'The Blob,’ a Marine Heatwave, Kills Millions

The presumed victims of an unprecedented marine heatwave in the Pacific are a million seabirds that died along the US west coast. This is expected to become more frequent due to climate change.

The most successful seabirds in the Northern Hemisphere, common murres can crisscross vast expanses of the ocean faster than any other northern seabird and can dive the length of two American football fields to snatch small fish.

After nearly one million common murres died at sea and washed ashore from California to Alaska in 2015 and 2016, scientists blame an unexpected squeeze on the ecosystem's food supply, caused by a severe and long-lasting marine heatwave known as 'the Blob.'

The findings were published Jan. 15 in the journal PLOS ONE. According to author Julia Parrish, a UW professor in the School of Aquatic and Fishery Sciences, one could compare it to a run on the grocery stores at the same time that the delivery trucks stopped coming to the stores.

She linked the "relatively new" increased frequency of such heat waves to climate change.

The number of birds - many of breeding age - killed over a geographic area the size of Canada was deemed by scientists "unprecedented and astonishing."

"The most powerful marine heatwave on record," which ran from 2014 to 2016, created a mass of seawater known as "the Blob" which coincided with the warmed Pacific of an El Nino period.

According to researchers from the U.S. Geological Survey, the die-off was caused by depleted food supplies, triggered by above-average sea temperatures between 2013 and 2016.

The marine heatwave started in late 2013 when a patch of warm water later nicknamed "the Blob" formed off the Alaskan coast that swelled to incorporate parts of the Pacific Coast as far south as Mexico.

About 62,000 common murres (Uria aalge) washed ashore from summer 2015 to spring 2016 between Alaska and California, so researchers extrapolate that this means around a million died in total.

John Piatt from the US Geological Survey questioned how a million can die over 6000 kilometers at the same time, and what caused it.

It was reported in PLOS ONE that an estimated 10 to 20 percent of the region's total population was wiped out.

The Blob caused sea surface temperatures along the Pacific coast of North America to rise by 1-2°C. The fish that common guillemots normally eat, such as herring, sardine, and anchovy, either died or moved into cooler waters elsewhere, leaving the guillemots to starve.

The Blob reached 6 degrees Celsius above typical maximum temperatures in places and extended to a depth of 200 meters, and more than 3,000 kilometers up the US coastline into Alaska.

While the Blob persisted off the coast of the US, production of phytoplankton or microscopic algae dropped and "the largest harmful algal bloom in recorded history" stretched from California to the Gulf of Alaska in 2015.

A high-pressure ridge calmed the ocean waters; heat stayed in the water, without storms to help cool it down.

The few degrees of warming caused a massive bloom of harmful algae along the west coast, which killed many animals and cost fisheries millions of dollars in lost income.