Interannual variability of Danube waters propagation in summer period of 1992-2015 and its influence on the Black Sea ecosystem

During the years with prevailing southeastern winds (~ 40%), the Rim Current is less intense. Mesoscale eddies effectively trap the Danube waters, transporting them to the deep western part of the basin. The low- and high-frequency southeastern wind-drift currents contribute significantly to cross-isobath plume transport and its connection with offshore circulation. During several years (~ 15%), the Danube waters moved eastward to the west coast of Crimea. They were transported on the north periphery of the mesoscale anticyclones due to prevailing eastward wind-drift currents. During the years with hot summers, a monsoon effect induced the formation of a strong anticyclonic wind cell over the NorthWestern Shelf (NWS), and the plume moved northward (~ 15%). Anticyclonic wind circulation leads to the Ekman convergence of brackish surface waters in the centre of the shelf and the formation of a baroclinic geostrophic anticyclone north of the NWS. This anticyclone traps the Danube waters and forces them to remain on the shelf for a long period of time. The impact of the propagation of the plume on the variability in chlorophyll a chlorophyll a in the NWS and the western Black Sea is analysed in this study based on satellite data.