enter the area of the Lofoten vortex from outside are formed mainly in the region of the Norwegian current and tend to have the cyclonic rotation. We demonstrate that anticyclonic mesoscale eddies in the Lofoten Basin are formed mostly in the frontal zone of the Norwegian current and decay not too far from the place of their formation, while cyclonic eddies can form in different places in the Lofoten Basin. The number of eddies is much smaller in the western part of the Lofoten Basin than in other parts of it.

This study is based on numerical experiments data analysis performed using the Delft3D model configuration adapted for Ob Bay region. The work discusses the results of numerical simulation of the intra-annual variability of individual parameters of the thermo-, hydrodynamic and ice regime of investigated area on a computational grid with a spatial resolution of 50–100 m horizontally and 1–2 m depthly, and using the non-hydrostatic mode. The selection of control parameters values made possible to bring this configuration of the model to a stable mode of function and most fully adapt it to the conditions of high (polar) latitudes.

The performed numerical experiments showed an adequate reproduction of the hydrophysical and ice regime of Ob Bay during the calculation period. The data obtained in calculations process were compared with the available in-situ observations made in Ob Bay. To demonstrate the operation quality of the model’s adaptable configuration, based on the results of modeling the current velocity, fluctuations in sea level and ice cover thickness, an estimate of the calculation errors was performed. A comparative analysis of the evolution of selected parameters obtained as a result of numerical experiments with observational data demonstrated the positive capabilities of the Delft3D model complex. The maximum values of the calculation errors mainly depend on the quality of the input data. Thus, the Delft3D model complex adapted to Ob Bay area can be used to successfully resolve some applied hydrometeorological, morphological, and environmental problems in the development and operation of this Arctic region.

There is considered methodology and results of computer processing of vector ice maps of the AARI archive for the period 1998–2018. As a result of the maps processing, there were obtained long-standing series of total lengths of the Sabetta Port – the Bering Strait route legs within fast ice, within close floating ice, within the ice with presence of certain age categories of the ice and some particular concentrations of old ice and thick first-year ice for ten-days periods (decades) during April and May. The series were checked for the presence of trends by the method of integral curves, and were tested for heterogeneity using Wilcoxon–Mann–Whitney and Siegel–Tukey rank non-parametric criteria. There have been analyzed more than four thousand values of the lengths. We obtained the following conclusions: the lengths of the route within fast ice and within close floating ice with presence of old ice decreased. The lengths of the route within close floating ice, ones within close floating ice with presence of medium first-year ice and thick first-year ice increased. As well as there were increased the lengths of the route within close floating ice with partial concentration of thick first-year ice and total concentration of thick and medium first-year ice in five or more tenths. The decrease of the route length within old ice is partially compensated by the route length increase within thick first-year ice. The decrease and increase have almost the same values.

Within the framework of the essay the main periods of the National Hydrographic Black Sea Service development are presented. Pre-revolutionary (1895–1917) period and Soviet pre-war one (1917–1940) of the hydrography development are shown. The role of the Black Sea Oceanographic Expedition (1923–1935) and the Azov-Black Sea scientific-commercial expedition (1922–1928) in the history of the Black Sea research is described. Relationship of the hydrography and the Black Sea hydrophysical station development is presented. The results of hydrographic research till 1940 are shown briefly. For the first time, the Black Sea Oceanographic Expedition gathered a detailed material on the conditions of the sea water existence, including the hydrophysical ones. One of the most important results of the Azov-Black Sea scientificcommercial expedition, which still retain scientific importance, was the position on the system of circular currents in the western and eastern parts of the Black Sea – so-called Knipovich glasses. The general conclusion is the fact that hydrographic studies made a significant contribution to the initial study of the hydrophysical fields of the Black Sea, the same studies have served as the basis for the development of oceanography and its new branches, such as marine physics.