Climate-sensitivity of European marginal seas, derived from the interpretation of modelling studies

This investigation starts from our general knowledge about the regional oceanography of European seas and makes some first guesses on their climate sensitivity, based on the results of regional models. For the modelling of convection in the water column and on the continental slope new, process-oriented models were applied. The watermass properties of the seas investigated are largely governed by the mixing of Atlantic water and continental freshwater. Two marginal seas in mid latitudes, the North Sea and Baltic, and the largest European shelf sea in high latitudes, the Barents Sea, are discussed. In the mid latitude seas the relationships between circulation, mean sea level, haline stratification and heat budget are compared and their climate sensitivity estimated. We expect that in particular the Baltic will be susceptible to a climate change because of a strong feedback between sea surface and air temperatures with the haline stratification. The investigation of the convective watermass formation on a shelf at high latitudes suggests that the export of dense shelf bottom water into the adjacent ocean is particularly sensitive to the supply of freshwater. Atlantic heat imported to the shelf provides a negative feedback to the convection and may prevent formation of dense bottom water. The role of the slope-convection in forming deep watermasses is similar in the Arctic Ocean and the Mediterranean Sea: in both cases it accounts for a net downward transport of heat and salt.