In this coordinator report from the QuantAS-Off project funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) preliminary results are summarised. First, the sensitivity and ecological role of the water exchange between the North Sea and the Baltic Sea is discussed. Results for the natural variability and mixing are presented, derived from detailed field and model studies carried out within QuantAS-Off and another project within the QuantAS project cluster. It is shown that the dynamics of Baltic Sea inflow events is far more complex and variable than assumed before. Major focus is set on the quantification of the impact of structures such as cylinders (from wind turbine foundations) on the inflowing dense water masses. These studies are based on laboratory measurements (University of Rostock), local numerical simulations (University of Hannover) and field observations near obstacles in the Baltic Sea (Baltic Sea Research Institute). Then, a parameterisation of structure mixing for large scale regional hydrostatic ocean models is suggested, based on a quadratic friction law. Strategies for calibration are discussed. Finally, mainly based on the local simulations by the University of Hannover, a first quantification of mixing due to wind farms is attempted. The result is that wind farms, depending on their location, may have a dynamic influence on the exchange between the North Sea and the Baltic Sea, but that the uncertainties are still too large to give definitive estimates. During the last phase of the QuantAS-Off project, the three project partners will further cooperate to improve the predictability for structure induced mixing. This work will mainly be based on improving the structure friction parameterisation by calibrating it against the laboratory simulations and local numerical simulations and then carrying out regional model simulations for the Western Baltic Sea with this parameterisation implemented, considering a variety of wind farm distributions.