Mediterranean Water in the Strait of Istanbul (Bosphorus) and the Black Sea Exit

Abstract

Mediterranean water is always present in the Strait of Istanbul (Bosphorus) and it extends as a salt wedge into the Black Sea. Approximate average slopes of the surface (Black Sea) and bottom (Mediterranean) waters were determined along the Strait. Asymmetry observed in the interface slopes reflects the influence of hydraulic controls along the Strait and in the Black Sea exit. Bottom layer slopes are 1·6 and 1·4 m km −1in the southern part and 0·5 m km −1in the northern part. Results of the first moored current measurements and variability of the bottom-water salinity in the northern sill are given. Bathymetry and morphology of the sea-bed channel extension into the Black Sea, confinement of the Mediterranean water into the channel, and its slope were studied using recent hydrographic and seismic surveys. Based upon recent data on channel geometry and current measurements at the northern sill, Mediterranean water inflow was estimated to be 101·0 km 3year −1. Current and salinity measurements in the northern sill indicated short (∼15·0 h) and long (e.g. 10·6 days) period oscillations. Under the control of topography, Mediterranean water extends for about 7·5 km into the Black Sea with a slope of approximately 2·0 m km −1. It first runs northward and subsequently spreads westwards. The approximate spreading area of the Mediterranean water in the Black Sea far-field region was determined.