An Improved Estimate for the Long-Term Mean Sea Level on the Finnish Coast

The main factors affecting the long-term mean sea level on the Finnish coast are the land uplift, the rise of the global mean sea level and the water balance of the Baltic Sea. The sea level variability on a timescale of a year and longer correlates significantly with the North Atlantic Oscillation (NAO) index. Thus, it is possible to express the water balance variability with the aid of the observed or predicted values of the NAO index. This correlation is used to calculate a hindcast for the long-term mean sea level at the Finnish sea level stations. This hindcast follows the observed mean sea levels more closely than the theoretical mean sea level, an estimate used for practical purposes by the Finnish Institute of Marine Research. The possibility to calculate estimates for the future mean sea levels on the Finnish coast is discussed. The differences in the correlation between the NAO index and the mean sea level in different parts of the Baltic Sea are also briefly studied. The mean slope of the Baltic Sea surface is found to correlate with the NAO index.