The role of lateral fluxes in ventilation of the Black Sea

This paper describes a stationary one-dimensional model of vertical exchange in the Black Sea. The model, formulated within the framework of the inverse problem, is based on the balance of heat, mass of salt and mass of water for the entire basin. The source of salt is the Bosphorus effluent. It is assumed that the process of transformation of the inflow goes in three phases. (i) In the upper layer, the ambient fluid is entrained to the inflow and a plume is formed. (ii) A breakdown of the plume and the formation of isopycnal intrusions and penetration of the plume water into the ambient fluid occur below a certain depth. This depth is found from the analysis of the T, S data. (iii) A part of the plume flows down into the bottom homogeneous layer. The latter phase is important to compensate for the loss of salt from this layer. The influence of the plume on the interior is realised in the form of a source-function distributed over the vertical. The solution describes vertical distributions of eddy diffusivity and vertical velocity in the interior domain of the basin. It is shown that the total upward heat flux from the pycnocline notably exceeds the value of the geothermal heat flux revealing the dependence of thermal conditions in the water column on thermal properties of the plume. The geothermal heat controls thermal regime below the pycnocline, where the plume is a cold water pattern compared with ambient water. The result explains the existence of an intermediate quasi-isothermal layer observed from 500 to 650 m.