On the dynamics of the large-scale circulation of the Skagerrak

Characteristic features of the large-scale hydrography of the Skagerrak are reviewed. A dominant overall feature is the deep reaching cyclonic circulation. The modelling of the circulation in the Skagerrak, as part of the current pattern in the North Sea is discussed. Simplified mechanistic models are derived to elucidate the governing dynamics. Qualitative and quantitative implications of these models are compared to what is known from observations. It is concluded that the basic cyclonic circulation in the area is to a large extent forced by the mixing of high-saline deep water into the outflowing low-saline surface water of Baltic origin. The time-dependent part of the motion, on the other hand, is probably an effect of the local wind as well as of the wind over the rest of the North Sea. In both cases the topography, viz. the existence of the Norwegian Trench, plays a crucial role.