Sea level variability at the Lithuanian coast of the Baltic Sea

The aim of the paper is to analyse the sea level variability at the Lithuanian coast during the last 100 years using all data available in Lithuania. The analysis, based on sea level data of the Klaipeda Strait for 1898–2002, clearly shows that the long-term sea level increased by about 13.9 cm. Furthermore, it is remarkable that the increase is not found to be linear during the study period. Only a negligible increase is found at every Lithuanian tide gauge until World War II. Starting from the middle of the last century the increase in sea level is more pronounced having a rate of about 3 mm per year since the 1970s. This rise leads to manifold practical problems concerning activities in the coastal areas. The water rise will intensify the intrusion of salty water into the Curonian Lagoon slowly changing the ecosystems in its northern part. The reasons behind this rise are related to enhanced and more frequent advection of warm and moist maritime air masses during the cold season (October–March). This is coupled with intensified air flow from the west with increasing air temperatures followed by rise in water temperatures and thermal expansion of sea water, the global rise of the sea level also playing an important role. The annual mean sea level fluctuation is found to be linked with the winter North Atlantic Oscillation (NAO) index. When the NAO index is positive during winter, the dominating and enhanced westerly flow across the North Atlantic advects relatively warm maritime air over northern Europe. These strong westerly winds cause more frequent flooding events in the southeastern part of the Baltic Sea at the Lithuanian coast.