In 2013, a monstrous marine heatwave known as 'The Blob' developed off the coast of Alaska and soon stretched as far south as Mexico along the Pacific coast of North America.
It lingered far longer than anyone expected, decimating fisheries, triggering toxic algal blooms, disturbing kelp forests, and starving sea birds of food.
At one point, a buoy bobbing atop the ocean near Oregon detected frightening jumps in temperature of up to seven degrees Celsius in less than an hour. The ocean was sweltering.
But scientists, with their attention fixed on temperature data streaming in from ocean surfaces, had little idea what was transpiring in the depths below.
Now, new modeling led by researchers at the US National Oceanic and Atmospheric Administration (NOAA) shows that marine heatwaves can unfold deep underwater, too – sometimes in tandem with heatwaves that ripple across the ocean surface or else when there is no detectable warming signal above.
The new analysis, of continental shelf waters surrounding North America, also finds these so-called bottom marine heatwaves can be more intense and last longer than hot spells at the ocean surface, though it varies from coast to coast.
"Researchers have been investigating marine heat waves at the sea surface for over a decade now," says lead author Dillon Amaya, a climate scientist with NOAA's Physical Science Laboratory.
But they have been limited to the cache of data on temperature extremes at the ocean surface, logged by floating buoys or detected by ships or overhead satellites. It's much harder to probe ocean temperatures further down the water column and along continental shelves.
Some data exist, but the researchers behind this latest study mostly had to extrapolate from ocean surface observations, inputting that data into computer models to simulate ocean currents that upwell from the deep, bringing essential nutrients to coastal waters. READ MORE...
