FLOW REGIME IN THE IRBE STRAIT

The current structure in a strait connecting a semi-enclosed bay and t he Baltic Sea is studied on the basis of data obtained during the Gulf of Riga Project in 1993-1995. The observations comprised hydrographic snapshots and a 10-day intense campaign IRBEX-95 of CTD, current, sea -level and meteorological measurements. The baroclinic forcing due to the density difference, the barotropic forcing due to the sea-level di fference, and the wind forcing are considered as factors driving the w ater flow through the Irbe Strait. A regular flow scheme (outflow in t he northern part and inflow near the southern slope of the strait) whi ch is related to the quasi-permanent salinity front was shown to preva il on average. Current oscillations having inertial and diurnal period s and forcing-dependent current fluctuations are frequently observed t o be superimposed on the mean structure of the currents. A relatively quick response of the hydrographic fields to almost periodic (2-day) c hanges of the local wind and the sea level is stated. The current is p referably contra-directional to the wind stress, but well correlated w ith the sea level difference between the open sea and the strait. Howe ver, the described regular current scheme seems to contribute the most to the water, salt and nutrient exchange through the Irbe Strait.