Intensifying concurrent marine–atmospheric heatwaves in the marginal seas of the Arabian Peninsula: implications for coral bleaching and ocean productivity

Abstract Marine (MHWs) and atmospheric heatwaves (AHWs) are intensifying with climate change, but their co-occurrence as concurrent heatwaves (CHWs) poses an even greater threat to marine ecosystems. This study examines the spatiotemporal variability, physical drivers, and ecological impacts of CHWs across the marginal seas of the Arabian Peninsula from 1982 to 2021. CHWs are most frequent in the northern Red Sea, Arabian Gulf, and western Arabian Sea, and least common in the southern Red Sea. Their frequency and duration have increased significantly, by up to 7.5 days per decade in the northern Red Sea. CHWs extend the duration of MHWs and AHWs by an average of 6 and 2.2 days, respectively, compounding ecological stress. Our findings show that CHWs are the dominant drivers of coral bleaching and productivity loss in the region, with 80–85% of severe bleaching events linked to CHWs. They also triggered more than 20% decline in chlorophyll-a concentrations – nearly 1.4 times that of standalone MHWs. These results underscore the critical role of atmospheric heat in marine impacts. Case studies from 1998 and 2010 highlight the influence of high-pressure anomalies and weakened winds in shaping the widespread CHWs. The study calls for integrating CHW risks into conservation strategies to build ecosystem resilience in a warming climate.