But an unusual mass of warm water nicknamed “the blob,” which appeared off Alaska and hung around through 2016, didn’t occur in isolation. In northern Australia in 2016, high ocean heat bleached hundreds of miles of corals, killed mangroves, and destroyed giant clams. Off New Zealand, an ocean hot spell wiped out black abalone and brought an oyster-killing disease.
Just as atmospheric shifts can bring droughts and nasty heat waves on land, shifts in weather or ocean circulation also can spark deadly marine heat waves, which can thoroughly scramble life at sea. But until recently scientists understood little about what role climate change might play in these extreme sea events.