Deep Impact: Heat Waves Happen at the Bottom of the Ocean Too

...The 2013-2016 marine heat wave known as “The Blob” warmed a vast expanse of surface waters across the northeastern Pacific, disrupting West Coast marine ecosystems, depressing salmon returns, and damaging commercial fisheries. It also prompted a wave of research on extreme warming of ocean surface waters.

...But, as new research from the National Oceanic and Atmospheric Administration (NOAA) shows, marine heat waves also happen deep underwater.

...About 90% of the excess heat from global warming has been absorbed by the ocean, which has warmed by about 1.5C over the past century. Marine heatwaves have become about 50% more frequent over the past decade.

...The research team, from NOAA, Cooperative Institute for Research in Environmental Sciences (CIRES), and National Center for Atmospheric Research (NCAR), found that on the continental shelves around North America, bottom marine heat waves tend to persist longer than their surface counterparts, and can have larger warming signals than the overlying surface waters. Bottom and surface marine heat waves can occur simultaneously in the same location, especially in shallower regions where surface and bottom waters mingle.

...Unusually warm bottom water temperatures have also been linked to the expansion of invasive lionfish along the southeast U.S., coral bleaching and subsequent declines of reef fish, changes in survival rates of young Atlantic cod, and the disappearance of near-shore lobster populations in southern New England...more