Consistency of long sea‐level time series in the northern coast of Spain

Abstract

Sea‐level time series recorded at three stations of the northern Spanish coast (Santander, Coruña, and Vigo) are examined with the aim of obtaining reliable interdecadal trends. The records are about 6 decades long, and their consistency is checked by means of an Empirical Orthogonal Function (EOF) analysis. Major benefits of the analysis are the detection of undocumented changes of sea‐level reference and the filling of data gaps. For the last decade, the consistency of the trends is also checked against shorter, collocated and nearby records. Results indicate that during the second half of the twentieth century, sea level has been rising at a rate of 2.12, 2.51, and 2.91 mm/yr in Santander, Coruña, and Vigo, respectively. Meteorologically induced trends are evaluated from the output of a sea‐level numerical model forced by a re‐analysis of 44 years of atmospheric data. Results are −0.44, −0.27, and −0.21 mm/yr, respectively, indicating that in the study region the meteorological forcing acts in the sense of slightly slowing the sea‐level rise. On the other hand, sea‐level records and the North Atlantic mean temperature exhibit a similar interannual evolution, which points to the thermosteric effect as responsible for the positive trends. Regarding the difference between stations, about a third of it can be attributed to spatial differences in the meteorological forcing. The remaining contribution is attributed to spatial differences in the increase of the ocean heat contents, as suggested by the analysis of SST series during the last decade.