Projection of physical conditions in the North Sea for the 21st century

A global climate scenario run based on the IPCC future emission scenario SRES was dynamically downscaled for the North Sea, using an uncoupled meso-scale model system. The atmospheric forcing shows an increase in air temperature during the 21st century with stronger warming in whiter than in summer. These trends are reflected by an increase in annual mean sea surface temperature of similar to 1.8 degrees C. The strong warming in winter is the main driver for the total warming of the North Sea, as indicated by the analysis of surface heat flux components. The thermocline weakens in intensity according to the changing temperature profiles, and its mean depth slightly decreases due to lower wind speeds. The salinity in the North Sea drops by similar to 0.6 psu because of decreasing salinity of the inflowing Atlantic waters, increasing Baltic discharge, and higher downward surface fresh water fluxes. Some of our results disagree with other dynamical downscaling studies, as the results depend on the parent global model. In general, the downscaled projected trends qualitatively agree with the results of the coarser global model. Nevertheless, in particular, the magnitudes of the surface heat fluxes, the formation of the frontal system, and the strength and structure of the general circulation are more realistically represented in the regional meso-scale model.