Red Sea warming and its links to the Red Sea dipole and upwelling mechanisms

Abstract

A comprehensive analysis of changes in sea surface temperature (SST) was performed across the Red Sea for the period 2003 to 2020 using satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua. Employing a regionalization scheme based on principal component analysis (PCA), five homogenous sub-regions were identified that explain about 85 % of the total variation in SST across the Red Sea. The results indicate that there is a diverse and complex range of SST variability throughout the Red Sea. Spatially, distinct SST trends were observed between the southern (PC1) and northern (PC3) regions, which show northward enhancement in the rate of SST trends. A zonal contrast in the rate of warming over the western and eastern sectors was also observed, exhibiting more pronounced warming trends along the western coasts. In contrast to the offshore and deep waters, surface warming in shallow waters (depth < 100 m) was more pronounced, which poses detrimental effects (e.g., thermal coral bleaching) on regional marine ecosystems. We found a robust link between spatial patterns of SST anomalies and the phases of the Red Sea Dipole (RSD). This connection was largely regulated by the upwelling associated with the local wind-stress-curl. Further, the spatial and temporal patterns of wind-driven upwelling (i.e., coastal and wind-stress-curl-driven upwelling) were reminiscent of the SST trend, highlighting the significant role of the upwelling mechanism in the SST budget and trend across the Red Sea. The positive phase of the RSD aligns with periods of stronger Toker Jet activity, reinforcing cold SST anomalies in the southern Red Sea due to enhanced upwelling-induced cooling. However, the impacts of wind-driven upwelling on local SST differ from region to region, highlighting the need to employ a high-resolution wind dataset in the simulation of SST across the Red Sea. Overall, our findings offer insights into the complex mechanisms and factors influencing SST variability in the Red Sea, thereby contributing to improving coastal zone management and environmental planning efforts.