Spatial variations of nutrients along the northwestward stream from Bering Sea to Chukchi Sea are considered for dissolved inorganic phosphorus (DIP) on the data of two surveys conducted in early September of 2010 and 2020. The waters of Bering Sea origin have higher DIP than the waters of Chukchi Sea, but in the upper layer gradually loose phosphorus because of both mixing with local waters and consumption for photosynthesis. In the subsurface layer, the DIP decreasing is prevented by its recycling from destructed organics. The fluxes of phosphorus are estimated separately using the balance model with TS-analysis, previously used in estuarine studies. Successive utilization of DIP along the stream is traced, that forms in the Chukchi Sea two zones of high productivity divided by wide low-productive zone. The nutrients from the upper layer are utilized within the southwestern Chukchi Sea providing primary production 0.1–0.2 gC/m3day, but the main stock of allochtonous nutrients from the subsurface layer is utilized further downstream (at Wrangel Is. or in the northern Chukchi Sea) and provides the production of 0.3–0.4 gC/m3day. Localization of the high-productive zones is determined by density stratification that possibly depends on the stream strength: the stronger advection through Bering Strait – the further from the strait both zones are located. Recent tendency of the stream strengthening tends to remove the zones of utilization the nutrients of Pacific origin out of the southwestern Chukchi Sea.
92d cruise of R/V “Akademik Mstislav Keldysh” was organized by Shirshov Institute of Oceanology in a frame of long-term Program “Marine Ecosystems of Siberian Arctic” and was held from 5 October to 7 November 2023. 76 scientists from the institutes of Russian Academy of Sciences, National Research Center Kurchatov Institute, Moscow State University, Moscow Institute of Physics and Technology, VNIRO and MES of Russia participated in the cruise. Coordinated hydrophysical, hydrochemical, biooceanological, geochemical research were carried out in the eastern part of the Kara Sea in the period of seasonal ice formation, as well as in the Ob river estuary and fjords of Novaya Zemlya archipelago. Conditions of largest disposals of radioactive waste in the Kara Sea were evaluated.
The ice-gouging topography of the southwestern part of the Kara Sea bed is a result of the impact of icebergs and sea ice. During 52 cruise of the R/V Akademik Nikolaj Strakhov using a multibeam echo sounder we collected a representative data of key parameters of ice scours (location, orientation, depth, width) for the first time, which allows us to draw conclusions on a regional scale. We revealed regularities in the distribution of the ice scours both in space and in depth and their density in different parts of the seabed. It was revealed that the maximum dimensions of the ice scours decrease with the distance from the sources of iceberg calving from NW to SE. The orientation of the ice scours correlates with the main drift directions of the icebergs. Most of the ice scours are located at depths up to 220 m and could have formed both at modern and at lower sea level (in post-glacial time). We identified a high degree of the seabed transformation by ice-gouging processes in the southwestern part of the Kara Sea.
Brief results of expedition investigations of the southeastern part of the Baltic Sea and the eastern part of the Gulf of Finland during the 53rd cruise of the R/V Akademik Boris Petrov (2023) are presented. The expedition was dedicated to continuation of longstanding oceanological researches conducted by the AB IO RAS. An integrated geological, geophysical, hydrological, hydrochemical, hydrobiological and geoecological investigations were carried out. New data on the state and dynamic of natural systems of the Baltic Sea were obtained.
This report is devoted to the analysis of original geological materials on the Magellan Seamounts in the Pacific Ocean, obtained by the authors in numerous voyages of R/V ʺGelendzhikʺ. This chain of guyouts does not have a common volcanic basement and apparently was formed in the second half of the Early Cretaceous on the oldest (middle-last Jurassic) fragment of the Pacific plate. The main points of view on the genesis of the Magellan Mountains are as follows: either they originated at the crossing of the transform fractures, or the Pacific plate moved them from the southern hemisphere to their present-day position. Because of their high degree of study, the Magellan Seamounts are one of the key sites for understanding the mechanism of the origin of linear chains in the ocean. A comprehensive analysis of new geological on the Magellan Seamounts has established the important role of magmatism and tectonics in the formation of the modern morphological shapes, sedimentation and influence on the paleooceangraphy. The periodic renewal of these processes from the Early Cretaceous to Late Cenozoic can be traced in the cyclicity of sedimentation, the permanent growth of ore crusts and the formation of secondary volcanic domes and cones.
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.
In order to explain the spatial nature of the distribution of eelgrass in the inner bays of Posyet Bay, numerical experiments were performed to simulate hydrodynamics and morphodynamic processes. The hydrodynamics was modeled using the Delft3D Flow model. The spectral wave model SWAN (Simulating WAves Near shore) was used to calculate the wind wave parameters (propagation direction, wave length and height, near-bottom orbital velocities). Alteration of coastal zone profile under the impact waves and the hydrodynamic of tidal and wind currents was performed using the Delft3-MOR morphodynamics module included in the Delft3D software package. The results of numerical experiments have shown that the dynamics of the coastal bottom topography is determined by sediment transport forced by combined action of waves and currents. Comparison of the modeling results with information on the distribution of Zostera of previous studies and field surveys data showed a high agreement with model data on the spatial distribution of erosion and accumulation zones in the coastal zone.
Currently, most seashores are experiencing increased erosion and retreat. To a large extent, this applies to coasts subject to the influence of high-amplitude sea tides, which is extremely negatively manifested on the accumulative coasts of oceanic islands. The solution of the problem of their dynamics, the theoretical foundations of which are still in the development stage, can be based only on the basis of wide-regional studies. This work is aimed at elucidating the features of the dynamics of such a coast using the example of a key region of a large oceanic island. The main reasons for its degradation are identified, recommendations are given for stabilizing the coastline, and the development trend according to the natural scenario is considered.
Data on the structural and production characteristics of bacterioplankton in the western part of the Kara Sea at the beginning and in the middle of summer are presented. In the region of the St. Anna Trough slope, the average abundance of prokaryotes for the water column was (594–708) × 103 cells/ml (26.4–36.5 mgC/m3) in June and (247–517) × 103 cells/ml (12–28 mgC/m3) at the beginning of August. On the transect along Novaya Zemlya, the average abundance of bacterioplankton in the water column was (186–554) × 103 cells/mL (8.5–30 mgC/m3) within a week after the seasonal ice and (169–443) × 103 cells/mL (8–21 mgC/m3) in the midsummer. Bacterial specific growth rate did not exceed 1.28 day–1; its high values were observed in the upper warm water layer, above the halocline, and also at the near-bottom depths. At the beginning of summer, the production of bacterioplankton tended to decrease in the northeast direction. The distribution of prokaryotes abundance was determined by temperature and water saturation with oxygen, possibly as an indirect indicator of past phytoplankton “bloom”.
The principal basins on the Mozambique continental margin are the Mozambique and Rovuma, on the passive continental margin with complex tectonic history, following after the East African Rift System in the Triassic. Although the first gas fields in the coastal zone of the Indian Ocean in southeast Mozambique are appeared yet in the 1960s, only in 2010, did Mozambique achieve a new status as a major world hydrocarbon player—with the discovery of a number of large gas fields in the northeast of the country, in deep-water regions of the Indian Ocean, and in the Rovuma Basin. More than 20 recently discovered gas fields are located in deep-water regions and on the continental slope of the Indian Ocean at depths of 468–2610 m. It is noteworthy that the pays of the same age, the deeper they are buried beneath the water column, the greater their volume of hydrocarbon reserves. A similar trend may help in the case of targeted oil and gas exploration. The prospects of liquid hydrocarbon discoveries are possible in the Madagascar channel behind the Davie Ridge and in deep-water parts on the slopes of the Mozambique continental margin.
The first quantitative video survey of the benthic megafauna was carried out on a transect in the eastern part of the Kara Sea from the slope of the Voronin Trough to the upper shelf in the depth range from 1680 to 70 metres. The data were obtained using the TUV “Videomodule” during the 89th cruise of the R/V Akademik Mstislav Keldysh in autumn 2022. It was shown that the megabenthos in this area differs significantly from that of the western part of the sea and Blagopoluchiya Bay (Novaya Zemlya). In the eastern part of the Kara Sea, echinoderms dominated, among which ophiuroids were in the first place, whereas in the western part of the sea and the Blagopoluchiya Bay, the key component of the megafauna was the snow crab Chionoecetes opilio. Single adults of Ch. opilio were recorded for the first time at almost all stations in the eastern part of the sea, but, in contrast to the western area, the snow crab has not yet become dominant here and has not influenced the benthic communities.
The dependence of the respiration rate (R) on an animal’s weight (W) is described by the equation R = aW b, where the exponential coefficient b is usually taken equal to 3/4. However, several authors have indicated that the value of coefficient b may vary with temperature changes, as well as during ontogeny. In Arctic seas, copepods spend most of their lives at temperatures below or close to zero. Meanwhile, there are very few respiration rate measurements at temperature ≤ 0°C, which does not allow us to estimate the value of coefficient b at subzero temperature. The study was carried out on three cruises of the R/V Akademik Mstislav Keldysh in the Siberian Arctic seas in 2018–2020. Copepods caught from the sea were adapted to the experimental temperature and placed in tightly capped vials filled with filtered seawater for 24 h. The oxygen concentration was measured with a fiber-optic oxygen probe. The results of 120 respiration rate measurements and 111 body carbon measurements in five species of copepods at a temperature of –1.5°C are presented. The obtained relationship between body carbon content (W) and prosome length (L) is described by the equation W = 6.982L3.221, and the dependence of respiration on body weight is described by the equation R = 0.077W 0.753. No effect of subzero temperature on coefficient b was revealed. The parameters of regression R(W) did not change with the ontogenetic development of Calanus glacialis.
The isotope parameters and sources of freshwater components for the subsurface, intermediate, and deep water of the western Bering Sea were estimated using the isotope (δ18О, δD) data for 177 seawater samples. We show that subsurface, dichothermal and, partially, intermediate water (<1000 m) are freshened by regional precipitation. For these waters, the next equations of relations between delta and salinity values were obtained: δ18О = [0.390 ± 0.018]S – 13.521 ± 0.613 and δD = [3.07 ± 0.08]S – 107 ± 2.74. Deeper (1000–2500 m) water is also freshened by precipitation but from the more southern region (≈40°–45° S). The deepest water (2800–4300 m) retain their isotope signal obtained via freshening by Antarctic glacier ice meltwater. The distribution of isotope parameters with the depth shows that vertical mixing at depths of ≈1000–2500 m takes place. This process should influent the redistribution of nutrients, dissolved oxygen, organic matter, and other components in water of the western Bering Sea. The isotope composition of water passing into the Arctic Ocean halocline (S = 33.1) from the Bering Sea are δ18О = –0.61‰ and δD = –5.4‰.
Based on the results of an analysis of 174 samples of bottom sediments collected at 48 stations in the Chaun Bay during the cruise 60 of the R/V Akademik Oparin (October 2020), it was found that their grain size distribution varies from poorly sorted silty clay to well sorted sand. The results of the study led to conclusion that the main sedimentation mechanisms in Chaun Bay are thermal abrasion, river runoff, and abrasion, as well as ice rafting and aeolian transport. The zoning of grain size types of bottom sediments is related to the bottom topography and consistent with areas affected by riverine runoff, abrasion, and thermal coastal abrasion, as well as with the direction of currents. The high occurrence of coarse clastic matter in sediments is evidence of abrasion of the coastal zone and active ice rafting of large (up to 15 cm) rock fragments. The vertical variability of the grain size parameters of the studied bottom sediments within the upper 20 cm layer reflects gradual Late Holocene intensification of terrigenous (fluvial and thermal abrasion) fluxes with the current effects of climate change in the Arctic.
The field data on the abundance, biomass, age structure, and lipid reserves of the copepod Сalanus euxinus population in deep pelagial and Crimean shelf regions of the Black Sea in November 2017 were analyzed. The abundance and biomass of this species in deep areas (10.2 ± 0.5 × 103 ind./m2 and 7.3 ± 0.5 g/m2, respectively) were similar to the average annual values for seasons with moderate development of planktivorous jellyfish populations. The average abundance and biomass of the copepods were similar to analogous 2016 values when the jellyfish abundance was twice as low. However, in 2017, the denser aggregations of C. euxinus (12.8 ± 1.0 × 103 ind./m2 and 9.8 ± 0.5 g/m2) were found in the central parts of cyclonic circulations, while in 2016, they were recorded more frequently at the peripheries of cyclonic gyres. A structure of the C. euxinus population also changed. In November 2017, the percentage of copepodites I–IV, females and males, increased, whereas the proportion of copepodites V reduced. These changes likely resulted from a later sampling period in 2017, when the C. euxinus population was ready for active reproduction. Sufficient amounts of lipids in copepodites V, decreased oil sac volumes in females, and increased abundance of males in anticyclonic regions are indicative of more favorable trophic conditions for this part of the C. euxinus population and its higher maturity.
Based on contact data, the dynamics of the abundance (N) and biomass (B) of phytoplankton in 2013–2014 and the concentration of chlorophyll a (Cсhl) in 2000–2003 and 2008–2021 were analyzed using fast Fourier transform (FFT) under conditions of changing water temperature (T) in the vicinity of Sevastopol in the Black Sea. Estimates of the contribution made by the variability of the annual and semiannual harmonics of N, B, Cchl, T to the seasonal cycle amounted to more than 56
This article continues and generalizes the study “On the Similarity of Quasi-Geostrophic Vortices against the Background of Large-Scale Barotropic Currents” [6] (Oceanology, Zhmur, 2024, in print). In continuation of [6], a similar formulation is considered, but for other types of background currents. In the quasi-geostrophic description for small Rossby numbers, the problem of the evolution of an arbitrarily shaped liquid volume with homogeneous potential vorticity of all vortex core particles in an equidistant background flow—horizontal flow with vertical shear and equidistant flow with barotropic and baroclinic components—is presented. Ultimately, the problem boils down to an integrodifferential equation for the evolution of the vortex core boundary. The study of this equation in dimensionless form makes it possible to find a set of dimensionless parameters that determine the similarity condition of the studied vortices.
During cruise 89 of the R/V Akademik Mstislav Keldysh in September–October 2022, search for the snow crab Chionoecetes opilio were conducted in benthic communities of the Kara Sea using a Sigsby bottom trawl and the TUV Videomodule; as well, plankton samples were collected with a Bongo net in order to record crab larvae in the water column. Single large individuals of snow crab were found for the first time in the eastern Kara Sea, on a transect from the Voronin Trough towards the coast of Taimyr, starting at a depth of 490 m. At the same time, not a single crab larva was caught, which indicates penetration of mature crabs into these areas across the bottom. Conversely, in the western part of the sea and in Blagopoluchiya Bay, large numbers of all size groups of C. opilio on the bottom, as well as crab larvae in the water column, were observed. The differences in the speed and nature of the snow crab invasion are explained by the contrast in the ice conditions in the western and eastern Kara Sea. The snow crab population is likely to spread further in the eastern Kara Sea due to trends towards an increase in the ice-free period in the Arctic.
Currently, there are no remote methods for recording the instantaneous two-dimensional profile of the sea surface Z(x, y, t) in field conditions, nor are there any methods for recording capillary wave profiles directly on the sea surface. The short-wavelength component of sea waves plays a very important role in radiometry in the formation of the surface’s own radiation and in solving inverse radar problems. This article proposes an optical measurement technique that can measure the parameters of the entire wave spectrum, including capillary waves with amplitude of less than 0.1 mm. However, the author has not yet been able to fully solve the inverse problem of reconstructing the two-dimensional wave profile. The author considered it expedient to formulate this problem and involve the scientific community in its successful solution. Obtaining the profile of sea waves Z(x, y, t) in natural conditions with a high update rate will yield complete information about the characteristics of waves, temporal and spatial spectra of elevations, spectra of slopes; it will also be possible to study the evolution of waves when the wind changes. The possibility of recording and studying the short-wavelength components of waves, including capillary waves, is of particular value.
The article presents the results of hydrochemical studies of waterbodies with varying degrees of development of anaerobic conditions (up to the appearance of meromixia with sulfide anoxia) in the Porya Guba Bay (Kandalaksha Bay, White Sea, Kandalaksha State Nature Reserve). It is shown that these waterbodies, which are at different stages of isolation from the sea, have a unique hydrological and hydrochemical structure, formed at a certain stage of their evolution. The vertical stratification of water, with the development of all phenomena accompanying stagnation, is more pronounced in the most distant parts of their water area from the sea, where elevated contents of hydrogen sulfide (up to 16.5 mg/L), phosphates, silicon, nitrite, and ammonium nitrogen are noted in bottom anaerobic water. However, the concentrations of all major ions are comparable to those in seawater and hardly chance at all vertically. Analysis of the distribution of the hydrochemical parameters of the distant reaches of Ozerki Lagoon made it possible to conclude that, due to changes that have occurred with this waterbody over the past 90 years, it can now most likely be classified as meromictic.
