The general tendencies of long-term changes of the Black Sea density structure in the 20-th century are revealed on the basis of oceanographic data re-analyzis. Low-frequency variability of vertical stratification, horizontal density gradients and geostrophic circulation intensity is considered. External forcings exerted on the density structure and its significance are discussed.
Based on satellite data for the period 2005 – 2011 the following characteristics of vortices generated over the continental slope in the north-western and western parts of Black Sea were analyzed. A number of vortices generated by the term of their existence and intensive development were calculated. The front position and direction of water transfers in the most typical eddies were determined. Close relationship of eddy activity in the area that is foreseen with thermal state in winter and variability flow of the Danube.
The nature of the formation of the Black Sea surfaces circulation is examined on the hydrological surveys in the spring (April), summer (July), autumn (September) and winter (February-March) seasons. The main role of the river freshet in the formation of the Black Sea surfaces circulation and the consecutive seasonal development of its intensity at the first – the western gyre (April), and then – the eastern gyre (September) is shown as by the climatic and the specific hydrological surveys.
On the basis of adaptative computations in the framework of three-dimensional numerical model with high spatial resolution and data of reanalysis relationship between the interannual-decennial changeability of largescale circulation in the Black sea and the vorticity of wind field is examined. Two types of adaptative computations for October-November and February-March are analyzed. First series of numerical experiments are carried out on the basis of adaptation of the archival temperature and salinity data for 30 years and wind fields averaged for ten-year periods. The second series of computations is conducted from the data joined in groups for years with the high and low values of the vorticity of wind field. It is shown, that for interannual scale the intensity of large-scale circulation in the Black sea is connected with changeability of middle vorticity of wind fields over the sea. For ten-year scale such relationship is not revealed. Though increasing area with prevailing cyclonic vorticity of wind fields for ten year scale is accompanied by strengthening of middle flows.
The intensity and direction of the marine water transport at the boundary of the north-western Black Sea shelf on the sections between the stations Primorskoe – Zmiinyi Island – Chernomorskoe using of the sea level data on these stations was evaluated. The conclusion about the periodic formation in 2005-2006 of the coastal anticyclonic gyre close to Zmiinyi Island was based: transport from north to south in the periods April – July 2005 and May – December 2006 but transport of the sea water masses from south to north in the period August 2005 – April 2006. The method of the restoration the missing sea level data was testing and results was very positive.
It is considered a spatial position, seasonal variability and intensity of the main flow and cyclonic circulation of the Black Sea waters along the axis of divergence, identified and selected according to the results of dynamical calculations of the climatic data set of temperature and salinity in surface and intermediate layers of the Black Sea. The important role of spring floods on the rivers of the NWBS in the development of the water circulation features was shown because of this river’s water and MBSC interaction with the periphery of the western and eastern cyclonic circulation. This process causes domination at the western part sea surface cyclone – in spring and at eastern – in summer and autumn. The flow rate and nature of seasonal migration cyclonic centers were estimated.
The presence of the second (winter) maximum at an annual distribution (40-60 % of cases) as volumes of the river’s waters (Danube and Dnepr) so the Black sea level at stations of northwest coast is shown. The general tendency of the growth of a sea level on mid-annual and mid-winter data is marked in interannual variability which is not connected with increase the volumes of the river’s waters. The sea level in the Odessa region depends on Danube waters (r=0.8-0.9) but on Dnepr waters (r≅0.5) connection is present with the nearest stations – Ochakov, Odessa and Ilyichevsk. The differences in character of fluctuations of volumes of the Dnepr waters to other considered parameters are observed.