The Black Sea Cold Intermediate Layer

Abstract

We focus on the volumetric temperature/salinity analysis of the Cold Intermediate Water (CIW) masses, based on data sets obtained in years with normal, severe and mild winter conditions. A comparative analysis of the 1991 and 1992 data is used to study a convection event during the winter of 1991–1992, and April 1993 and March–April 1995 surveys are used to characterise Cold Intermediate Layer (CIL) peculiarities after severe (1993) and mild (1995) winter conditions. A new analysis of the CIW formation is presented, based on the new data sets having high resolution, full basin coverage. Comparative volumetric T,S analyses do not confirm replenishment of CIW in the peripheral ‘convergence zone’ by water from the cyclonic central region, after being formed there by winter convection, as it had been previously claimed by Ovchinnikov [24]. Subtle evidence supports Kolesnikov’s hypothesis [16] of CIW production over the shelf. Yet, the contribution of this mechanism is found to be small. We find that the formation process is a result of advective and convective contributions most actively taking place along the ‘convergence zone’.