Modelling the gravity current flowing from the Bosphorus to the Black Sea

摘要

We present here results of numerical simulations with a non-hydrostatic 2-D radial model of the Mediterranean Sea dense plume with saline and warm water intruding the less dense Black Sea. The model takes into account the typical vertical temperature and salinity distribution for the summer season and the peculiarity of the bottom relief in the pre-Bosphorus Strait area. The horizontal density gradient occurring near the bottom at the depth 50-75 m is used as external forcing. The motion in the system starts from a state of rest. The gravity current with Mediterranean Sea Water moves down the shelf-slope and mixes with Black Sea Water, separates from the slope when its buoyancy becomes neutral and extends further in the horizontal direction as an intrusion. The depth of the current detachment depends on the salinity and temperature values of the inflowing Mediterranean Sea Water. Having the same density as the ambient water, the lens can be detected by the value of the temperature which can be lower or higher than that in the Black Sea. The gravity current is partly mixed with the Cold Intermediate Layer (CIL) of the Black Sea, which itself has a temperature of less than 8degreesC, and its core is placed at a depth of 50 m. The intermediate case when the intrusion has the same temperature as the Black Sea Water is also possible; then the lens can be detected only by the value of light transmission or concentration of the same chemical elements (e.g. phosphate or sulphide). The horizon of the lens separation from the slope also depends on the intensity of the mixing processes which accompany the propagation of the gravity current across the shelf-slope. The presence of the lenses with cold water is confirmed by in situ measurements. [References: 27]