Features of water circulation on the Black Sea northwestern shelf based on physical reanalysis results

Abstract

The paper studies the main features of water circulation on the northwestern shelf (NWS) of the Black Sea. The study is based on a physical reanalysis performed previously. The result of reanalysis is a set of hydrodynamic fields for a period of twenty years on a regular grid with a discreteness of one day. To analyze the general properties of the currents on the NWS, the fields were averaged over a monthly period, and further analysis used the monthly average values of them. Spreading of the rivers outflow and wind stress are basic mechanisms, which controls the flow structure in the upper layer of the NWS. Surface currents are directed mainly to the southwest. Along the western coast, a compensatory current is formed, directed to the south, with the exception of the summer months, when the effects of wind are significantly weakened. A characteristic feature of the waters near the western shore is the strong horizontal stratification caused by fresh water with rivers outflow, mainly the Danube. An interesting feature of the circulation on the NWS is presence of a subsurface coastal jet counter-flow directed to the north. The center of this counter-flow is located approximately on the horizon of 20 meters. Its depth may vary, but the counter-flow itself is observed throughout the year.