Some comments on the barotropic flow through the Danish Straits and the division of the flow between the Belt Sea and the Öresund

Abstract

The flow between the Baltic Sea and the Kattegat takes two routes, the Belt Sea and the Öresund. The division of the flow between the Belt Sea and the Öresund is discussed. The currently widely used estimate is based on results from a model for the barotropic flow through the Öresund and current measurements in the Belt Sea. By using a recently established, thoroughly calibrated model for the barotropic flow in the Öresund and existing models for the total flow through the Danish Straits, it is found that the mean division of the instantaneous flows through the Öresund and the Belt Sea is 2 : 8, rather than the at present generally accepted estimate 3 : 8. The division of the net outflow from the Baltic is an unsolved problem, due to the difficulty to determine the net flow separately in the straits. By using the models and some qualitative arguments it appears that the division of the net outflow may be approximately 1 : 1. Some comments on and results related to the difficulty to determine the net flow from current measurements or models of the barotropic flow are also given.