The marine heat wave roiling the Pacific Ocean off the West Coast has weakened in intensity, shrunk in size and pulled away from shore, said scientists with the National Oceanic and Atmospheric Administration (NOAA).

“The coastal waters have cooled,” said Andrew Leising, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California. “The recent heat wave, it’s still there and it’s very strong, but it’s quite a ways offshore.”

Scientists feared this summer’s heat wave was a second coming of “The Blob,” which formed in 2014, peaked a year later with waters at close to 7 degrees above average and upended the West Coast’s marine ecosystem and food webs. Seabirds, sea lions and salmon died in huge numbers as marine temperatures soared.

This year’s heat wave may be shrinking and moving offshore, but it’s unclear whether it will persist, what effects the high surface temperatures have had on animals or how this will affect seasons to come. A Washington Department of Fish and Wildlife (WDFW) official said the agency was seeing odd creatures more typically found in warmer water and coho salmon runs were lower than forecast.

“We are not concluding it’s over yet,” said Chris Harvey, a Northwest Fisheries Science Center research biologist of the heat wave, adding that scientists will watch for the water-churning winter storms that could halt the unusual pattern. “We really need to see some good mixing events to stir the water up and let some of that heat dissipate into the atmosphere so the water this winter is as cold as it is during a normal winter.”

At its peak, this year’s event was the second-largest marine heat wave recorded, ranking below the now infamous “Blob,” Leising said.


Areas of warmer-than-usual water this year stretched from roughly Alaska to California.

Even now, somewhat diminished, the heat wave remains among the largest and most intense Leising has seen in nearly 40 years of data from satellite measures of sea surface temperatures in the Pacific.

The heat wave’s biological effects are being studied now.

“Counting the fish and seeing what species are out there takes weeks and months,” Leising said.

During “The Blob,” scientists documented strange happenings in Northwest waters.

Researchers caught tens of thousands of tubular, jellylike pyrosomes, which are usually found in the subtropics. Jellyfish populations shifted. Scientists hauled into their nets tropical fish, like the Pacific pompano.

This summer, fishers and researchers saw plenty of unusual happenings, said Larry Phillips, WDFW’s South Puget Sound and Coast Region Director.

A longtime Northwest fisherman called WDFW this summer and reported catching a species he’d never seen. He brought two to WDFW.


“They were called white croaker. They’re a species typically associated with California,” Phillips said. “They’re very uncommon in cooler water.”

The fisherman only kept two, but reported catching white croaker one after another.

Phillips said other species appeared in abundances “we hadn’t seen before,” listing yellowfin tuna, mahi mahi and bluefin tuna among the surprises.

“What does it mean? We don’t know what it means,” Phillips said. “I don’t know what normal is anymore. I don’t know if there will be such a thing as normal.”

Phillips said the agency had predicted a strong return of coho salmon this year.

Researchers “documented one of the highest densities of juvenile salmon off the coast we’d ever seen” in spring 2018, Phillips said. “Lo and behold, we didn’t see the return anticipated” this year when those juveniles were supposed to migrate back to Washington waters as adults in late summer.


The agency has had to close several coho fisheries earlier than expected because of poor returns. Phillips said WDFW also found undersized migrating coho in Puget Sound.

Phillips said the relationship between spring juvenile salmon counts and returning adults a year later has typically been a strong correlation. Not this time.

“Somehow that relationship fell apart. We ended up over-forecasting. That suggests marine survival affected those fish,” he said.

He suspects the marine heat wave, which peaked in August, might have played a role.

Scientists will be watching for Pacific storms this winter.

“Normally, we’d have these storms come in and churn everything up and reset the system,” Harvey said.

Leising said atmospheric models forecast a normal winter, which could dissolve the heat wave. But “those same models were completely wrong in 2013 and 2014,” Leising cautioned.


In 2013, the year before “The Blob” began to form, marine temperatures rose, before backing off as winter arrived.

Leising said the timing of this event appears to be similar to that of 2013.

“If that’s the case, we could be in for a really big event next year,” he said.

Leising said average ocean surface temperatures are rising and scientists may have to redefine what they consider a heat wave as the world warms.

But, he said, “the animals don’t care how we define it. The temperature is warmer than they’ve ever been. They’re still getting cooked.”