Abstract
Abstract. Coastal sea-level trends in the Baltic Sea display decadal-scale variations around a long-term centennial trend. In this study, we analyse the spatial and temporal characteristics of the decadal trend variations and investigate the links between coastal sea-level trends and atmospheric forcing on a decadal timescale. For this analysis, we use monthly means of sea-level and climatic data sets. The sea-level data set is composed of long tide gauge records and gridded sea surface height (SSH) reconstructions. Climatic data sets are composed of sea-level pressure, air temperature, precipitation, evaporation, and climatic variability indices. The analysis indicates that atmospheric forcing is a driving factor of decadal sea-level trends. However, its effect is geographically heterogeneous. This impact is large in the northern and eastern regions of the Baltic Sea. In the southern Baltic Sea area, the impacts of atmospheric circulation on decadal sea-level trends are smaller. To identify the influence of the large-scale factors other than the effect of atmospheric circulation in the same season on Baltic Sea sea-level trends, we filter out the direct signature of atmospheric circulation for each season separately on the Baltic Sea level through a multivariate linear regression model and analyse the residuals of this regression model. These residuals hint at a common underlying factor that coherently drives the decadal sea-level trends in the whole Baltic Sea. We found that this underlying effect is partly a consequence of decadal precipitation trends in the Baltic Sea basin in the previous season. The investigation of the relation between the AMO index and sea-level trends implies that this detected underlying factor is not connected to oceanic forcing driven from the North Atlantic region.
Highlights
The global mean sea-level trend has risen over the 20th century at an approximate rate of 1.7 mm yr−1, with higher rates of about 3.2 mm yr−1 as measured by satellite altimetry over the past 30 years (Church and White, 2011; Nerem et al, 2010)
To confirm that this link is valid for the decadal trends, we show in Fig. 3 the correlation pattern between the decadal trend of the North Atlantic Oscillation (NAO) index and the decadal trends of 29 tide gauges in the Baltic Sea in wintertime
The stations along the southern part of the Baltic Sea have a weak link to the NAO, and the effect of the NAO becomes stronger towards the north of the Baltic Sea
Summary
The global mean sea-level trend has risen over the 20th century at an approximate rate of 1.7 mm yr−1, with higher rates of about 3.2 mm yr−1 as measured by satellite altimetry over the past 30 years (Church and White, 2011; Nerem et al, 2010) This rise is projected to continue at high rates in the future due to global warming. In the tropical western Pacific, these trends may attain a value of 15 mm yr−1, whereas in the mid-latitude eastern Pacific the trends are negative, of the order of −5 mm yr−1 These regional differences in observed regional sea-level trends are likely caused by spatially heterogeneous atmospheric forcing and ocean internal variability
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