A possible ventilation mechanism of the aerobic zone in the Black Sea may exist, caused by a descent of oxygen-containing water down the bottom slope in the Ekman boundary layer. To study this theory three long-term (1.5-2 months) installations of automatic bottom stations were carried out in 2018-2019 on the Black Sea shelf/continental slope in the depth range from 80 to 243 m. The stations were placed on a coastal cross section on the beam of the Tolstyi Cape (the Gelendzhik Bay). They recorded the hydrophysical (temperature and salinity of water, pressure and flow rate) and hydrochemical (dissolved oxygen concentration) parameters at 0.5-2.5 m from the bottom. The acquired data were used to estimate the spatiotemporal scales of water transfer in the bottom layer along the slope. Our analysis had confirmed the existence of the bottom water transport normal to the shore. A downward flow was observed in the case of an intensive north-western alongshore current. This type of water movement corresponds to both the geostrophic adjustment and the dynamics of the bottom Ekman boundary layer. However, changes in water density in the bottom layer, which occur due to the water movement up and down the slope, were of the same range as those observed in the water column at the same depth. This fact casts doubt on the efficiency of the Ekman transport in the bottom layer as the ventilation mechanism for water of the upper continental slope of the Black Sea.
Black Sea, shelf-slope zone, northwestern current, bottom boundary layer, downward Ekmantransport, water oxygen ventilation
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