Vol 63, No 2 (2023)

In this study we investigate the impact of variability of the Atlantic Meridional Overturning Circulation (AMOC) on water temperature of the upper 100-m layer of the North Atlantic and Arctic oceans. We use three data-sets (ARMOR-3D, SODA3.4.2 и ORAS4) with different spatial resolution and covering different time periods. The temperature variability is decomposed into its natural modes using Empirical Orthogonal Functions (EOF). The second EOF, which accounts for 20–27% of dispersion of water temperature in the upper ocean, is associated with a change in the AMOC intensity. The time variability of the principal component of this mode has high correlation with the AMOC (0.6–0.9 depending on the data-set and the AMOC index used). The AMOC has the highest impact on water temperature in the Irminger and Labrador seas. The related amplitude of water temperature fluctuations reaches 1.5–2°С in the central part of the Irminger Sea, which is one of the key deep convection regions. Intensification of the AMOC leads to an increase the upper ocean temperature over most of the North Atlantic and Norwegian Sea and to a decrease of water temperature over most of the Greenland Sea, Barents Sea and in an area north of Spitsbergen.

In this paper, we study the effects of strong stretching in the horizontal plane of large-scale mesoscale ocean eddies using the ellipsoidal eddies theory in the World ocean. The purpose of this work is to theoretically determine the physical conditions for unbounded stretching eddies and also check the feasibility of these conditions in the ocean. We estimate the share of mesoscale ocean eddies that are elongated into filaments and then they redistribute energy from the mesoscale to the submesoscale.

Inter-annual (2002–2021) variability of the Kara Sea PP and associated environmental factors was assessed by MODIS-Aqua data and model calculations. Warming in the Kara Sea region during the last two decades was characterized by the pronounced positive trend of surface water temperature (T₀) and weak positive trend of free-ice area (S) averaged for the growing season (April – October). During the investigated period T₀ increased by 3.55°C with a trend of 10% y^–1 and S increased by 110×10³ km² with a trend of 1.4% y^–1, on average. The values of water column PP (IPP) statistically significant (p < 0.05) decreased in the all of the Kara Sea regions (R² = 0.22 – 0.59). For the entire Kara Sea the IPP declined by 38 mgC m^–2 d^–1 with a moderate trend of 1.1% y^–1 (R² = 0.37). The growing season averaged value of photosynthetically available radiation (PAR) weak, but statistically significant (p < 0.05), decreased in the all of the Kara Sea areas (R² = 0.20 – 0.31). Also, in the all regions the significant (R² = 0.24 – 0.38) weak or moderate negative trends of surface chlorophyll a (Chl) were specified. The total annual PP (PP_tot) increased insignificantly in accordance with increase of S (0.7% y^–1, R² = 0.08). The most significant decline of IPP was specified for spring (R² = 0.28). In autumn the statistically significant positive trend of S (R² = 0.24) was observed. Due to such increase of S, the strongest growth of PP_tot was noted in autumn. In the present work was shown that decrease of IPP, resulting from decline of PAR and Chl, was the reason of moderation of PP_tot. Weak increase in PP_tot was observed in autumn and in the north area of the sea. It should be concluded that during the period of intense warming, the decrease in the IPP of the Kara Sea should affect the productivity of the higher trophic levels of the food web.

New data are presented the seasonal changes in abundance, biomass of copepods and fodder zooplankton in areas offshore the Crimea. These investigations are based on the materials of five expeditions of the RV “Prof. Vodyanitsky” in the northern part of the Black Sea and the southern part of the Sea of Azov in different seasons of 2016. It was shown: 1) Seasonal differences in the taxonomic structure of the Copepoda taxocene from the shelf and deep waters were revealed. The warm-water invasive species Acartia (Acanthacartia) tonsa and Oithona davisae were relative numerous in the copepod assemblages on the shelf in summer and autumn. In the deep waters, with a low abundance of warm-water invaders, cold-water native species were dominating, and the structure of the Copepoda taxocene was more stable than on the shelf in these seasons. 2) Zooplankton abundance in 2016 was higher compared to 2010 and the 1990s. The data on zooplankton, supported by information about an increase in the species richness and abundance of fish larvae in recent years, make it possible to talk about the transition of the Black Sea ecosystem to a new, relatively stable state.

The Anapa sandy bay-bar and the territories bordering it occupy one of the leading places in Russia as a recreational sanatorium-resort area, sea tourism and children’s recreation, the role of which as a resort of federal significance has now significantly increased. Unfortunately, in recent decades, areas with progressive erosion have been observed on the seashore of this bay-bar. To substantiate the forecast of further development of the coast and the choice of ways to stabilize it, a number of studies have been carried out, including the determination of sand reserves from which the bay-bar is composed, a number of measures for their conservation have been proposed and potential replenishment opportunities have been considered. The presented work considered and analyzed the results of geophysical studies on the marine underwater coastal slope of the Anapa bay-bar, first performed to assess the volume and distribution of wave field sand deposits within the coastal zone as a possible source of beach formation and, accordingly, an increase in the volume of sand in the bay-bar as a whole.

The paper provides the first lithology and age data from the Ameghino segment of the Atlantic Patagonian Margin. The multi-proxy study, including lithology, microfossils, magnetic susceptibility, color reflectance and accelerator mass spectrometry enables the litho- and chronostratigraphic frame of the six short (<1 m) sediment cores from the continental margin from the water depth range of 2–2.3 km. The units corresponding to marine oxygen-isotope stages (MIS) 1–3 are identified and distantly correlated with the simultaneous units of the reference core AI-3327 from the Piedra Buena Terrace. The unit thickness and sedimentation rates are evaluated. The occurrence of glauconite in the coarse-grain sediments of the last glacial, previously described from the simultaneous sediments on the Piedra Buena Terrace, is confirmed now within the Ameghino segment of the continental margin. The confirmation of the contourites occurrence in the sediment cores is also provided suggesting the bottom currents involvement in sedimentation.

89 cruise of R/V “Akademik Mstislav Keldysh” was organized by Shirshov Institute of Oceanology in a frame of the Program “Marine Ecosystems of Siberian Arctic” and was held form 19 September to 10 October 2022. 60 scientists from the institutes of Russian Academy of Sciences, Moscow State University, Moscow Institute of Physics and Technology, VNIRO and MES participated in the cruise. Coordinated hydrophysical, hydrochemical, biooceanological, geochemical research, valuation of greenhouse gases concentration in above-water atmosphere were carried out over the shelf and continental slope of the eastern poorly known part of the Kara Sea. Ecosystem of Blagopoluchiya Bay (Novaya Zemlia) and conditions of disposals of radioactive waste in the bay were in a focus of the research as well.

We provide information on geological and geophysical studies of the structure of the Mid-Atlantic Ridge between the Charlie Gibbs and Maxwell transform faults in the North Atlantic during the 53-th cruise of the R/V Akademik Nikolaj Strakhov in July–August 2022. The preliminary results of the expedition are discussed.