Evolution of mixed layers in a stratified region of the Black Sea anticyclonic eddy

A detailed analysis of hydrology, hydrodynamics, and microstructure of an anticyclonic eddy is performed. We use the field data obtained in May 2004 at the shelf edge in the northwestern part of the Black Sea. We study the spatial distributions of the Brunt-Väisäl number, and regions of mixing with a vertical scale on the order of 2 m. Possible mechanisms of generation and maintenance of the observed mixed layers are analyzed. A conclusion is made that the investigated eddy in the northwestern part of the Black Sea (possibly similar to the other natural eddies in the northwestern part of the Black Sea) is able to modify the fine layered structure of the scalar hydrophysical fields in the upper 150-m layer forming and maintaining the layers of low vertical gradients with vertical scales of ∼2 m and up to 50–100 km in the horizontal direction owing to the local shear instability of the horizontal flow.