Decadal Variability of Characteristics of the Black Sea Pycnocline and Geostrophic Circulation in the Wintertime

A. B. Polonskii and I. G. Shokurova

The Black Sea density fields and geostrophic circulation in the 0–300-dbar layer are reconstructed from the February archive hydrological data for several decades from 1951 to 1995 and then their interdecadal variability is studied. A gradual rise of the pycnocline is noted in the dome region of large-scale cyclonic gyrals from 5 m at the top of the pycnocline to 10–15 m at 100–300-m levels. Differently directed tendencies of long-term variability of the winter circulation are revealed: circulation intensification in the upper 0–50-m layer (except for the southwestern sea) and weakening in the lower pycnocline 200–300-m layer. The connection with the wind vorticity variability, river runoff, precipitation, and air temperature is analyzed. Strengthening of the cyclonic wind vorticity in the 1960s and the early 1970s is in good agreement with the circulation intensification of that time in the eastern sea.