November 11, 2019 — The following was released by NOAA Fisheries:
The vast marine heatwave that spread warm temperatures across the northeast Pacific Ocean late in the summer and fall of 2019 has declined in size and pulled back from the West Coast, possibly reducing its immediate impacts on coastal ecosystems.
It has declined to about half the size and intensity it displayed in August. However scientists caution that the heatwave designated MHW NEP19a remains two to three times the size of Alaska and still retains enormous amounts of heat in the upper layers of ocean. It remains one of the top four or five largest heatwaves on record in the North Pacific in the last 40 years.
“What we are seeing now is a smaller heatwave that is farther offshore, but there is still a very large span of the Pacific Ocean that is much warmer than usual,” said Andrew Leising, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center (SWFSC) in La Jolla, California. Leising has developed criteria to detect and gauge the size and magnitude of marine heatwaves. “The question is, where does it go from here? That’s what we’re watching now.”
The edge of the heatwave is now about 1,500 kilometers (about 930 miles) from the West Coast, but still envelops much of the Gulf of Alaska. It no longer so closely resembles the enormous earlier marine heatwave known as “the Blob” that affected much of the West Coast through 2014 and 2015, causing reverberations through the food web.
Low salmon returns to many West Coast rivers in the last few years have been linked to the Blob, which reduced the availability of food when the salmon first entered the ocean as juveniles.