Vol 64, No 3 (2024)

This article is a continuation and generalization of the work “On the similarity of quasi-geostrophic vortices against the background of large-scale barotropic currents” [6] (Oceanology, Zhmur, 2024, in print). In continuation of the above work, a similar formulation is considered, but for other types of background currents. In the quasi-geostrophic description for small Rossby numbers, the problem of the evolution of an arbitrary–shaped liquid volume with homogeneous potential vorticity of all vortex core particles in an equidistant background flow – horizontal flow with vertical shear and equidistant flow with barotrotropic and baroclinic components is presented. Ultimately, the problem boils down to an integro-differential equation for the evolution of the vortex core boundary. The study of this equation in dimensionless form allows us to find a set of dimensionless parameters that determine the similarity condition of the vortices under study.

The estimates of isotope parameters and sources of fresh water components for subsurface, intermediate, and deep waters of Western part of the Bering Sea were carried out using the isotope (δ¹⁸О, δD) data for 177 seawater samples. We show that subsurface, dichothermal and, partially, intermediate waters (< 1000 м) are freshened by the regional atmospheric precipitations. For these waters the next equations of relations between delta values and salinity were obtained:

δ¹⁸О = [0.39 ± 0.02]S – 13.52 ± 0.61 and δD = [3.1 ± 0.1]S – 107.0 ± 2.7.

A deeper (1000–2500 m) waters also freshened by atmospheric precipitations, but from the more south region (≈ 40–45 S). The deepest waters (2800–4300 m) are preserving their isotope signal obtained by freshening with meltwaters of Antarctic glacier ice. The distribution of isotope parameters with the depth shows that the vertical mixing at the ≈1000–2500 m depth take place. This process should influent on the re-distribution of the biogenic elements, dissolved oxygen, organic matter, and other components in waters of the Western part of the Bering Sea. Isotope composition of waters passing into the Arctic Ocean halocline (S = 33.1) from the Bering Sea are δ¹⁸О = –0.61‰, and δD = –5.4‰.

The results of hydrochemical studies of water bodies with varying degrees of development of anaerobic conditions (up to the appearance of meromixia with sulfide anoxia) located in the Porya Bay (Kandalaksha Bay of the White Sea, Kandalaksha State Nature Reserve) are presented. It is shown that these reservoirs, which are at different stages of isolation from the sea, have a unique hydrological and hydrochemical structure, which is formed at a certain stage of their evolution. The vertical stratification of waters, with the development of all phenomena accompanying stagnation, is more pronounced in the most distant parts of their water area from the sea, where an increased content of hydrogen sulfide (up to 16.5 mg/l), phosphates, silicon, nitrite and ammonium nitrogen is noted in the near-bottom anaerobic waters. However, the concentrations of all major ions are comparable to those in sea waters and practically do not change vertically. An analysis of the distribution of hydrochemical parameters of the distant reach of the Ozerki lagoon made it possible to conclude that, as a result of changes that have occurred with this reservoir over the past 90 years, it can now most likely be classified as meromictic.

Based on contact data, the dynamics of the abundance (N) and biomass (B) of phytoplankton in 2013–2014 and the concentration of chlorophyll a (C_сhl) in 2000–2003 and 2008–2021 were analyzed using fast Fourier transform (FFT) under conditions of changing water temperature (T) in the vicinity of Sevastopol in the Black Sea. Estimates of the contribution made by the variability of the annual and semiannual harmonics of N, B, C_chl, T to the seasonal cycle amounted to more than 56% for all parameters. A significant relationship between B and C_chl (r < –0.83) at two stations indicates the aging of microalgae. The dominance of different groups of microalgae in the phytoplankton biomass has been detected. A typical period of 2–4 years is distinguished in the interannual variability of C_chl and T in different seasons.

During the 89th cruise of the R/V Akademik Mstislav Keldysh in September-October 2022, a study of the bottom communities of the Kara Sea was carried out using the bottom trawl Sigsby and the ROV Videomodul, as well as plankton sampling usin Bongo net in order to register crab larvae in the water column. In the eastern part of the Kara Sea, in the section from the Voronin Trough towards the coast of Taimyr, starting from a depth of 490 m, single large individuals of the snow crab were found for the first time. At the same time, not a single crab larvae was caught, which indicates the penetration of the adult stages of the snow crab into these areas along the bottom. On the contrary, in the western part of the sea and in the Bay of Prosperity, high numbers of all size groups of snow crab at the bottom, as well as crab larvae in the water column were observed. Differences in the speed and nature of the introduction of the snow crab are explained by the contrast of the ice conditions in the western and eastern regions of the Kara Sea. Possibly, further development of the snow crab population in the east of the Kara Sea should be expected in connection with the tendencies for an increase in the duration of the ice-free period in the Arctic.

The ice-gouging topography of the southwestern part of the Kara Sea bed is a result of the impact of icebergs and sea ice. During 52 cruise of the R/V Akademik Nikolaj Strakhov using a multibeam echo sounder we collected a representative data of key parameters of ice scours (location, orientation, depth, width) for the first time, which allows us to draw conclusions on a regional scale. We revealed regularities in the distribution of the ice scours both in space and in depth and their density in different parts of the seabed. It was revealed that the maximum dimensions of the ice scours decrease with the distance from the sources of iceberg calving from NW to SE. The orientation of the ice scours correlates with the main drift directions of the icebergs. Most of the ice scours are located at depths up to 220 m and could have formed both at modern and at lower sea level (in post-glacial time). We identified a high degree of the seabed transformation by ice-gouging processes in the southwestern part of the Kara Sea.

A comprehensive analysis of geological and geophysical data characterizing the structure of the eastern continental margin of India and the adjacent part of the bottom of the Bay of Bengal has been carried out. According to the structural and tectonic features, three sectors are distinguished: southern, central and northern, the natural boundaries between which are the fault zones of the aulacogens Makhanadi and Godavari-Krishna. In the central sector, the pericontinental East Indian Plateau adjoins the continental slope. In 2003, R/V Mezen acquired data using deep seismic sounding method on two profiles in this region. The obtained data and their geological interpretation made it possible to identify the “reduced” continental crust. It is characterized by reduced thickness of the upper, middle and lower layers. A conclusion is made about the continental nature of the East Indian Plateau and the northern part of the Ridge 85° adjacent to it. The light sialic and effusive rocks that form the top of the ridge give a negative gravimetric anomaly in Fay's reduction, which is its outstanding feature.

92^d cruise of R/V “Akademik Mstislav Keldysh” was organized by Shirshov Institute of Oceanology in a frame of long-term Program “Marine Ecosystems of Siberian Arctic” and was held from 5 October to 7 November 2023. 76 scientists from the institutes of Russian Academy of Sciences, National Research Center Kurchatov Institute, Moscow State University, Moscow Institute of Physics and Technology, VNIRO and MES of Russia participated in the cruise. Coordinated hydrophysical, hydrochemical, biooceanological, geochemical research were carried out in the eastern part of the Kara Sea in the period of seasonal ice formation, as well as in the Ob river estuary and fjords of Novaya Zemlya archipelago. Conditions of largest disposals of radioactive waste in the Kara Sea were evaluated.