Tidal Gauge Data in Deducing Secular Trends of Relative Sea Level and Crustal Movements in Portugal

Abstract

Along the Portuguese coast there are four tide-gauge data series that exceed 10 years. However, only those of Cascais and Lagos can be considered reliable indicators of long-term changes in relative sea level. A rise in relative sea level of 1.3 ± 0.1 mm/year and 1.5 ± 0.2 mm/year, respectively, can be found. The comparison of Cascais data with the evolution of sea surface temperature of North Atlantic Ocean suggests that thermal expansion of ocean is responsible for a large part of the observed rise. The reversal in the Cascais long-term trend detected around 1920 might be connected with the end of the "Little Ice Age". The determination of land elevation changes using Cascais and Lagos data was tried. The results point to a possible relative uplift of the Lagos station at a mean rate of 0.3 ± 0.2 mm/year.