Suppression of marine heatwave activity by tropical cyclone–induced upper ocean cooling

Marine heatwaves (MHWs) have drawn substantial scientific attention due to their profound biological and economic impacts, especially in the context of climate change. This study highlights the crucial role of tropical cyclones (TCs) in disrupting MHWs by altering ocean temperatures. As demonstrated by Tropical Cyclone Bavi, intense sea surface temperature (SST) cooling, reaching up to 7°C, immediately terminated a mature MHW and suppressed subsequent MHW development for up to 8 months. More generally, on the basis of post-TC MHW cases (reoccurring within 1 month) during 2014 to 2023, we found that MHW disruption duration is proportional to the magnitude of TC-induced SST cooling, ~5 to 7 days per degree of cooling. At a broader scale, a 20-year (2004 to 2023) analysis revealed 99% significant inverse relationships between seasonal MHW and TC activity. These findings suggest that TCs can act as natural regulators, effectively mitigating heat stress from MHWs and potentially serving as a lifeline for marine ecosystems.