Vol 65, No 2 (2025)

Capillary waves on the sea surface have a significant effect on the scattering of both optical and microwave radiation. Although the amplitude of capillary waves is fractions of a millimeter, the slopes formed on capillary waves often exceed 30°, which leads to a strong change in the effective reflection, absorption, and backscattering cross sections. Capillary waves are studied in detail in pools; however, in natural marine conditions, they could only be measured indirectly, usually by reflections or glare. In this paper, a remote method for measuring slopes, amplitudes, and direction of the wave vector of the capillary wave structure in natural conditions is proposed and applied. In the proposed method, distortions of laser beams falling from top to bottom on the sea surface are recorded on a video camera. The authors managed to solve the inverse problem of calculating all the parameters of a capillary wave based on the shape of a capillary comb in video frames. The sensitivity of the method for measuring the wave amplitude is 30 µm at a distance to the surface of over 4 m.

Fluorine concentrations and F/Cl mass ratio values were determined in 40 samples of surface waters of the Indian and Atlantic oceans, and of the Red and Mediterranean seas. A weak trend of increasing F/Cl ratio with chlorine (salinity) increase was established, which in absolute value slightly exceeds the measurement error. An assumption was made about the influence of atmospheric aerosols influx and calcium carbonate precipitation on the fluorine content and F/Cl ratio in the surface horizons of the water column.

During the 89th cruise of the R/V Academic Mstislav Keldysh in 2022, sediment columns were sampled at stations 7441 and 7444 located in the southwestern part of the Kara Sea. Station 7444 was located on a large submeridional depression, under the bottom of which gas-saturated sedimentary strata were detected. Background station 7441 was located at a distance of 68 km from station 7444. For the sediments of the background station 7441, the ratio of hydrocarbon gases C₁ / C₂₊ < 100 indicated their thermogenic nature. In the sediment at station 7441, the formation of the gas component in the sediment was due to degradation of OM and inflow of thermogenic gases, while in the sediment of station 7444 there was an inflow of biogenic gas, apparently, from permafrost. The average concentration of CH₄ in the sediment of station 7444 exceeded the average concentration in the sediment of column 7441 by 700 times, and the average concentrations of CO₂ in the sediment of stations 7444 and 7441 were comparable. A sulfate-methane transition zone (SMTZ) was detected at the 541–545 cm horizon of the sediment of station 7444, where sulfate concentration decreased to minimum values, CH₄ and CO₂ concentrations reached maximum values. The sulfur isotopic composition of δ³⁴S in this region was +20.8‰. The biogenic nature of gas in the sediment of station 7444 was evidenced by low values of the carbon isotopic composition of CH₄ (mean value δ¹³C(CH₄) = –99.7‰), and high C₁ / C₂₊ > 10000 ratio near the SMTZ.

Mogilnoe Lake is a representative of little-studied meromictic water reservoir beyond the Arctic Circle, which has an underground connection with the Barents Sea. This paper presents some aspects of the ecological state of the lake using data on the distribution of sulfur compounds (as a marker of the intensity of anaerobic processes in water reservoir), redox-dependent chlorophenolic compounds, and organochlorine compounds from the group of persistent organic pollutants in bottom sediments and soils of the lake's catchment area. The progression of hydrogen sulfide contamination of lake waters observed throughout the 20^th century has been confirmed: an increase in hydrogen sulfide concentrations in the monimolimnion (210 mg/l) and an increase in the boundary of its distribution are observed. The content of reduced sulfur compounds and the features of their distribution in sediments of Mogilnoe Lake are comparable to those in bottom sediments of marine water bodies with euxinic anoxia. It has been shown that the presence of organochlorine compounds (including persistent organic pollutants) in bottom sediments and soils of catchment area of the lake can be associated not only with transfer by air and water flows, but also as a result of anthropogenic/technogenic impact on the lake in the 20^th century.

Until recently, the Kara Sea was a relatively stable ecosystem unaffected by alien species, but in the early 21st century the Arctic shelf was invaded by the snow crab Chionoecetes opilio. This predator has a wide dietary range and can feed on echinoderms, especially ophiuras, molluscs, polychaetes and crustaceans. This article reports data on the study of benthic communities of the southwestern Kara Sea, based on the materials collected in 2014 and 2019 (before and after the mass appearance of the snow crab). The period of 2014–2019 was marked by significant changes in the structure of benthic communities, while abiotic parameters (near-bottom temperature, salinity and sediment characteristics) remained almost constant at the investigated stations. The most significant changes affected the megafauna. The total abundance and biomass of the megabenthos decreased, the abundance of dominant species also reduced, and the species structure became more even. Most likely, the observed transformation of the benthic communities is related to the establishment of the snow crab, the most affected were dominant benthic species, which are the main prey items of this crab.

During the expeditions of the Institute of Oceanology of the 38th and 41st voyages of the RAS R/V Academic Nikolai Strakhov (2018–2019) in the Pechora Sea between the Kanin Peninsula and Kolguyev Island. Kolguyev revealed a large number of accumulative sandy bottom landforms and characterized a number of their parameters. In 2022 (51st cruise of the R/V Academic Boris Petrov), the study of such relief was continued in order to clarify the area of their development, morphology and dynamics.

The mosaic-block structure of the intraplate deformation area in the Central Basin of the Indian Ocean is confirmed by multibeam bathymetry data collected in cruise 42 of RV Academic Boris Petrov and cruise SO258 of RV Sonne. It consists of a set of isometric deformed tectonic blocks. The linear blockat 0.2–0.6°S, which looks in plan like a stairs or branch, is sharply distinguished by its morphology. This block is a system of multi-scale structural elements (folds, flexures, breaks) that constitute a structural paragenesis formed in the mechanical environment of a right-sided simple shift, and can be interpreted within the framework of the Riedel model.

Cruise 95 of R/V Academic Mstislav Keldysh was organized by Shirshov Institute of Oceanology in a frame of long-term Program “Marine Ecosystems of Siberian Arctic”. The cruise was focused at evaluation of the processes in the Arctic ecosystem in the period of seasonal ice breacking and was held from 21 June to 24 July 2024. Coordinated hydrophysical, hydrochemical, biooceanological, geochemical research were carried out under different sea ice conditions in the central part of the Kara Sea in latitudinal range from 74°30.0ʹ to 80°22.5ʹ N, as well as in the eastern part of the Barents Sea. 62 scientists from the institutes of Russian Academy of Sciences, Moscow State University, North Arctic Federal University, Baltic Federal University, Moscow Institute of Physics and Technology, and VNIRO participated in the cruise.

We provide information on the geological and geophysical studies of the structure of the King’s trough, located on the eastern flank of the Mid-Atlantic Ridge in the North Atlantic Ocean during the 55th and 57th expeditions of the R/V Academic Nikolay Strakhov in 2023 and 2024. Preliminary results of the expeditions are discussed.