Variability of bottom friction velocity along the inflow water pathway in the Baltic Sea

Abstract Using a regional circulation model of the Baltic Sea with the horizontal resolution of 0.5 nautical miles and with an open western boundary, time series of bottom friction velocity and bottom salinity were simulated for the period of April 2010–July 2016 and analysed at specific points of interest along the inflow water pathway. The model reproduces reasonably well observations of the bottom currents and salinity at monitoring stations in the Bornholm and Gotland deeps. The bottom friction velocity at chemical warfare dumpsites in the Bornholm and Gotland basins was found to be permanently below the resuspension thresholds for the suspended particulate matter and fine sand, and even the Major inflows could not violate the balance. Occasionally the bottom friction velocity may exceed the resuspension threshold for the fine biogenic material (fluffy layer and cysts) almost everywhere in the deep Baltic basins, though additional studies are necessary to assess the likelihood of potential transport and dispersion of the chemical warfare by-products due to high sorption ability of the fine biogenic material.