Abstract
Only recently, medium intensity inflow events into the Baltic Sea have gained more awareness because of their potential to ventilate intermediate layers in the Southern Baltic Sea Basins. With the present research activities within the BMU project QuantAS-Off (Quantification of water mass transformations in the Arkona Sea – Impact of Offshore Wind Farms) a first attempt is made to obtain estimates of turbulent mixing in this area where dense bottom currents resulting from medium intensity inflow events are weakened by turbulent entrainment. With the help of cruise- and station-measurements, numerical localand regional-scale modelling and lab modelling, scientists from the Baltic Sea Research Institute, the University of Rostock and the University of Hanover are bringing their knowledge and techniques together to obtain an estimate of additional turbulent mixing of Offshore wind Farms to dense bottom currents. This estimate is then being implemented into a high-resolution regional model running at the Baltic Sea Research Institute of Warnemünde. This numerical model simulation, which is carried out using the General Estuarine Transport Model (GETM; www.getm.eu) during nine months in 2003 and 2004, has already successfully been validated by means of three automatic stations at the Drogden and Darss Sills and in the Arkona Sea with an agreement that is fairly good representing the strength and occurrence of inflow events. A bulk measure for mixing activity is then introduced, the vertically integrated decay of salinity variance, which is equal to the production of micro-scale salinity variance. This measure identifies the Drogden and Darss Sills as well as the Bornholm Channel as mixing hot spots. Further regions of strong mixing are the dense bottom current pathways from these sills into the Arkona Sea, areas around Kriegers Flak (a shoal in the western Arkona Sea) and northwest of the island of Rügen.