Marine heat waves in the Southeast US: Climatology, trends, and connections to humid heat stress

Marine heat waves (MHWs), which can have devastating impacts on marine ecosystems, are characterized by prolonged warm ocean heat content anomalies over a large region such as the Gulf of Mexico or North Atlantic Ocean. MHWs in waters adjacent to the Southeast U.S. have increased in frequency, intensity, duration, and spatial extent over time. During MHWs in adjacent waters, evaporation and therefore atmospheric water vapor concentrations may increase over nearby land masses, acting to amplify humid heat stress, particularly in coastal areas such as the Gulf Coast and Florida Peninsula. This study first establishes a 40-year climatology (1985-2024) of MHW events in waters adjacent to the Southeast U.S., using the NOAA Coral Reef Watch gridded dataset. Next, trends in MHW frequency, duration, and spatial extent are elucidated and tested for statistical significance. Finally, connections between MHWs and Southeast U.S. humid heat stress events are explored, with a focus on extreme heat stress events and physical linkages. Project results will increase understanding of how MHWs have changed near the Southeast U.S. and how they may amplify humid heat in coastal regions with large and increasing populations.