Warm ocean temperature extremes—known as marine heatwaves—can dramatically impact the overall health of marine ecosystems around the globe; impacting the regional distribution of marine species, and altering primary productivity. There has been a considerable effort to characterize the timing, intensity, duration, and physical drivers of both individual and composite marine heatwaves events. However, marine heatwave research has primarily focused on sea surface temperature extremes. While surface marine heat waves can have dramatic impacts on marine ecosystems, extreme warming along the seafloor can also have significant biological outcomes.
In a new Nature Communications, authors Dillon Amaya, Michael Jacox, Michael Alexander, James Scott, Clara Deser, Antonietta Capotondi, and Adam S. Phillips use a high-resolution ocean reanalysis to analyze bottom marine heatwaves along the continental shelves of North America. The results of the study show bottom marine heatwaves intensity and duration varies strongly with the depth of the bottom floor, with typical intensities ranging from ~0.5 °C–3 °C. While bottom and surface marine heatwaves often co-occur, bottom marine heatwaves can exist without a surface marine heatwave, though that is found mostly in shallow waters.
Additionally, bottom marine heatwaves were found to be more intense and persist longer than surface marine heatwaves. As a result, the authors note it will be essential to maintain existing continental shelf monitoring systems and to develop new routine observational platforms, as well as ocean reanalyses, for real-time monitoring capable of alerting marine resource managers of ongoing bottom marine heatwave conditions.
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Image credit: NOAA