Trans-Basin Interaction Sustains Multi-Year Marine Heatwaves in the Gulf of Alaska

Recent years have seen prolonged marine heatwaves (MHWs) in the Gulf of Alaska (GOA), affecting climate, ecosystems, and the economy. Our study shows that these multi-year MHWs consist of shorter episodes triggered by atmospheric wave trains from the tropical Pacific. These wave trains initiate MHWs in the GOA and propagate to the North Atlantic, causing sea surface temperature (SST) variations there. The SST changes in the Atlantic feedback to the Pacific, reactivating the wave train and triggering further MHWs in the GOA. This positive feedback loop, observed during the 2013-16 and 2018-22 MHWs, allows the North Atlantic to sustain and extend GOA MHWs into multi-year events. Our findings reveal that these MHWs are a trans-basin interaction phenomenon, sustained by a feedback loop between the North Pacific and North Atlantic. North Atlantic SST conditions may help forecast MHW duration in the Northeastern Pacific, potentially enhancing early warning systems and reducing their impacts.