Features of Water Circulation in the Northern Black Sea in 2016 and 2017 Based on Numerical Modeling Results with Assimilation of Hydrological Data

Two hydrological surveys carried out in the northern Black Sea in summer 2016 and 2017 are processed with a hydrodynamic model that also assimilates observational data, which made it possible to more accurately describe the meso- and submesoscale features of hydrophysical fields and determine their possible formation mechanisms. High spatial resolution (horizontal grid of ~1.6 × 1.6 km and 27 vertical horizons) and ERA5 atmospheric forcing is used in calculations. The energy terms in the equations of the kinetic and potential energy budget for each year were analyzed to consider possible physical eddy formation mechanisms (baroclinic instability, current flow around coastline irregularities). Such specific features of circulation as the Rim Current along the coast, anticyclonic eddies near the southeastern coast of Crimea, and the area of cyclonic vorticity in the eastern deep-water part of the sea are observed for both years. Along the coast, under the action of weak winds, small-scale eddies were generated when the current was flowing around irregularities in the coastline and bottom topography. A large anticyclonic eddy was formed between 33° and 34° E in 2016 and between 31° and 32° E in 2017. With increased wind action in 2017, more intense currents developed and eddy formations in the upper layer of water were less pronounced than in 2016.