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Vol 65, No 3 (2025)
Физика моря
HYDROLOGICAL AND HYDROCHEMICAL FEATURES OF THEOB ESTUARY (KARA SEA) IN THE SEASON PRECEDING WINTER
Abstract
According to the data obtained during cruise 92 of the RV Akademik Mstislav Keldysh on October 11–13, 2023, in the northern part of the Ob estuary, the submeridional position of the estuarine front is shown under conditions of small discharge of the Ob River. The paper discusses the influence of external factors (river runoff, wind stress, tides) on the hydrological and hydrochemical structure of waters in the Ob estuary. Based on the data obtained, 4 types of waters are identified that form a complex thermohaline structure in the northern part of the Ob estuary and the adjacent shallow shelf of the Kara Sea, separated by frontal sections with sharp vertical density gradients.
Okeanologiâ. 2025;65(3):363-375
363-375
Modern distribution and verification of detected natural oil seeps in the Azov-Black Sea basin
Abstract
The results of monitoring of natural oil seeps in the Azov-Black Sea basin with synthetic aperture radar (SAR) in the period from 2020 to 2022 are analyzed. The SAR images of European satellites Sentinel-1A and Sentinel-1B were used for their search, detection and study. Using the geoinformation approach the main areas of oil seepage were identified and new oil seeps were detected. Their verification was carried out by analyzing all available information on geological and geophysical features of the water basins experimentally by subsatellite observations and measurements as well as by alternative remote sensing methods such as high resolution optical imagery. This allowed identifying twenty-eight oil seep sources in the Black Sea and one in the Sea of Azov. It is shown the study of natural oil seeps, their distribution and current activity is one of the important research tasks that is currently receiving considerable attention.
Okeanologiâ. 2025;65(3):376-392
376-392
GAS-GEOCHEMICAL, HYDROLOGICAL, AND BIOOPTICAL CHARACTERISTICS OF THE SHALLOW NORTHEASTERN SHELF OF SAKHALIN ISLAND
Abstract
The paper discusses the theoretical and practical aspects of the relationship between bio-optical parameters (chlorophyll-a concentration, colored dissolved organic matter, turbidity) and the distribution of dissolved gases (methane, helium, hydrogen, hydrogen sulfide) in seawater. Comprehensive studies of the gas geochemical, hydrological, and bio-optical parameters of the shallow northeastern shelf of Sakhalin Island (Sea of Okhotsk) are based on data obtained during cruise No. 68 of the RV “Akademik Oparin” in August 2023. It has been shown that during the warm period of the year, the study area includes waters with various bio-optical characteristics, influenced by river runoff, hydrocarbon-rich shelf areas, active phytoplankton development, and water dynamics. Bio-optical measurements allow for distinguishing the main branch of the East-Sakhalin Current and its shelf branch, in which increased concentrations of dissolved gases are present, emanating from benthic sources on the eastern shelf of Sakhalin Island.
Okeanologiâ. 2025;65(3):393-407
393-407
Assimilation of Argo profile measurements and sea surface temperature data by the NEMO ocean circulation model using an ensemble Kalman filter and three-dimensional variational analysis
Abstract
The results of modelling the thermohaline fields of the World Ocean obtained with the NEMO model using assimilations data from ARGO profiling floats and ocean surface temperature (SST) with the two different oceanographic data assimilation systems (ODAS) are presented. One system uses three-dimensional variational scheme 3D‑Var, and the other ODAS employs the ensemble Kalman filter LETKF. It is shown that both ODAS reproduce three-dimensional fields of temperature and salinity approximately equally, but the ODAS based on the ensemble Kalman filter better reproduces SST in the open ocean.
Okeanologiâ. 2025;65(3):408-421
408-421
Химия моря
DISTRIBUTIONS AND FLUXES OF NUTRIENTS IN THE BAYSOF THE SHANTAR ARCHIPELAGO
Abstract
The results of measurements of nutrients (silicates, inorganic and organic forms of nitrogen and phosphorus) content obtained in the Shantar Archipelago (ShA) water area in July 2016 and September 2022 are presented. It was found that photosynthesis results in the preferential removal of inorganic forms of nitrogen and phosphorus from surface waters. River runoff leads to enrichment of the bays in the ShA area with silicon and dissolved organic carbon. It was demonstrated the important role of spawning salmon in the enrichment of Academy Bay by total phosphorus and total nitrogen as well. It was estimated that migration of the juvenile salmon from ShA area to the open part of the Sea of Okhotsk is significant transport of the total phosphorus and total nitrogen. Application of the LOICZ model to the ShA area showed that the main source of different forms of nitrogen and phosphorus is the near-bottom waters of the Sea of Okhotsk (about 80–90% from total nutrients runoff to the bays). The model is based on ideas about estuarine water circulation, which maintains stable long-term content of nutrients in the bays of the ShA, which are comparatively geographically isolated from the Sea of Okhotsk. An assumption was made that salt marshes along the coastline of the ShA could be an important source of nutrients, and production of organic matter. The main sink of nutrients is outflow upper layer of the bays into the open sea.
Okeanologiâ. 2025;65(3):422-437
422-437
Морская биология
Assessment of inorganic carbon input by mollusks to the coastal zone of the North-Eastern sector of the Black Sea in 2008–2023
Abstract
The masses of inorganic carbon entering the bottom sediments of the northeastern shelf and slope of the Black Sea as a result of the activity of benthic mollusks have been quantitatively assessed. The most effective depths of carbonate matter formation by mollusks are 10–15 m and 60–70 m. Below 80 m, the contribution of this source to the supply of biogenic carbonate to sediments decreases sharply. Spatial and temporal heterogeneity of biomass distribution and inorganic carbon input by mollusks within the same depth belt was revealed. The greatest fluctuations of the input values were observed in the most carbonate productive zone: depths from 10 to 30 m.
Okeanologiâ. 2025;65(3):474-487
474-487
Zooplankton of the Laptev Sea: is the “effect of the continental slope” manifested in the distribution, feeding activity and grazing impact on phytoplankton?
Abstract
Mesozooplankton composition, distribution, and grazing in the areas of the continental slope, outer shelf and deep basin of the Laptev Sea were studied. Data were obtained in August–September 2018 during the cruise # 72 of the RV Akademik Mstislav Keldysh at two quasi-meridional sections. Zooplankton biomass (DW) in the 0–bottom layer increased with depth from 3–5 g ∙ m–2 on the shelf to 9–17 g ∙ m–2 above the slope and 12–17 g ∙ m–2 in deep-water areas. Over the shelf and slope, the share of Calanus glacialis in the total biomass was 80% and 45%, and it decreased to 32% in the deep-water area while C. hyperboreus’ increased to 39%. Contrary to the present concept of an of increased plankton concentration “belt” over the continental slope, no increase in the total zooplankton biomass was found in this area. Difference in the timing of the seasonal ice retreat was significant for the development of the C. glacialis and had virtually no effect on the population dynamics of C. hyperboreus and Metridia longa. Daily rations through herbivory did not cover metabolic expenditures. Daily zooplankton grazing impact on phytoplankton of the size fraction > 3 μm was 0.4–2% of phytoplankton biomass on the shelf, 7–10% above the slope, and 1.5–6% in the deep-water area.
Okeanologiâ. 2025;65(3):438-459
438-459
Bioluminescence and plankton communities in the Atlantic sector of the Southern Ocean
Abstract
Vertical bathyphotometric casts of the bioluminescent potential by the Salpa MA+ probe was carried out from January through February 2022 at 37 stations in the photic layer in the Bransfield Strait, the Antarctic Strait and the northwestern part of the Weddell Sea during the 87th Antarctic Expedition of the research vessel “Academician Mstislav Keldysh”. Vertical casts were accompanied by measurements of temperature, electrical conductivity, photosynthetically active radiation and collection of plankton samples with their subsequent processing. 7 bioluminescent plankton species have been identified, namely: Pelagobia longicirrata Greeff, 1879, Protoperidinium depressum (J.W. Bailey) Balech, 1974, Protoperidinium antharcticum, Metridia gerlachei Giesbrecht, 1902, Oithona similis Claus, 1866, Euphausia superba Dana, 1850 and Salpa thompsoni Foxton, 1961. Comprehensive studies have shown that the spatial structure of the bioluminescent potential field (its vertical and horizontal components) is formed by two main factors: the taxonomic structure of the plankton community and the thermohaline structure of the biotope. The species and taxonomic groups dominating the formation of bioluminescent potential differed significantly in all three research areas. The characteristics of the thermohaline structure in them were significantly different as well.
Okeanologiâ. 2025;65(3):460-473
460-473
Морская геология
Origin of Gaussberg volcano within the continental margin of the Antarctic continent (petrogeochemical features and geodynamic model)
Abstract
On the coast of East Antarctica, in the area of 89 degrees east longitude, the Gaussberg volcano was discovered with rare lamproite lavas of Pleistocene age. To explain the origin of this rare volcanism, we calculated the distributions of temperature anomalies and mantle flow velocities for the South Polar Region. Numerical calculations show that the vertical flows of the hot material of the Kerguelen plume flatten closer to the Earth’s surface and then the hot material of this plume is transported by subhorizontal currents in the upper mantle to the southeast to the edge of the lithosphere of East Antarctica. This process can cause melting of the edge of the continental lithosphere. The molten material rises to the surface and erupts in our proposed volcanic province of Gaussberg. Based on a detailed analysis of the subglacial relief in this area, it can be assumed that there are other subglacial volcanoes.
Okeanologiâ. 2025;65(3):488-498
488-498
GEOLOGICAL STRUCTURE AND PROSPECTS OF OIL AND GASBEARING AT THE CONTINENTAL MARGIN OF TANZANIA
Abstract
On the continental margin of Tanzania two big sedimentary basins – Tanzanian and Rovuma are distinguishing. Within the Tanzanian basin the following six subbasins from north to south along the littoral are distinguishing: Tanga, Pemba-Zanzibar, Latam, Rufidji, Mafia and Mandava. The big part of Tanzania is situated on the East African plateau. Sedimentary cover of the basin is presented by Phanerozoic deposits of 7–10 km thickness on the Archean basement. The Rovuma basin consists by two blocks Mrvara and Linde. The basin is characterized as a passive continental margin with a complex tectonic history. Rovuma basin is the principal gas bearing basin in the country. The formation of gas accumulations on the southeastern continental margin of Africa is associated with the spread of the Karoo complex, dated to the Permian-Triassic age. Analysis of more than 25 discoveries gas fields on the Tanzanian continental margin results to conclusion that all discovered gas fields gravitate mainly to the western side of the blocks. Large gas accumulation is marked in the deepwater areas, on the slope. Moreover, large gas discoveries have been made in the south of Tanzania. As far as advancement forward to the north the quantity and reserves of gas fields reduced. At the north of Tanzania gas accumulations have not been found, but oil accumulations have been noted.
Okeanologiâ. 2025;65(3):512-523
512-523
MAGNETIC ANOMALIES OF THE SOUTHEASTERN PARTOF THE KING THROUGH, NORTHEASTERN ATLANTIC
Abstract
TThe results of geomagnetic studies of the southeastern part of the King Trough and the central segment of the Azores-Biscay Rise, carried out in the Northeast Atlantic in 2023 on the 55th cruise of the RV “Akademik Nikolai Strakhov” are presented. These are the first systematic measurements of the magnetic field, which made it possible to construct a map of the magnetic anomaly of the study area. Intense magnetic anomalies were identified on the ridges bounding the King Trough, as well as linear anomalies on its flanks and in the southeastern part of the study area in the central segment of the Azores-Biscay rise. Spectral analysis and transformations of the magnetic anomaly indicate the existence of deep anomalies within the polygon. The intense deep anomalies are of volcanic origin and were formed in a different geomagnetic epoch than the deep parts and flanks of the King Trough. The results confirm the hypothesis of a complex two- or multi-stage formation of geological structures at the King Trough, with the exception of its southeastern part, which belongs to the Azores-Biscay Rise.
Okeanologiâ. 2025;65(3):499-511
499-511
Информация
Approbaton of a climate monitoring system based on moored platforms, observatories and shipboard studies in the 96th cruise of the research vessel “Akademik Mstislav Keldysh”
Abstract
In the tenth multidisciplinary expedition under the geosystems research program of the Shirshov Institute of Oceanology of the Russian Academy of Sciences “European Arctic: Geological Record of Environmental and Climate Change” to the Barents and Kara seas in July–August 2024, new data on atlantification and methane emission were obtained on the Eurasian Western Arctic Shelf. The research is aimed at developing a National system for monitoring climate change and climate-active substances based on the use of moored autonomous platforms, observatories, and vessel based observations.
Okeanologiâ. 2025;65(3):524-527
524-527
SOURCES OF RADIOACTIVE POLLUTION IN THE ARCTIC IN 2024 (97TH CRUISE OF THE RV “AKADEMIK MSTISLAV KELDYSH”)
Abstract
The information reports on the organization, conduct and main results obtained during expedition 97th of the RV “Akademik Mstislav Keldysh” to the Kara Sea on 01.09–06.10.2024. The purpose of the expedition is to study the state of underwater radioactive waste burials and ecology in the bays of Novaya Zemlya and the Novaya Zemlya Depression. In addition to traditional oceanographic instruments, underwater towed and remote-operated vehicles equipped with video, sonar and gamma-ray spectrometry equipment were used to conduct research. The work was carried out on board the RV, and in shallow water from a ship's boat. Benthos and bottom sediment samples were taken, as well as hydrological measurements. For the first time, burials of a number of objects have been confirmed, as well as detailed information about known objects using stereo imaging was obtained.
Okeanologiâ. 2025;65(3):528-531
528-531
RESEARCH OF THE CURRENT STATE OF THE FISH COMMUNITY OF THE EASTERN BARENTS AND WESTERN KARA SEAS IN SUMMER 2024
Abstract
During marine expedition at RV “Dalniye Zelentsy” in the summer of 2024, an assessment of the current state of the fishing communities of the eastern part of the Barents and western parts of the Kara Seas was carried out. In the north-east of the Kara Sea, a unique ichthyological survey was carried out using a coordinate grid repeating the research of 1930–1935. Ichthyological trawling has also been carried out in the Barents and the Kara Sea along of the Novaya Zemlya archipelago. As a result of the research, new data have been obtained on the species composition, abundance, biomass, distribution and condition of the ichthyofauna of these areas.
Okeanologiâ. 2025;65(3):532-534
532-534