Seasonality of biological feedbacks on sea surface temperature variations in the Arabian Sea: The role of mixing and upwelling

Abstract

The effects of biological heating on upper-ocean temperature and circulation in the Arabian Sea are investigated using an ocean general circulation model. We find that the change of sea surface temperature (SST) is not only dependent on the variation of chlorophyll concentration, but also the dynamic processes, e.g., mixing and upwelling. Biological heating can warm the SST in the north Arabian Sea during spring and the central Arabian Sea during autumn when the mixed layer depth is shallow. However, the situation is quite different during winter and summer. Although the chlorophyll concentration is high in the north Arabian Sea during winter and in the western Arabian Sea during summer, the SSTs become significantly cool instead of warm. The heat budget analyses indicate that the cold SSTs result from both the strong convective mixing during the winter and the strong upwelling during the summer, which bring the cold water below the mixed layer to the surface.