Coupled Hydrodynamic Ecosystem Model of the Black Sea at Basin Scale

Abstract

A hydrodynamical model of the general circulation in the Black Sea has been build up, using the GHER primitive equation model. In a first experiment, a model with 15 km horizontal resolution and 20 vertical levels is used to compute the typical seasonal cycle by forcing the model with climatological monthly mean fields of temperature, salinity and wind stress at the air sea interface. Furthermore, the corresponding river discharges of the Danube, Dnestr, Dnepr and Rioni are taken into account. The simulation results are presented in view of their later use in a 3D ecosystem model. An ecosystem model at basin scale is then defined by a nitrogen cycle, which is described by 5 state variables, i.e. NO 3 − , NH 4 + , Phytoplankton, Zooplankton and Dissolved organic matter. This model has been chosen as a first test for coupling the 3D hydrodynamical model and the ecosystem model. The ecosystem model is imbedded on-line into the 3D hydrodynamical model with a superimposed cycle for the light intensity. In this paper, the main findings of the hydrodynamic model are summarized stressing those aspects of the current and hydrological fields that affect the ecosystem. The ecosystem model is briefly described emphasizing the modifications made to adapt the equations to the Black Sea’s environmental conditions.