Sea surface temperature variability along the Portuguese coast since 1950

Abstract

Overall an increase in sea surface temperature (SST) has been recorded over the last century. However, changes in SST are not homogeneous across the ocean. Most studies focus on the processes and mechanisms setting SST variability across broad scales and neglect changes occurring at a regional scale. So, this study aims to describe annual, seasonal and monthly time‐series trends in SST along the Portuguese coast, compare trends among areas (Northwest, Southwest and South), quantify SST increase rates and SST time‐series discontinuities. Time‐series analyses showed that SST has the same annual and monthly trend regardless of the area and data sets used (ICOADS: 1950–2010; Satellite data: 1985–2010). SST increased in the three areas: +0.1 °C decade−1 in Northwestern and Southwestern coasts (the same than global average), +0.2 °C decade−1 in the Southern coast. The higher monthly SST increment rates were observed in spring and summer (satellite data: +0.4 °C decade−1 in June in Northwest; +0.4 °C decade−1 in April in Southwest; +0.5 °C decade−1 in June in South). Discontinuities, that is, sudden shifts in time‐series, were observed after 1987, 1995 and 1982–1983 in the Northwest, Southwest and Southern areas, respectively. Overall, this study reinforces the hypothesis that SST varies regionally; so, studies assessing the impacts inherent to climate change along coastal areas, namely fisheries variability, ought to have this perspective into account.