Influence of temperature and precipitation on decadal Baltic Sea level variations in the 20th century

Abstract

It is known that interannual Baltic Sea level variations in the 20th century can be partially, but not totally, explained by the wind forcing linked to the North Atlantic Oscillation (NAO) and other atmospheric circulation patterns. Using regression analysis linking sea level variations (as predictand) and sea level pressure (SLP), precipitation and air temperature (included stepwise as predictors) it is investigated to what extent precipitation and temperature variations can also contribute to explain Baltic sea level variability, in addition to SLP. In wintertime, their additional contribution is small compared to that of SLP (of the order of additional 15% of variance), but it is statistically significant and their inclusion as predictors help to explain past deviations in the evolution of sea level, with higher than normal temperatures and precipitation values linked to a positive contribution to sea level anomalies. In summer, temperature and precipitation explain a substantial part of the sea level variability except in the Kattegat region. In summer positive sea level anomalies are linked to higher than normal rainfall but to lower than normal temperatures, suggesting that the statistical link between sea level and temperature may artificially arise by the observed negative correlation between temperature and rainfall. For some stations, temperature and precipitation can explain, in addition to the variance explained by SLP alone, 35% of the total variability. Since part of influence of temperature and precipitation might be already contained in SLP, this value represents a lower limit for the influence of these additional factors on sea level variability. However, recent trends of winter sea level in the last 20 yr cannot be described by a linear model with any of the predictors used in this study.