INTERACTIONS OF WIND AND DENSITY DRIVEN CURRENTS IN NORTH-SEA ROFIS -A MODEL STUDY

\Three different versions of a baroclinic three-dimensional circulatio n model of the North Sea are used to obtain information on the wind an d density interactions in the North Sea ROFIs (Regions Of Freshwater I nfluence): the standard version with fully prognostic treatment of sal inity and temperature is compared to a barotropic model run on the sam e grid on the one hand and to an also fully prognostic model run on a four times coarser grid on the other hand. In order to gain knowledge on the wind and density interactions, two opposing wind directions are chosen for investigation, namely a time of strong north wind, 21st-28 th April 1982, and a time of strong southwest wind, 22nd-24th May 1982 . In the April case the effect of the salinity gradients on the border of the ROFIs of Rhine, Weser, Ems and Elbe, i.e. along the continenta l shore, is shown to lead to a clear enhancement of the mean surface c urrents. In May this result is partly disguised by the additional effe ct of the thermocline in the deeper parts of the North Sea, i.e. in th e classical shelf sea regime region. Nevertheless, the same pattern of enhanced mean surface currents along the coast is detected and is of the same order of magnitude as in the April case. It is thus concluded that although the circulation in the North Sea is reversed by the win d, the density induced component of the general circulation is modifie d only slightly. (C) 1997 Elsevier Science B.V.