Okeanologiâ

Based on remote sensing data on the distribution of oil spills obtained using synthetic aperture radar (SAR) imagery of the Sentinel-1A and Sentinel-1B satellites in 2016–2022 and the results of the analysis of aliphatic hydrocarbons (AHCs) and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments taken in 2019–2022, the nature of oil slicks in various areas of the Barents Sea has been established. It is shown that the distribution of oil slicks in coastal areas is greatly influenced by anthropogenic hydrocarbon inflow (mainly from shipping and fishing), which is confirmed by elevated AHC concentrations in coastal sediments (up to 73 μg/g) and in the composition of C_org (up to 3.6%). In the central and northern regions of the Barents Sea (station 7105, in the coordinates 75.2–75.3 N, 31.5–31.8 E), the grouping of oil slicks is due to natural seepage of oil and gas. This is confirmed by the anomalous concentration of PAHs in the lower horizons of the obtained sediment column, and their composition (the dominance of 2-methylnaphthalene, a marker of their oil genesis). At the same time, the proportion of light homologues in the composition of alkanes increased, which may indicate their formation in the sedimentary sequence.

Within the framework of the program “Marine Ecosystems of the Siberian Arctic”, based on the materials collected during the 69th and 72nd cruises of the R/V “Akademik Mstislav Keldysh”, a study of the distribution of a group of chemical elements (As, Ba, Bi, Co, Cr, Cr, Cd, Co, Cu, Cr, Mn, Ni, Pb, Sc, Ti, Tl, Th, V, U and Zn) and organic carbon in the mass taxa of the Laptev Sea macrozoobenthos in the fields of methane seepage and outside them was carried out. For the first time, the bioaccumulation potential (BP) was quantified, taking into account, along with the concentration of elements in organisms, their biomass. At the C-15 methane field, the population of brittle stars accumulates each of the microelements many times (up to 40 times) more than at the background station. Brittle stars and bivalves show increased BP for Ni, As, Ba, Cu, Ti, V, Mn, and Zn compared to other elements, with brittle stars having significantly higher BP. It is assumed that the increased bioaccumulation of some heavy metals and metalloids in methane seep areas is associated with a greater bioavailability of organic matter in bottom sediments. For organic carbon, the highest BP was established, which is especially expressed in the C-15 methane field. At the background station, taxa accumulate a significantly smaller (by a factor of 10) amount of carbon in their biomass. As a result of the functioning of the ground eaters, bottom sediments are enriched with organic carbon, which may indicate an important contribution of benthic organisms to the carbon cycle in the seas of the Arctic.

The content of sediment forming minerals in two cores from the eastern (ANS45-37) and western (ANS45-48) parts of the Vema transform fault valley is studied using the semi-quantitative XRD analysis of bulk powder sediment samples. The mineral composition of deep-sea sediments from the Amazone cone is also analyzed for comparison. It appeared that the average composition of the terrigenous component of both cores (according to prevailing quartz, secondary mica, plagioclase and potassium feldspar, as well as smectite, chlorite, kaolinite, illite) is quite similar and approximately corresponds to the composition of sediments from the Amazon cone. The ratio of four clay minerals suggests the supply of terrigenous material to the Amazon and Orinoco due to the erosion of the Andes and humid tropical weathering in the lower course of the rivers with further transportation of the suspended load to the ocean. This material was transported to the Vema transform valley due to the interplay between the gravity flows from the South American continental slope and the current of the Antarctic Bottom Water. Data on biogenic calcite (planktic foraminiferal tests, nannofossils) and opal A (radiolarians, sponge spicules) are obtained in addition. In the study area, several authigenic (diagenetic) minerals are identified. In particular, siderite and greigite are first found in the sediments from the Vema valley and Amazon cone, respectively.

Rheological layering of a tectonosphere of the South China Sea (SCS) on the crust rigid (the depth interval of 5–30 km), viscous subcrustal (the depth interval of 30–70 km), rigid lower lithospheric (50–90 km), astenospheric (80–150 km) and rigid subastenospheric (the depth interval is more than 150 km) is established. Distributions of the density inhomogeneities connecting with the main tectonic events in SCS are caused by the Paleo-Pacific’s convergence, and later — the Philippine’a oceanic plate with the Philippine archipelago and further — with the Asian margin. In this zone by distributions of density contrast in a tectonosphere are tracing Cenozoic processes of a subduction, stretching, transformic shift and structure of the central type of the probable plume nature which form an evolutionary sequence: back arc, or paleo-oceanic spreading → the Philippine subduction → NE-stretching with shift → formation of the structure of the central type of a probable plume origin. The structures caused by convergence of the Asian continent with the Indo-Australian plate are isolated from the West Pacific margin, and the underthrsting of rigid lithospheric plates from the South under a lithosphere of the margin sea reflects traces of more ancient collision of fragments of the Gondwana with Asian continent.

A five-year observation (2017–2022) of abrasion destruction of rocks in the littoral and upper sublittoral zone of the Dalnezelenetskaya Bay (Murmansk coast) was carried out. During this period, a slow rate of destruction of rocks was observed, not only in the upper sublittoral zone, but also along the entire littoral of the coast. It was revealed that the rate of destruction of coarse-grained material in 2017–2022 averaged 15±3 µm/g. The greatest influence on the intensity of destruction of rocks was exerted by storms generated by winds with a force of 7–12 m/s from the east and southeast directions. It is established that in 2021–2022 there was an activation of abrasion destruction of rocks in the sublittoral zone of the Murmansk coast. Based on the analysis of hydrological, meteorological and seismic data, it is assumed that the activation of the abrasion process was caused by an increase in the number of storm periods, perhaps the tectonic activity of disjunctive structures on the coast played an important role in this. The data obtained indicate that changes in the temperature and salinity of the water mass in the bay do not have a significant effect on the rate of the abrasion process.

The design and principles of operation of the bottom multi-modem station MDS-II, located in the coastal zone (depth of location — 25 m) of the northeastern part of the Black Sea at the Gelendzhik Test Site of IO RAS are described. The station is connected to the coastal center by means of a bottom fiber-optic cable, through which power is supplied to the station, and online transmission of measurement data takes place. The station is an underwater server to which one can connect a measuring device and get a real-time access to it, as well as remotely control on its operation. The design of an automatic stationary station for vertical sounding (SSVS) of water column, which is also used at the Gelendzhik Test Site, is also described. This station is installed close to the MDS-II multi-modem station and is connected to one of its modems. The station consists of a bottom electric winch installed on the seabed and a floating module (probe) on a cable line wound around the winch drum. When the command ʺsoundingʺ is given, the cable unwinds and the floating module, equipped with temperature and pressure sensors, floats and measures the water temperature profile from the bottom layer to the sea surface. Then the cable is winding on a drum, and the floating module returns to the bottom layer. A prototype of a new SSVS is being developed, which will allow sounding of the water layer with a thickness of up to 100 m. It will be equipped with a multi-parameter probe that makes joint measurements of hydrophysical and bio-optical parameters.

Seismotectonic and seismoacoustic studies carried out during the expedition onboard the R/V ʺAkademik Boris Petrovʺ in the Pechora Sea revealed a paleoseismodislocation confined to a fault zone tracing the Severoural seismic lineament. The amplitude of this dislocation (the relative displacement of its sides) makes it possible to estimate the magnitude of the ancient earthquake that occurred within the Severoural lineament. Using the value of this magnitude, estimates were made of the maximum seismic impacts on offshore oil and gas facilities that are already in operation and are being designed for construction in the northeastern part of the Pechora Sea. These assessments of essential images differ in a big way from similar assessments made earlier. The method of searching for paleoseismic dislocations using seismoacoustic methods, as well as lineament analysis, can be used to assess the initial seismic impacts in water areas.