The nodal tide in the Baltic Sea was studied on the basis of the Stockholm tide-gauge readings for 1825–1984; data from the tide gauge at Świnoujście for the same period provided comparative material. The Stockholm readings are highly accurate and are considered representative of sea levels in the whole Baltic; hence, the final computations were performed for the readings from this particular tide gauge for the period 1888–1980. The tidal amplitude obtained from measurements uncorrected for atmospheric pressure or wind field was compared with that forced only by atmospheric effects. The amplitude of the recorded nodal tide was the same as the equilibrium tide amplitude calculated for Stockholm. Calculations for equilibrium tide amplitudes were also performed for the extreme latitudes of the Baltic basin.
The response of semi-realistic wind speed increase scenarios to the mean sea level and current regime of semi-enclosed sub-basins in the Baltic Sea is studied with a 2D hydrodynamic model. According to the model output of spatial mean sea levels, an increase in the westerly wind component by 2 m s−1 leads, for example, to a mean sea level rise of up to 3 cm in windward locations in the study area. The sea level change patterns depend on the wind scenario and coastline configuration. The increases in wind speed considered here also lead to enhanced water exchange through the straits, strengthening of the basin-scale circulation, enhancement of up- and downwelling, and increased bottom stresses near coasts.