Finite element modeling of surface layer circulation in the Caspian Sea

The ocean thermohaline circulation is caused by water density contrasts. This circulation has large capacity of carrying heat around the globe and it thus affects the energy budget and further affects the climate. Henry Stommel's (1958) abyssal circulation article contained the first theoretical analysis of the deep thermohaline circulation (THC). Due to Stommel's reasoning the incoming heat flux via the sun's radiation is stirred downward by wind and the thermal convection, and heats up the waters down to the thermocline and that this subsurface source of heat must be offset by a source of cold if the ocean is not to become continuously warmer. The resulting flow pattern is still used as the zero-order circulation of the deep oceans of the world. Since Caspian Sea is the world's largest inland body of salty water, therefore the study of circulation pattern in this sea for determination of pollution propagation and sediment transport is important. This study is based on a numerical model for prediction of a 2-D behavior of the Caspian Sea circulation due to the effect of uniform surface wind force and density gradients. The model is based on the equations of Navier-Stokes, salinity, and heat applying finite element method. It is assumed that the dominant surface wind is in the north-west direction. Simulation results include flow pattern of the circulation, relative vorticity, and density changes. The subdomain is partitioned into tetrahedral mesh elements and hence, the boundaries are partitioned into tetrahedral boundary elements. The specifications of medium such as fluid velocity under wind stress, inward heat flux, heat capacity of fluid, thermal conductivity, heat, and salinity diffusion coefficients are mentioned. The results of simulation and water circulation show that there are counterclockwise circulations in the South and North Caspian and clockwise circulations in the Middle Caspian. Relative vorticity, circulation and density pattern are presented and at the end some suggestions are made to obtain the results similar to reality.