Interannual to decadal sea level change in south-western Europe from satellite altimetry and in-situ measurements

Abstract

Interannual to decadal sea level changes are investigated in the Iberian Peninsula in the interval 1993-2001 using satellite altimetry and tide gauge measurements. Eleven locations, six in the Mediterranean Sea and five in the Atlantic Ocean, are selected. Monthly de-seasoned sea level values are low-pass filtered to focus on signals with periods longer than one year. The correlation of altimetry and tide gauge monthly values is higher than 0.7 and significant at the 95% level at many of the locations, is regionally dependent and increases when using low-pass filtered data. The long-term components of the sea level height differences are mostly smaller than +/- 3 mm/yr. The sea level is inversely correlated to the North Atlantic Oscillation climatic index and the correlation increases at interannual time scales. A relative maximum in sea level in the years 1996-1997 coincides with a relative minimum of the North Atlantic Oscillation index. A maximum in the same time interval is observed in steric heights computed from hydrographic databases, that correspond to the change in sea level due to volume change. The correlation between steric heights and tide gauge yearly values in 1993-1998 is regionally dependent and significant at the 90% level at a few locations in the Mediterranean Sea. Highest values are reached with steric and thermo-steric heights of Medar/Medatlas in Malaga (0.7) and with thermosteric heights of World Ocean Atlas 1998 in Ceuta and Algeciras (0.8).