Decadal variations in mean and extreme sea level values along the Estonian coast of the Baltic Sea

This study presents an overview of the Estonian sea level data set obtained from the coastal tide gauges over the period 1842-2005. Variations in the time-series of annual mean sea level, maxima and minima, as well as standard deviations are investigated and their relationships with variations in the North Atlantic Oscillation index are studied. After correcting the sea level series to spatially varying land uplift rates the series display increasing (1.5-2.7 mm yr(-1)) trends, which in case of Parnu tide gauge evidently exceed the global sea level rise rate. The increase is larger in winter, which is in accordance with similar seasonal structures of the NAO index trends. The rise in mean sea level, standard deviations and particularly in maxima (3.5-11.2 mm yr(-1)) could be explained by the local response to the changing regional wind climate. Due to its windward location the sea level variations in the semi-enclosed study area are sensitive to the ongoing intensification of cyclones and prevailing westwinds. In case of the Parnu Bay, the statistical fit of both the frequency distributions of hourly data and the maximum values distributions for 1923-2005 are inconsistent with the two highest storm surge values of 253 and 275 cm.