New research by NOAA shows that marine heatwaves can unfold deep underwater.

In an analysis of underwater temperatures of continental shelf waters surrounding North America dating from 1993 to 2019, scientists have discovered that marine heatwaves can be more intense and last longer than hot spells at the ocean surface.

In the depths of the ocean, these underwater heatwaves can occur without any signal of surface warming. Periods of anomalously warm ocean temperatures can have significant, detrimental impacts on marine life, coastal communities and the economy.

One example of this is “The Blob”, which is a marine heat wave, or a mass of warm water, that affects a large area of the northern Pacific along the coast of North America. It was first detected in 2013 and disrupted marine ecosystems and harmed fisheries.

The ocean absorbs approximately 90% of the excess heat from global warming, which has warmed around 1.1C above pre-industrial levels.