SEA-LEVEL PRESSURE TRENDS IN THE SOUTHERN OCEAN AND ANTARCTICA FROM REANALYSIS AND IN SITU DATA

Trends in the mean sea-level pressure (SLP) in Antarctica in the last four decades (1980– 2020) have been examined using in situ observations and reanalysis data. The analysis involved time series of monthly mean, season-mean and yearly-mean values of the SLP derived from four reanalysis datasets, NCEP/NCAR, ERA5, JRA55, MERRA2, and from surface observations acquired from the Reference Antarctic Data for Environmental Research (READER) dataset. With this data we have evaluated the trends, characterized their seasonal peculiarities and variation across the high-latitude region of the Southern Hemisphere. The results of the analysis confirmed the dominance of decreasing trends in the annual mean SLP in Antarctica. Larger negative trends were found in the Western Antarctica with the most pronounced pressure drop in the South Pacific. The long-term decrease in the annual mean SLP in Antarctica was due to strong negative pressure trends in the austral summer and fall season whereas in winter and in spring the trends turn to mixed and mostly positive. The comparison of multiyear time series of SLP reanalysis data with in situ observations at Antarctic stations revealed a considerable overestimate of negative SLP trends in the NCEP/NCAR dataset. Among the four examined reanalysis datasets, ERA5 provided the best agreement with the station data on the annual mean and monthly mean SLP trend values.

IN MEMORY OF VERA BORISOVNA VOZZHINSKAYA

On July 29, 2021, just 90 years have passed since the day of birth of Vera Borisovna Vozzhinskaya, doctor of biological sciences, head of the Laboratory of biological foundation of mariculture IO RAS. She was connected with our Institute during all her life, 43 years – from young post-graduate up to well-known algologist, specialist in benthic marine algae. She was a bright personality, outstanding organizer, skilled expedition worker. Under her leadership 37 coastal expeditions of IO were carried out – to the White, Barents, Black and Far East Seas. She tragically perished in happy and long-awaited moment: just after the authorization of her degree (doctor of biology) by All-Russian Attestation Commission. Publications by V.B. Vozzhinskaya are in demand up to now, especially her unique monograph on the White Sea macrophytobenthos and investigations on productivity of bottom seaweeds.

DETECTION OF RED SEA AND PERSIAN GULF WATERS IN THE NORTHWESTERN PART OF THE INDIAN OCEAN BY ARGO FLOATS DATA

Peculiarities of the spatial distribution of the Red Sea and the Persian Gulf waters in the northwestern part of the Indian Ocean have been investigated based on the Argo float measurement database. 27128 profiles of temperature and salinity were taken into account. To process these data, we used the Argo Model for Investigation of the Global Ocean (AMIGO). This technique allowed us for the first time to obtain a complete set of oceanographic characteristics up to a depth of 2000 m for different time intervals of averaging (month, season, years). Joint analysis of the variability of hydrological characteristics within the depths of 0-500 m during the summer monsoon clearly showed the influence of the Somali Current on the dynamics of the waters of this region: the formation of the largest anticyclone (Great Whirl), coastal upwelling zones, redistribution of water masses in the Gulf of Oman and the Arabian Sea. The main influence on the formation of the temperature and salinity fields is exerted by the Persian Gulf waters. The same analysis of the variability of fields within the depths of 600-1000 m showed the role of the outflow of the Red Sea waters from the Gulf of Aden in the formation of deep waters in this area during the year. And, finally, at depths of 1000-1500 m, a deep anticyclonic eddy is formed, the southern branch of which, moving westward, at 7˚N. reaches Africa and turns to the south with a narrow stream of Red Sea waters, and then, crossing the equator, reaches 15˚S. An original result was obtained for determining the temporal characteristics of the Somali Current: the time of its formation, the values of transports and life expectancy (according to model estimates of the estimated data for 7 years (1960–1996).

TO THE 90TH ANNIVERSARY OF IVAR MURDMAA

On August 6, 2021, the chief researcher of the IO RAS, Doctor of Geological and Mineralogical Sciences, Professor Ivar Oskarovich Murdmaa turned 90 years old. The main focus of I.O. Murdmaa is the study of bottom sediments of seas and oceans, their lithology, mineralogy, deposition processes, facies and formations, the theory of oceanic sedimentogenesis. He first distinguished marine volcanoterrigenous sediments and described the facies variability of modern sediments of island arcs. Ivar Murdmaa is known for his studies in mineralogy of oceanic sediments, processes of pelagic sedimentogenesis and associated iron-manganese nodules formation. Studying sediment formation in rift zones of mid-ocean ridges, he identified a new genetic type of sediments named edaphogeonus sediments, elaborated mineralogical criteria for their recognition and formation processes. In recent years I.O. Murdmaa is actively developing the theoretical concept of "sedimentosphere", paying special attention to a new direction – the study of the erosion-accumulative activity of bottom currents and the formation of contourites.

COMPARISON OF TWO DATA ASSIMILATION METHODS USED TO ACCOUNT FOR OPEN BOUNDARIES IN SEA AREA HYDROTHERMODYNAMICS MODELING

The problems of modeling hydrothermodynamics of particular sea and coastal areas are of current interest, since the results of this modeling are often used in many applications. One of the methods allowing to take into account open boundaries and bring the simulation results closer to real data is the variational assimilation of observational data. In this paper the following approach is considered: it is supposed that there are observational data at a certain moment in time; the problem is considered as an inverse problem, in which the functions of fluxes across the open boundary are treated as additional unknowns. Comparison of methods for reconstructing unknown functions in boundary conditions at an open boundary using sea level and velocity observational data in a number of numerical experiments for a region of a simple shape is carried out.

THE INTRAPLATE VOLCANO-TECTONIC ACTIVITY IN NORTH-EASTERN AND SOUTH SECTORS OF THE PACIFIC LITHOSPHERIC PLATES WITH THE CONNECTION OF THE CHANGE OF ITS RELATIVE MOTION

The analysis of altimetric data in combination with bathymetry and gravimetry materials in the north-eastern and southern sectors of the Pacific Ocean, as well as detailed data on the underwater relief, the structure of the sedimentary cover, the composition and absolute age of basalts obtained within the area of domestic geological exploration for ferromanganese nodules (the Clarion-Clipperton zone) is carried out. Structural trends formed by local cone-shaped local structures of presumably volcanic nature, grouped along transform faults belonging to various stages of the kinematics of the Pacific Plate, have been traced in the structure of the oceanic lithosphere at various scale levels. The first trend corresponds to the extension of the fault system corresponding to the spreading system on the crest of the East Pacific rise before the restructuring of its planned geometry in the Paleocene-Eocene, the second coincides with their extension after the change in the relative movement of the Pacific Plate. The trends are characterized by planned disagreement, and an increase in the number of seamounts is observed in the areas of their intersection. Within the area of detailed studies, obvious signs of volcanic-tectonic activity were revealed: high dissection of the underwater relief, hills of different heights with steep slopes, whose volcanic nature is confirmed by differentiated basalts raised from their slopes, the absolute age of which indicates the multistage outpourings that occurred in an intraplate environment. The angular velocity of rotation of the spreading axis and the linear velocity of its advance with changes in the kinematics of the Pacific plate are estimated and possible reasons for changes in its relative motion are considered. An improved scheme of adaptation of the spreading zone to a change in the direction of relative plate movement is proposed, acc0ording to which an essential factor of intraplate volcanic-tectonic activity is the relaxation of stresses in the plate caused by external influence on it.

LEV IVANOVICH MOSKALEV IN THE MEMOIRS OF RELATIVES, FRIENDS AND COLLEAGUES

This is not a regular journal publication and not just «memoirs». These are sketches written by different authors but all about the same person – Lev Ivanovich Moskalev. On the 4th of December 2021 it will a year since Lev Ivanovich has left us. Relatives, friends and colleagues of Lev wrote about him. Everyone in his own way and everyone about his own. In the mosaic of these sketches, various features and sides were captured of Lev Moskalev, the bright person who has left a deep impression on many of his contemporaries.

ON THE PECULIARITIES OF THE STRUCTURE OF THE MULTIDECADE OSCILLATION OF THE WORLD OCEAN

One of the most remarkable peculiarities of the modern climate, undoubtedly, should be recognized as the climatic shift observed in the mid-70s of the last century. The reasons for this phenomenon for a long time, despite the activation of climatologists from all over the world, remained a mystery that requires its disclosure. First of all, this was due to the fact that the shift that took place turned out to be unexpected for scientists and was accompanied by rapid qualitative changes in the planetary climate. To date, thanks to the efforts of scientists using the results of rapidly developing numerical modeling, diagnostic calculations and observational data in large hydrophysical experiments in various regions of the World Ocean (WO), an understanding of the role of the ocean factor in the variability of the current climate has developed. It became clear that climatic shifts are an important feature of the internal dynamics of the climate system. The most obvious evidence of intrasystemic processes should be considered the discovered planetary structures in the atmosphere – Global Atmospheric Oscillation (GAO) and in the ocean – Multi-decadal Oscillation of the Heat content in the Ocean (MOHO), which are quasi-synchronous accompanying variations in the modern climate. GAO, its structure and features have been discussed in detail earlier in a number of studies. As for the MOHO, its structure and features are discussed in the proposed work. It is characteristic that the MOHO is located in the layer of the main thermocline (100-600 m). In a quasi-uniform layer (0–100 m), and in a deep layer (600-5500 m), the thermodynamic regime differs from the regime in the layer of the main thermocline. Probably, it is precisely this circumstance that did not allow earlier to draw attention to such an important detail in the structure of the WO thermodynamic variability. The presence of extreme multi-decadal temperature field disturbances at intermediate levels (200, 300, 400, 500, 600 m) should be noted as an important characteristic feature of the oscillation. Large-scale hydrophysical experiments (POLYGON-70, POLYMODE, etc.) made it possible to reveal the vortex structure in the dynamics of WO waters and to discover that the vortices of the open ocean have maxima of kinetic energy precisely in the layer of the main thermocline. This allows us to assume a connection between synoptic eddy activity and MOHO. However, the latter remains to be studied.

ON THE OCCASION OF THE 90TH BIRTHDAY OF PROFESSOR IGOR IVANOVICH VOLKOV (1931–2008)

The article is dedicated to the 90th anniversary of the birth of Igor Ivanovich Volkov, an outstanding chemist and geochemist, professor, Honored Scientist of the Russian Federation. His biographical data, his path in science, the main stages of the research, his main scientific works and the people around him are presented.

«CHERNOMOR»: TO THE 50th ANNIVERSARY OF THE LONGEST EXPERIMENT

The work is devoted to a brief description of the preparation and conduct series of scientific experiments in the underwater laboratory “Chernomor” during the period of 1967–1972. The experiments were carried out at the depths from 8 to 30 meters. The place of the experiments is the Southern Branch of the Institute of Oceanology (Gelendzhik). It was unique experiments in the duration of a person’s stay underwater. The maximum depth for “Chernomor” was identified, the optimal methods of organizing work in underwater inhabited houses and the permissible depths for the use of nitrogen-oxygen breathing mixtures were determined. Specialized medical and physiological research was carried out to develop a methodology for the selection and training of aquanauts for future scientific crews. “Chernomor” was the only underwater house in the world that served on the seabed for five seasons in a row. More than 50 scientists from all over the country worked in it in different crews. The work is a tribute to the memory of all enthusiasts and dreamers: designers and developers, engineers and technicians, divers and scientists, everyone involved in those unforgettable events.