Vol 59, No 1 (2019)

A model of an advective thermocline is proposed for the case of continuously stratified Sverdrup circulation with a ventilated layer caused by the divergence of flows in the Ekman layer: an immiscible layer with homogenized vorticity and a layer of abyssal liquid, which applies to anticyclonic gyre waters. The results of calculations for the Atlantic Ocean (region 15-52°N, 00-63°E) made with this model are presented. With an abyssal density of 28.0, the values of the surface density and density of the unventilated layer grow to the north from 24.2 to 27.0 and from 27.8 to 27.9, respectively, with an almost zonal distribution, i.e. ventilation zones have latitudinal circles. From calculations of the depths of wind circulation, it follows that the ventilating layer is as deep as 900 m in the north-western region and raises to 250 m in the southern and eastern parts of the basin. The same tendency is traced for the depth of the gyre, but here there is an increase in depth from 500 to 1500 m. The active dynamics in the ventilating layer and the shadow area on the eastern border are noted. The structure of the thermocline is demonstrated with a typical zonal section, characterizing a much larger isopycnic increment for ventilated layers than in non-ventilated layers.

The article provides an analysis of intra- and inter-annual variability of dissolved oxygen and temperature in the upper layer of the deep-water and north-western parts of the Black Sea in the period from 1923 to 2013. The analysis is carried using the archived data from the oceanographic database of Institute of natural and technical systems. Seasonal variability of dissolved oxygen concentration and temperature is out-of-phase. In average, dissolved oxygen concentration is at a maximum at the N-W shelf in winter and is at a minimum in the open Sea in summer. The amplitude of the seasonal variations is about 50 µmol/l. In general, this is consistent with the published results on the seasonal variation in temperature. However, in some periods, lasting about 20 to 30 years, seasonal variation varies. It is due to quasi-periodical interdecadal variability of dissolved oxygen concentration which differs from one season to another and in various subregions.

In this paper, we analyzed data of POI FAB RAS cruise (No. 33) held on «Akademik M.A. Lavrentyev» vessel in the northwestern part of the Japan Sea in May 2004 and compared them with satellite derived data from Climate Change Initiative Ocean Colour (CCI-OC) and Ocean productivity databases. The following in situ data were used for the analysis: CTD-data, assimilation number, nutrients (P, N, Si) and chlorophyll a (Chl). Ship assessments of Chl in the first optical layer were in average 0.5±0.58 mg/m3, while satellite Chl were nearly twice more – 0.95±0.36 mg/m3. Ship assessments of primary production (PP) were 1870±900 mg C/m2day that is 1.5 times larger than satellite derived data - 1226±432. Vertical profiles of nutrients, temperature and Chl showed that main mass of Chl was concentrated in a layer from 20 to 45 m, where the main production is formed. According to values of assimilation number, main production formed in a layer of 0-55 m in the south of the region and 0-30 m in the north. Weak correlation between ship and satellite PP values found in this paper may be explained by low accuracy of satellite derived estimation.

Were found peculiarities of the structure and distribution in the autumn plankton of the South -Eastern part of the Baltic sea (SEB) in October 2015 taking into account hydrological and hydrochemical data. There were no changes registered as to the taxonomic composition of phyto- and zooplankton, including no increase in the number of the stenothermic and stenohaline species, as well as no significant differences in the hydrological parameters in comparison with the long-term analogous data. Thus, there was no influence of the winter Major Baltic Inflow in December 2014 on the plankton SEB next autumn. The level of phytoplankton vegetation in the upper homogeneous layer (125±39 thous. cells/l, 664±143 mg/m³) was higher compared to the long-term data. The abundance and biomass of zooplankton (5.1-16.8 thous. ind/m³ and 49-143 mg/m³) were within the typical value for autumn in the studied area. Peculiarity of zooplankton spatial distribution were related to trophic resources and the thermohaline structure of the water column.

For the first time, a comparative analysis of spatial-temporal changes in macrophytobenthos based on a landscape approach was performed in the Laspi Bay for the period from 1983 to 2008. Landscape maps of the Laspi Bay was created, the distribution of the bottom natural complexes with the key Black Sea phytocoenoses was shown. It was found that the plant components of the bottom natural complexes in the Laspi Bay had undergone significant restructuring and degradation during 25 years due to the impact of natural factors and anthropogenic activities in the coastal zone.

We have revealed the features of similarity and difference in Mesozoic sedimentation history of the East Barents and Sverdrup sedimentary basins based on sea areas, sedimentary masses per time unit and coefficient of the sand content. During the end of Paleozoic and in Mesozoic times both basins have been located near each other but didn’t merged into the one great basin.

Was reconstructed deep-sea water circulation near the Hunter Channel (Rio Grande Rise – South-West Atlantic) in a late Pleistocene and Holocene (MIS 4-MIS 1) by benthonic foraminifera. Was studied three cores of bottom sediment. Now moves the upper North Atlantic deep water (NADW) through the Hunter Channel from the North to the South. The lower NADW in the same direction came in MIS 2 and in MIS 4. There was the lower Circumpolar deep water (CPDW), NADW and Antarctic bottom water (AnBW) in MIS 3 periodically. CPDW prevail in a near bottom layer and in Holocene and in the late Pleistocene before the Hunter Channel sidewise the Argentine Basin. So in the Hunter Channel and on the way to it from south side for all studied period AnBW was almost not. Dissolution of carbonates during the Holocene happens in the deepest east part of the Hunter Channel. In Ice Ages processes of dissolution amplified and affected east part of the channel. Dissolution happen and happened not at the expense of AnBW, and at the expense of NADW which becomes there aggressive in relation to a calcium carbonate.

For the first time, vertical and lateral distribution patterns of mercury in White Sea bottom sediments have been determined. An abrupt change in the nature of mercury concentrations has been revealed, with a general tendency to decrease with depth. Natural variations in mercury concentrations within 0.01 - 0.03 μg/g dry weight (dw) have been established. An upper value of 0.03 μg/g dw is taken for the natural background content of the element. The distribution of mercury concentrations in the sequence of bottom sediments is influenced by both anthropogenic and natural factors and processes. With distance from the marine -estuary boundary of the Northern Dvina River, the river’s role in supplying mercury to the White Sea is reduced, and global and regional atmospheric mass transfer take over. The mercury content is used as an indicator of landslide processes in Kandalaksha Gulf of the White Sea. The accumulation chronology of mercury in White Sea sediments is studied, and the proportion of anthropogenic mercury is calculated.

During the period of 2002–2018, southern Russia was subjected to extreme weather conditions, which can be characterized as drought. The water content and volume of the Don, Kuban, and Volga rivers decreased, salinization of the Sea of Azov was observed, and saline (4–6‰) Azov water periodically flowed into the Don River delta. Analysis of the hydrological observation data for 2018 revealed an episode of extreme flooding in the Lower Don (below the Kochetov hydroelectric complex) associated with the 15-year shortage of water in the body of the Don. An outstanding example of a natural and manmade anomaly in 2018 was the discharge of a significant amount of water from the Tsimlyan reservoir in April–May. For example, the average daily discharge was 345m³/s on April 10, 1503 m³/s on April 28, and 1701 m³/s by May 6. As a result, the maximum wave of water abundance in the Don formed by the end of April–beginning of May 2018, and the water level reached values not observed in the Don for 15 years. The research in the Gulf of Taganrog showed considerable desalinization of its eastern part. The level of salinization in this region did not exceed 2‰, while in spring 2017, the average values of salinization around the port of Taganrog were over 6‰.

The article discusses the results of research on benthos, carried out in south-western Bering Sea using remotely operated vehicle Comanche. The vertical distribution of the dominant animals on the northern slope of the Volcanologov Massif and fauna associated with the hydrothermal vents of Piip Volcano was studied.

The first results of the multidisciplinary expedition aboard the RV «Akademik Mstislav Keldysh» to the North Atlantic in July 2017 are given. Continuation of deep convection in the Irminger Sea to a depth of 1500 m, which began in 2015, is discovered. New information is provided on the structure of the main jets of the North Atlantic Current in the Iceland basin and in the Irminger Sea (Irminger Current), as well as the East Greenland Current. New samples of atmospheric aerosols, suspended particulate matter and bottom sediments are collected. New data on the particle fluxes have been obtained using sediment traps.

In 2017, comprehensive geological, geophysical, hydrological and hydrochemical researches were conducted in the South-Eastern Baltic Sea and the Gulf of Finland. 1775 nautical miles of surveys were conducted using multibeam echosounder and profiler. Surface bottom sediments (156 samples), the upper undisturbed layer of pelitic sediments and bottom water (15 samples), 2 cores were taken. Laboratory analyzes were performed on pH (189), concentration of oxygen (246), suspended matter (286) and oil products (110). Microplastic was also collected in the water (118) and bottom sediments (45). Conducting comprehensive research in the South-Eastern Baltic Sea allowed us to record the weakening of the Major Baltic Inflow effects, followed by changes in the environmental conditions of the region. Geological surveys in the Gulf of Finland expanded the coverage area of the bottom of multibeam surveys and contributed to the refinement of the formation processes of linear and circular transgressions at the bottom.