Climate change induced decadal variations in hydrodynamic conditions in the Eastern Baltic Sea

Climate change manifests in the Baltic Sea region as increasing air and water temperatures, decrease in salinity and in shortening of the ice period. In addition, atmospheric westflow and storminess has intensified, which should also lead to changes in hydrodynamic regime of the sea. The objective of the paper is to study these changes in the practically tideless, fetch-limited nearshore region of West Estonia. The study is based on meteorological and sea level data from the Estonian weather and tide gauge stations, as well as on hydrodynamic modelling experiments with the shallow sea 2D model and wave hindcast for the period 1966-2008. Corrected with locally varying postglacial land uplift rates, the sea level rise according to the Estonian data was 1.5-2.7 mm/year over the period 1842-2009. Steeper than the lobal sea level rise, the rise in winter sea level, and particularly in annual maxima (3.5-11.2 mm/year), could be explained by the local sea level response to the changing regional wind climate. There are site-dependent changes in current patterns and upwelling occurrences. The significant wave heights exhibited some quasiperiodic cycles with the last high stage in 1980-95 and a slightly decreasing overall trend. As a result of northward shifts in cyclone trajectories, annual maximum waves have increased along the windward coasts of West Estonia, but decreased on the northern coast.