40 years of changes in sea surface temperature along the Western Iberian Coast

Climate change is causing mean sea surface temperatures (SST) to increase worldwide. However, this increase has not been temporally or spatially uniform, with variations observed depending both on the period considered and the geo-graphic region. In this context, this paper aims to quantify relevant changes in SST along the Western Iberian Coast over the last four decades, through the calculation of trends and anomalies of long-term time series of in situ observa-tions and satellite-derived data. Potential drivers of SST changes were considered using atmospheric and teleconnections time series. Changes in the seasonal cycle of SST were also evaluated. We show that SST has increased since 1982, with regional variations between 0.10 and 0.25 & DEG;C per decade, with an increase in air temperature appearing to drive the SST trends along the Iberian coast. In the near-shore area, no signif-icant trends or changes in the seasonal cycle of SST were observed, which is likely due to a buffer effect caused by the seasonal upwelling that characterizes the region. Recent decades show a slowdown in the increase rate of SST along the Western Iberian Coast. An upwelling intensification could justify this observation, along with the effect of teleconnections on the regional climate, such as the North Atlantic Oscillation (NAO) and the Western Mediterranean Oscillation Index (WeMOI). Our results suggest that the WeMOI plays a more important role in coastal SST variability than the other teleconnections.

Automated summary

Climate change is causing spatially and temporally non-uniform increases in mean sea surface temperatures (SST) worldwide. This study aims to quantify changes in SST along the Western Iberian Coast over the past four decades by analyzing long-term time series data. The results show regional variations in SST trends, with an increase in air temperature appearing to be the main driver. The seasonal cycle of SST and trends in near-shore areas were not significantly affected, likely due to the buffering effect of seasonal upwelling. Recent decades have shown a slowdown in SST increase, potentially due to upwelling intensification and the impact of teleconnections like the North Atlantic Oscillation and the Western Mediterranean Oscillation Index.