Marine Heatwave (MHW)

A marine heatwave is a prolonged period (five or more days) of anomalously warm sea surface temperature, typically above the local seasonal 90th percentile. Events such as the 2013-16 northeast Pacific Blob and successive Mediterranean and Tasman Sea events have killed kelp forests, bleached corals, and shifted fisheries. Their frequency, duration, and intensity have risen with ocean warming, and they are now forecast and categorized much like atmospheric heatwaves.