A FRONTAL-RESOLVING MODEL FOR THE GERMAN BIGHT

In this paper the first three-dimensional frontal-resolving model of the salinity front in the German Bight is presented for the simulation of mesoscale frontal circulation in shallow water. The circulation model is a primitive equation model in finite differences which conserves kinetic energy and enstrophy. The density field is computed with dynamically active tracers in a Lagrangian framework. The model is driven by tides, river runoff and wind. First results of the frontal circulation in the German Bight show the development of a density front and a frontal jet parallel to the 30 m depth contour. The advection of the front by tides is well reproduced and the results indicate a tidal dependant convective mixing at the edge of the front. Calculations with different wind forcing show a frontolysis in the German Bight during winds from the southwest except at Amrum Bank where a local frontogenesis occurs. Computations with easterly winds show different transient circulation patterns and-as a new feature-a recirculation cell in the surface layer at the North Friesian coastline. Recirculation might be important in pollution problems because it can cause much longer residence times in the German Bight than those known previously.