Drivers of marine heatwaves in coral bleaching regions of the Red Sea

Extreme warm ocean temperature events, known as marine heatwaves, have been associated with several coral bleaching reports in coastal locations of the Red Sea. Yet, our knowledge of the processes driving these events remains limited. Here we analyse the upper ocean mechanisms behind multiple summer marine heatwaves between 2001 and 2015, over known coral bleaching-affected regions, using a high-resolution ocean model, specifically tuned for the Red Sea. Our findings indicate atmospheric forcing as the primary driver of marine heatwave onsets in the northeast and southwest, while horizontal advection plays a key role in the southeast and northwest coasts. While the frequency and associated temperature changes of the events’ main drivers are subject to regional influences, the intensity and duration of extreme warming due to horizontal advection, on average, exceed that of atmosphere heat fluxes, which act as the major cooling mechanism across the majority of study areas. Ecological threats for Red Sea corals are further highlighted with a view to enhance our understanding of their response to climate change. Atmospheric forcing governs summer marine heatwave onsets in the northeast and southwest Red Sea, whereas horizontal advection is key in the southeast and northwest, according to high-resolution ocean model simulations.