Temporal variability of the seasonal sea-level cycle in the North Sea and Baltic Sea in relation to climate variability

Based on monthly mean sea-level and meteorological data from the North Sea and Baltic Sea areas, the temporal variability of the annual and semiannual constituents in sea level and meteorological parameters is investigated on decadal time scales. A significant regionally coherent temporal variability of the annual and semiannual constituents in sea level, air pressure, air temperature and the wind field is established. The decadal variability of the annual and semiannual constituents in sea level is found to be closely correlated with the variability in the mechanical atmospheric forcing. This indicates a non-steric contribution to the long-period variations of the seasonal cycle in coastal sea level. In all parameters considered, the largest changes compared to earlier times occurred in the last two decades. The variation found in air pressure indicates an increase of the difference between maritime and continental climate regions in Northern Europe. These variations may be linked to variations of the North Atlantic Oscillation on decadal time scales as well as a general warming trend.