The forcing of mean sea level variability around Europe

Mean sea level variability around the European coasts is explored on the basis of regional sea level indices derived through Empirical Orthogonal Function Analysis (EOF) of tide-gauge records. The regional indices are cross-correlated amongst themselves and against the major regional and climatic indices. The analysis is done for the whole year as well as seasonally. The effect of coherent atmospheric pressure signals is explored by comparing the results of the analysis before and after the data are corrected for the atmospheric pressure effects. The North Atlantic Oscillation Index (NAO) and the Mediterranean Oscillation Index are the major regional indices which are found to be significantly correlated with sea level variability around Europe. Their correlation is positive for the Northern European coast and negative for the Mediterranean coasts. The NAO influence causes an anticorrelation between northern and southern European sea level. This is stronger in winter and weakens significantly or disappears completely during the summer. When the NAO influence was removed from the regional mean sea level indices the cross-correlation between the various regions was reduced. However, residual spatial coherency indicated that probably there are other mechanisms causing spatial coherency. No statistically significant correlation with the Southern Oscillation Index (SOI) was found.