A Model for the Exchange of Water and Salt Between the Baltic and the Skagerrak

Abstract

A model for the exchange of salt and water between the Baltic and the Sea (the Skagerrak) is presented. Because of strong inter-basin interactions in the Baltic entrance area, the model must include the Kattegat and the Belt SEa. These are modeled by horizontally homogeneous two-layer sub-models. The most prominent dynamical properties of the sub-models are wind-driven entrainment flows and rotational-baroclinic, hydraulic controls. The model is driven by a meteorologically forced barotropic transport Qb [calculated from the freshwater supply to the Baltic (Qf) and the sea level fluctuations in the Kattegat], and turbulent entrainment flows coupled to the wind seped W, and in the Belt Sea, also to the barotropic transport. The most important bathymetric features of the basins are included. The model equations are integrated numerically for a test period of 1 1/2 years. The stratification in the Kattegat, as well as in the Belt Sea, is quite well predicted. It is found that approximately one-half of the salt transport into the Baltic is carried out by the dispersive mode associated with the barotropic fluctuations. The effects of (short-term) changes in the external parameters Qh, Qf, W, and S2K (the salinity of the Skagerrak water) upon the stratification in the Belt Sea and the Kattegat are also investigated. Finally, the effects of long-term changes in the external parameters upon the surface salinity of the Baltic are investigated.