Long-Term Tendencies in the Variability of Characteristics of the Black Sea Pycnocline

摘要

The rise of the waters of the main pycnocline in the central part of the western cyclonic gyre at the end of the winter in the 1960s-1970s and their deepening in the eastern cyclonic gyre from the mid-1960s to the late 1980s were revealed on the basis of archival hydrologic data obtained on the standard sections of the Black Sea in 1957-1992.It is shown that,simultaneously,the waters of the pycnocline descended in the Seva-stopol anticyclone and rose in the Yalta and Batumi anticyclones.These tendencies indicate that the water cir-culation intensified in the region of the western cyclonic gyre(off the southwestern coast of the Crimea)and weakened in the vicinity of the eastern cyclonic gyre at the end of the winter season in the 1960s-1970s and in the 1960s-1980s,respectively.It is shown on the basis of NCEP reanalysis data and archival hydrometeorolog-ical data that all major circulation factors,such as a decrease in the cyclonic vorticity in the wind field during the winter season,changes in its spatial structure,an increase in the river discharge,and a decrease in the tur-bulent heat fluxes at the Black Sea surface,affect the energy redistribution between the gyres.The role of each of these factors is analyzed.