A giant marine heatwave has descended on Alaska

An area of unusually warm water is growing off the west coast of North America, stretching from Alaska and Canada to California.

It’s the second largest marine heatwave of its kind, according to the US National Oceanic and Atmospheric Administration (NOAA). The largest was in 2014: nicknamed “the Blob,” it covered an area from Mexico to Alaska.

The 2014 event was blamed for sparking warmer weather on land, depleting salmon food stocks and causing the sudden deaths of around 30 whales in the Pacific. Those deaths were most likely to have been brought on by the whales ingesting toxic algae, created by the warming ocean. Back then, temperatures in the water peaked at 3.9°C above average.

Return of ‘the Blob’?

So far, this year’s “Blob” – officially known as the Northeast Pacific Marine Heatwave of 2019, or NEP19 – has had a warming effect of more than 2.7°C in the waters off the coast of Washington state.

Andrew Leising and Steven Bograd, research scientists at NOAA Fisheries’ Southwest Fisheries Science Center in California, are tracking and measuring the heatwave.

“Coastal upwelling of deep, cold water has kept the warm expanse mostly offshore, although it appears to have come ashore in Washington and could do so in other areas as upwelling wanes in the fall,” they say. “If atmospheric conditions persist and NEP19 moves into nearshore coastal waters, it is likely to have impacts on coastal ecosystems this fall.”

The NOAA believes the marine heatwave started when a ridge of high pressure weakened winds that would normally have cooled the surface temperature of the ocean. It says the size and scale of NEP19 could rival the 2014 Blob.

The agency also highlights a pattern of warmer water that could indicate longer-term changes to the marine climate. It has identified a band of unusually warm high pressure stretching north to the Bering Sea and Alaska in recent years.

Real and present danger

“Given the magnitude of what we saw last time, we want to know if this evolves on a similar path,” says Chris Harvey, a research scientist at the NOAA’s Northwest Fisheries Science Center.

Coastal waters are important marine ecosystems – feeding and breeding grounds for thousands of different animals. Their habitat is at risk of being damaged by NEP19, repeating what happened in 2014.

But the threat posed by warming oceans across the globe is even greater than that.

Approximately half of all our oxygen is generated by phytoplankton – tiny plant-like organisms that live in the ocean. They also consume carbon dioxide, transferring about 10 gigatonnes of carbon from the atmosphere deep into the ocean each year.

Anything that disrupts life for the phytoplankton could easily disrupt our lives too.

Warming seas are also believed to be responsible for coral bleaching, wiping out all life across entire reefs. Added to which, warming oceans can start to create a vicious cycle of associated problems – greater and more volatile storms, increased deoxygenation, and more.