Abstract:
The physical behavior of the Mediterranean flow entering the Black Sea through the Bosphorus Strait is described using a variety of high-frequency acoustic systems. Because of the density difference between salty Mediterranean and fresh Black Sea water, a two-layer exchange is formed which is confined within a canyon in the Black Sea exit region of the Bosphorus Strait. A 307-kHz acoustical scintillation system placed 6 m from the seafloor and covering a 300-m propagation path is used to describe the mean Mediterranean current speed and the turbulent velocity fluctuations within the bottom boundary layer of the Mediterranean flow during a 4-day period when the exchange was maximal. In the idealized case of isotropic and homogenous turbulence, estimates of the turbulent kinetic energy dissipation rate leads to values ranging from 1x10[sup -6] to 5x10[sup -5] W/kg[sup -1]. A 600-kHz broadband acoustic Doppler current profiler placed within the canyon shows that the two-layer exchange displays temporal variability over scales of a few days associated with the meteorological conditions in the Black Sea. To help interpret the oceanographic measurements, a 120-kHz high-resolution echo sounder is used to obtain two-dimensional images of the two-layer exchange.