Persistent 2024 warm‐season marine heatwave in the Kuroshio extension region under global warming

In 2024, the Kuroshio Extension (KE) region experienced a prolonged marine heatwave (MHW), intensifying during the warm season and peaking in mid-August. Mixed-layer heat budget analysis reveals that the onset was primarily driven by anticyclonic eddies associated with a northward-shifted KE axis and enhanced shortwave radiation due to atmospheric blocking. This was further amplified by an eastward-propagating Eurasian teleconnection wave train triggered by North Atlantic sea surface temperature (SST) anomalies. The decay phase was dominated by eddy activity and wind–evaporation–SST feedback. Attribution analysis shows that such an event would have been unlikely without anthropogenic forcing, with approximately 35% of its magnitude attributed to atmospheric circulation, and the remaining 65% to thermodynamic warming and oceanic internal dynamics. These results highlight the increasing likelihood of persistent MHWs in dynamic western boundary current regions under climate change, emphasizing the need for enhanced predictive tools and targeted adaptation efforts.

Plain Language Summary

Marine heatwaves (MHWs), defined as prolonged periods of anomalously warm sea surface temperatures (SST), are increasing in frequency and intensity under climate change. This study examines a persistent MHW that occurred in the Kuroshio Extension (KE) region during the 2024 warm season, maintaining strong intensity over an extended duration. During the onset phase, a northward-displaced KE axis generated anticyclonic eddies that transported warm subtropical waters northeastward. Concurrently, reduced cloud cover induced by an atmospheric blocking enhanced shortwave radiation, intensifying surface warming. This was further linked to an eastward-propagating Eurasian Rossby wave train triggered by North Atlantic SST anomalies. In the decay phase, anomalous westerly winds enhanced latent heat loss and suppressed warming through wind–evaporation–SST feedback. Attribution analysis indicates that approximately 35% of the event's intensity can be attributable to atmospheric circulation anomalies, while the remaining 65% is linked to anthropogenic warming and oceanic internal dynamics. These results highlight the combined roles of oceanic and atmospheric processes in driving MHWs in western boundary current regions. Improved understanding of these mechanisms is essential for enhancing prediction capabilities and informing early warning and adaptation strategies under continued climate change.