Coastal up - and downwelling in the southern Baltic *

A three-dimensional hydrodynamic model was used to determine 12 zones of upand downwelling in the southern part of the Baltic Sea. On the basis of a seven-year numerical simulation, the annual frequency of upand downwelling events in various regions was analysed, their vertical velocity evaluated and the probability of their occurrence for different wind directions calculated. Verification of the model results demonstrated their good correspondence with satellite images, on average equal to 92%. The poorest consistency was recorded for upwelling in the Bornholm region (81%). The annual average frequency of strong upwelling (velocities > 10−4 m s−1) ranged from c. 5–7% off the eastern coasts of the southern Baltic to > 31% along the north-eastern coast of Bornholm. Along the Polish coast (excepting the Vistula Spit) downwelling was recorded more frequently than upwelling. The frequency of strong vertical currents was highest in the area to the north of the Hel Peninsula, where high percentages of strong upwelling (27.1%) and downwelling (37.1%) were recorded. * This research was supported by the State Committee for Scientific Research, Poland (grant No 6 P04G 061 17). Editing assistance of the article was provided by BALTDER (EVK3-CT-2002-80005), funded by the European Commission under the 5th Framework Programme. The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 454 M. Kowalewski, M. Ostrowski