Okeanologiâ

Based on the data of CTD-profiles, acquired in 2010–2023 in the northeastern part of the Black Sea, at the SIO RAS Gelendzhik study site, relative heat content of active layer was estimated, along with its changes during the warm period, from April to October. The heat content was also calculated individually for upper mixed layer and seasonal thermocline, which constitute the active layer. These real data estimations were compared with heat content calculations based on reanalysis datasets ERA5, NCEP CFSv2 and WHOI OAFlux. It was shown that NCEP CFSv2 provides the result closest to the real data.

For the period of satellite altimetry observations 1993–2018, the zonal distribution of the linear meridional shift of the jet structure and the change in the intensity of currents in the sector of the Antarctic Circumpolar Current (ACC) south of Africa (9.875°W–25.125°E) were estimated. The jet structure is understood as the alternation in the meridional direction of zones of increased and decreased values of the modulus of the absolute dynamic topography (ADT) gradient, |∇ζ|. The work was carried out using the methodology developed earlier and supplemented in this article, based on the calculations of linear regressions, which also includes an assessment of calculation errors. To estimate the zonal distributions, the sector was divided into meridional bands, for each of which a calculation was carried out. The optimum width of the band is estimated at 2.5° lon. The presence of a noticeable zonal inhomogeneity in the shift of the jet structure and changes in the intensity of the currents are shown. This inhomogeneity is obviously associated with quantitative discrepancies in the calculations of these parameters with division into bands, with their subsequent averaging over the zonal series, and without division into bands. Qualitatively, the patterns of shifts in the jet structure and changes in the intensity of flows with and without separation into bands are similar.

Based on the results of long-term research in the Eurasian sector of the Arctic Ocean, a statistical summary of the chemical composition of atmospheric aerosol is presented: the concentrations of 8 ions, 22 microelements, organic and elemental carbon (OC, EC), as well as the isotopic composition of carbon δ¹³C. The average aerosol characteristics had been: 5.14 μg/m³ for the total ion concentration with a predominant contribution (72%) of Na⁺ and Cl^– ions; 175 ng/m³ for the total concentration of trace elements. with the main contribution (70%) of terrigenous elements Fe and Al; 700 ng/m³ for the OC concentration; 32 ng/m³ for the ЕC concentration; –27.9‰ for the isotopic composition δ¹³C. High enrichment factors for the elements Cr, Ni, Se, Mo, Sn, Pb, Cu, Zn, As, Ag and Sb (relative to the composition of the earth's crust) were revealed, which indicates their technogenic origin. The spatial distribution of concentrations of all ions is characterized by a decrease (on average, 3.5 times) from the Norwegian Sea to the Chukchi Sea. The spatial distribution of trace element concentrations was divided into 3 groups with maxima over the Norwegian or Barents or Kara Seas and a minimum over the Chukchi Sea. The characteristics of carbon-containing aerosol also show a trend of change in an easterly direction: a decrease in OC and EC concentrations and a heavier isotopic composition of carbon.

Based on the data obtained during 7 expeditions (2017–2023) to the Kara Sea, seasonal variation in the contribution of phytoplankton size groups to the total values of primary production (PP) and chlorophyll a (Chl) are examined for the first time. Micro- and nanophytoplankton (MPh+NPh) (> 3 µm) dominated in the community composition during the entire ice-free period (June–October). Its predominance was especially noticeable during the spring “bloom” immediately after first-year sea-ice retreat (up to 97% for PP and up to 93% for Chl). The role of picophytoplankton (PPh) (< 3 µm) increased in summer (July, August) (up to 50% for PP and up to 44% for Chl) and decreased by the end of the growing season (September, October). Seasonal variation in the size composition of phytoplankton during the growing season was determined mainly by variability in water temperature and incoming solar radiation. The contribution of PPh to total Chl increased (up to 51%) at the depths of the deep chlorophyll maximum in July and August. The assimilation activity of PPh was higher than that of MPh+NPh in July–September, with an increase in its contribution to the total PP and Chl. For the first time, annual PP of the phytoplankton size groups in the Kara Sea was assessed, 8 ТgС (65%) for MPh+NPh and 5 ТgС (35%) for PPh.

The results of the first combined instrumental and visual aerial survey of cetaceans in the northeastern part of the Black Sea, conducted in July 2019, are presented. The research area, covering 11,244 km², extended from Sochi to Anapa, encompassing the 12-mile zone of the Black Sea (territorial sea of the Russian Federation). The total estimated number of cetaceans is 17.505 ± 2,678 individuals (CL90% 13.484–22,206). Common dolphins comprised approximately 69% of this number, bottlenose dolphins accounted for 22%, and harbor porpoise for 9%. The maximum density of common dolphins reached 8.13 individuals/km², bottlenose dolphins at 1.87 individuals/km², and harbor porpoise at 0.62 individuals/km². High-density of all three species was found in the northern part of the surveyed area, while low-density was observed in its middle part. The data obtained in this survey are compared with the results of other counts of Black Sea cetaceans, and a comparative assessment of instrumental and visual methods is provided.

Based on sedimentological, isotope-geochemical and micropaleontological parameters of bottom sediments of the core AMK-5188, differences in the natural environment of the last interglacial of the Late Pleistocene (marine oxygen isotope substage 5e) and the Holocene in the Lofoten Basin of the Norwegian Sea were revealed. The local thermal optimum of the last interglacial was shifted to the second half of substage 5e ~124–115 thousand years ago and consisted of two short intervals separated by strong cooling ~122–120 thousand years ago. In the Early-Middle Holocene ~10–3 thousand years ago, a long stable climate optimum was noted for main identified parameters, and a short paleotemperature minimum occurred in the Late Holocene ~3–2 thousand years ago during the regional Neoglacial cooling.

In 1965, the K-27 submarine with an emergency portside reactor with unloaded spent nuclear fuel (SNF) was flooded in Stepovoye Bay (Novaya Zemlya). The source of radioactivity is nuclear fuel in the port side reactor and fuel carried into the corresponding steam generator. Before flooding, the elements of the power plant were sealed with furfural, and the entire compartment was then filled with bitumen. It is believed that when water entering the reactor core, a self-sustaining fission chain reaction (SCR) may occur. However, this process is possible only if the above-mentioned protective barriers are violated. The state of the protective barriers can be judged by the magnitude and variations of the radioactive background on the deck and near the submarine on the ground. Thus, the most important task of monitoring and preventing an emergency situation on the K-27 submarine is the constant monitoring of the environment (ecology) in Stepovoy Bay in general and near the submerged submarine in particular. The article considers the results of research on the submarine and its environment, including the R/V Akademik Mstislav Keldysh (cruise 92, 2023) expedition, when the parameters of the radioactive background were for the first time measured directly on the submarine robust hull in the area of the reactor compartment.

Oceanographic research has been carried out to study the flow of Antarctic Bottom Water along the Vidal abyssal channel and the Vema Fracture Zone in the tropical part of the northwestern Atlantic. Research was also carried out in the North Equatorial Countercurrent and on a section through the Amazon River plume in the open ocean.

During the 70th cruise of the RV Academic Oparin geophysical, hydrological and atmospheric studies within the shelf Chukchi Sea were conducted. New data on the structure sea bottom, sedimentary cover, features of the magnetic field, spatial distribution of greenhouse gases at the water-atmosphere boundary.