SOURCE: Inside Climate News

DATE: September 18, 2019

SNIP: An intensifying marine heat wave in the northeastern Pacific Ocean has triggered government warnings about harm to salmon and other fisheries along the U.S. West Coast, and it’s raising concerns about hurricane risks to the Hawaiian islands and wildfire risks in California.

The current marine heat wave covers a horseshoe-shaped area about the size of Alaska. It extends from the Gulf of Alaska down the coast of Western North America and westward to Hawaii. In the warmest areas, sea surface temperatures have reached about 5.4 degrees Fahrenheit above average.

Marine heat waves occur when sea surface temperatures in part of the ocean rise and stay above the expected seasonal temperatures for at least five days in a row. Scientists say these heat waves are forming more frequently, and they suspect that shifts in winds and ocean currents driven by global warming are a big part of the cause.

A 2018 study showed that, since 1925, marine heat waves have become 34 percent more frequent and they are lasting longer. The majority of marine heat waves, about 87 percent, can be attributed to human-caused global warming, the authors found.

The National Oceanic and Atmospheric Administration is tracking the current marine heat wave and has warned of disruptions to ocean ecosystems and fisheries along the West Coast.

Andy Leising, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California, said this year’s warm blob could be as strong as the last and is already one of the most significant marine heat waves on record in the region because of its size and intense warmth.

So far, upwelling—vertical currents of cool water rising to the surface near the coast—has kept the heat from reaching the coast, but the winds that drive the upwelling there often die down in the fall. That has already started happening along the coast of Washington, where the warm water is starting to affect temperatures on land.