Okeanologiâ

The average temperatures of the Northern Hemisphere for surface air, the lower troposphere and the upper layer of the ocean from 0 to 100 meters are considered. It turned out that all these time-series are similar to each other in that they consist of two components: a warming trend and fluctuations on an approximately ten-year scale superimposed on this trend. It is hypothesized that this quasi-decadal temperature variability is associated with the El Niño–Southern Oscillation. After removing trends from the series under study, their autocorrelation functions demonstrate an exponential decrease and subsequent fluctuations near zero with shifts of approximately 5 years or more, which theoretically makes it possible to predict their changes with a lead-time of 1–4 years. An analysis of the results of the “Historical” experiment of 58 CMIP6 models confirmed the conclusions drawn and showed that the quasi-decadal variability of the average surface air temperature of the Northern Hemisphere is significantly influenced by large volcanic eruptions. Results from the “piControl” experiment of 50 CMIP6 models demonstrated the ability to predict changes in average Northern Hemisphere temperatures several years into the future based on natural interannual climate variability, the main component of which is the El Niño–Southern Oscillation.

The study calculates the hue angles of the Black Sea and Sea of Azov water based on satellite and in situ measurements of the reflectance coefficient for 20192023. The correlation coefficient for the satellite and in situ hue angles is 0.92. Division of the reflectance spectra into subgroups according to the values of the hue angle is proposed for the study area. Satellite-derived values of absorption by dissolved organic matter(including detritus absorption) and backscattering by suspended particles have been compared in three ways: by empirical formulas for the hue angle, by a semianalytical algorithm for the spectral reflectance coefficient,and by the standard satellite algorithm (GIOP model). The empirical relationship is better at retrieving the absorption by dissolved organic matter than the standard satellite or semianalytical algorithms whereas for backscattering by suspended particles all three methods show similar quality of retrieving.

Methods of estimation the isotopic parameters (δD, δ¹⁸O) of the freshwater component in the river-sea transition zone are considered in this work. This research is based on samples collected at the end of the summer season along two meridional sections laying from the estuaries of the Ob and Yenisei rivers to the center of the Kara Sea. The runoff of these rivers has contrasting isotopic parameters contrasting (δ¹⁸O = –15.0 ± 0.3‰, δD = –112.7 ± 2.1‰ for the Ob and δ¹⁸O = –18.9 ± 0.6‰, δD = –142.2 ± 4.3‰ for the Yenisei). It has been established that river waters located within the surface layer of sea water do not have time to homogenize: in the center of the Ob-Yenisei plume, the part of Ob waters is 60%. Within river estuaries, FC is homogeneous only in the upper layer of water (less than 5 m); with depth, variations in δ¹⁸O(FC) values reach 16‰ for the Ob Bay and 12‰ for the Yenisei Bay, exceeding the annual course of seasonal variations of this value in river water. In the bottom layer for the estuarine zones of both rivers, the presence of a total FC with light isotopic characteristics corresponding to regional atmospheric precipitation is observed, that FC is supplied to the estuary zone with the waters of the Kara Sea.

The study of the contribution of bacteria (BAC), heterotrophic nanoflagellates (HNF) and viruses (VIR) to vertical matter fluxes on the shelves of the East Siberian Sea (ESS) and the Laptev Sea (LS) was carried out using sediment traps placed on buoy stations at depths of 18–55 m for 4–19 days. The value of the total organic carbon flux (TOC) contained in the cells of bacteria (BAC), heterotrophic nanoflagellates (HNF) and virus particles (VIR) in the ESS varied from 0.5 to 2.4 mg C m^–2 day^–1 and amounted to 1.1–4.9% of the total TOC flux, in the LS – from 0.7 to 5.2 mg C m^–2 day^–1 and amounted to 1.1–6.2% of the total TOC flux. The maximum values of flows were measured near the Lena River delta, the mouths of the Khatanga and Indigirka Rivers. The contribution of BAC, GNF and VIR to the total biomass of the microbial community attached to sinking particles was, on average, 59 ± 11%, and 28 ± 8%, 13 ± 9% for VSM and ML, respectively.

In 2020, the bottom communities of Rusanov Bay were studied for the first time and repeated benthic surveys were conducted in Blagopoluchiya and Tsivolki Bays (Novaya Zemlya archipelago, Kara Sea). Mass extinction of adult populations of the bivalve Portlandia arctica, which was dominant in 2013–2016, was noted in the inner parts of the bays. In all tree bays, the main share of the benthos in 2020 consisted of bivalves Mendicula ferruginosa and juveniles of Ennucula tenuis, Portlandia arctica, Yoldiella spp. In Rusanov Bay, the number of small and juvenile bivalves was the highest and reached 2900 ind/m² (92% of the total density). The high proportion of juveniles indicates instability of benthos and should lead to rapid transformation of inner bay communities over the next years. Environmental variability (terrestrial runoff, sedimentation, temperature characteristics of the bottom layer) and the invasion of the snow crab Chionoecetes opilio can be proposed as the reasons for the benthic community changes.

Belugas are gregarious and form different types of social groups, which may include both related and unrelated individuals. Apart from mother–calf dyads, there is almost no information about individual associations in beluga groups. Using photo-identification data, we investigated the social organization of belugas summering off the Solovetsky Islands in the White Sea, Russia, based on sightings of 122 individuals in a reproductive gathering off Cape Beluzhy, Solovetsky Island, in July – August 2022. Data analysis was carried out using the program SOCPROG 2.9. We have not found any social clusters with stable individual composition within the gathering. Nevertheless, some pairs of individuals, which usually included a female, had high association indices. In general, association indices in pairs decreased during the study period. These results could be influenced not only by the nature of social relationships among belugas, but also by the individual variance of visiting patterns to the area of the gathering. These factors cannot be differentiated within the framework of the current study. Associations of individuals outside the study area, as well as beyond the study period, remain unknown.

The bottom sediments of the upper part of the contourite drift located in a narrow linear depression belonging to the central part of the Kara Sea shelf were studied for the first time. According to the grain size distribution of the sediments, the drift belongs to the muddy contourites. Three main horizons of sedimentation were identified in three sediment cores up to 7 m long. The previously dated magnetic susceptibility peak at the base of the sediment cores indicates that the formation of the drift began in the postglacial period, more than 10 kyr ago. Local sedimentation conditions during the Holocene were influenced by repeated increases in river discharge, as indicated by the presence of desalination-tolerant species in the benthic foraminiferal assemblages. The increase in thickness of sediment core layers and drift deposits in general from south to north indirectly indicates the presence of a general submeridional trend in the Holocene and earlier bottom current.

Experimental deployment of surface meteorological moored buoy “Sea-Air-Wave Station” (SAWS) was performed during the expedition “European Arctic – 2024: a geologic annals of environmental and climate change” (96^th cruise of RV “Akademik Mstislav Keldysh”) in the north-eastern part of the Barents Sea. Mooring design and instrumentation demonstrated validity of the meteorological buoy for usage as part of National green-house monitoring system.

During the 67th cruise of the RV “Akademik Ioffe”, original materials were obtained characterizing the composition and structure of the epi- and mesopelagic fish communities, as well as their relative abundance and spatio-temporal variability in the subtropical central-eastern Atlantic. The results of the research will allow for comparison of deep-sea pelagic ichthyofauna in various regions of the tropical and central Atlantic.

During the cruise of RV “Akademik Oparin” an assessment of radioecological state of the Pacific Ocean east of Japan and Kuril Islands as well as Okhotsk and Japan seas was conducted in connection with polluted water discharge from Fukushima-1 NPP. Results of the first samples of surface analysis showed tritium content as 0.36–0.78 tritium units (0.04–0.09 Bk/l). The highest concentrations were found in the Kuroshio Extension stream and in the area of Southern Kuril Islands. Meanwhile it is ten thousands time lower than radio security norm. In the cruise samples of water, bottom sediments and marine biota were prepared to analyze radioisotopes of cesium, strontium, led, radium and others. Large volume of hydrographic, chemical, biological, gas-geochemical, mercury measurements and samplings was implemented. Mooring systems were recovered and deployed again. New data on water state and dynamics of the study region, as well as biogeochemical parameters and their interannual variability in association with climate change and increasing anthropogenic load were received.