On pathways and residence time of saltwater plumes in the Arkona Sea

Time series measurements of temperature, salinity, and current at the sills of the Arkona Basin have been performed during the winter seasons 1998/1999 and 1999/2000 together with ship‐based measurements of stratification and currents covering the whole Arkona Basin. Observations were supported by model simulations of saltwater inflow into the Arkona Basin. The pathway of the saltwater plume passing the Drogden Sill stretches southward along the western rim of the Arkona Basin and turns into the deeper parts of the basin through a trench at the northern rim of Kriegers Flak discharging at the eastern tip of Kriegers Flak into the saltwater pool in the center of the Arkona Basin. The saltwater plume branches into a western filament, which passes the gap between Mön Island and Kriegers Flak if its mass flux exceeds the transport capacity of the trench. The western filament drops down to the bottom of the SW Arkona Basin, which causes mixing and eddy shedding. The salt water passing the Darss Sill flows onto a wedge‐shaped submarine terrace stretching from the Darss Sill to Kap Arkona. This plume joins near Kap Arkona by dropping into the underlying western Drogden Sill plume associated with mixing and eddy shedding. The central saltwater pool of the Arkona Basin discharges geostrophically controlled through the Bornholm Gatt into the Bornholm Basin. An upper bound of the discharge time of the saltwater pool based on repeated temperature‐salinity diagrams was estimated to be 3 months, while the residence time estimated by an analytical model was 1 month. Mixing of the saltwater pool with the overlying brackish surface water was observed.