Physical oceanography variability Zn the Black Sea pycnocline

Local variability of the Black Sea permanent pycnocline position is caused, basically, by dynamical processes: Ekman pumping, meandering of the Rim current, mesoscale eddies, etc. Recent CTD measurements allow to filter local effects and to study variations of the pycnocline structure in detail with the focus on understanding of the role of different mechanisms which cause these variations. Gradual deepening of the isopycnal interfaces since 1991 as well as cooling (freshening) tendency has been registered. The total range of migration of the sigma-t interfaces within the pycnocline was 9 - 11 meters, with the shallowest position in 1990-91 and the deepest position in 1994. In the particular case, both cooling and freshening during 1991 - 1994 period, to some extent, occurred in response to changing vertical velocity. Cooling in this sense may not coincide with respective variation of annual mean air temperatures. In speculative manner, there should be a balance between combined variations of the basin's water balance, winter meteorological conditions and the thermohaline structure of the pycnocline layer. Weather conditions for the warm part of the year complicate the response in the pycnocline