Strong upwellings of cool water from the depths of North America this spring.
That big blob of warm water in the middle of the Pacific Ocean grew steadily until reaching the Oregon and Washington coasts in July.
鈥淭his thing is covering most of the Northeast Pacific,鈥� said Andrew Leising, an oceanographer at the National Oceanographic and Atmospheric Administration in La Jolla, California.
Satellite imagery and detected the change.
Sea surface temperatures inside this blob are 5 to 7 degrees Fahrenheit above average.
鈥淭hat's not normal, by a far stretch,鈥� said University of Washington oceanographer Jan Newton, who runs a network of automated observatories off the Northwest coast. 鈥淲e should definitely be concerned.鈥�
Globally, oceans have hit record temperatures in 2023, with the surface of the world鈥檚 seas in April nearing an average of 70 degrees Fahrenheit, according to the University of Maine鈥檚 Climate Change Institute. Waters off Florida have reached freakish, bathtub-like temperatures, while seas from Japan to Greece have been hit by marine heat waves, and Antarctic ice has hit record-shattering lows, covering far less ocean than normal for the southern hemisphere winter.
鈥淔or us on the West Coast, we're not reaching record-breaking temperatures, but we're closing in on them,鈥� Leising said. 鈥淚t's kind of expected because we know the oceans have been warming at a slow but steady rate for decades now.鈥�
With carbon dioxide and other greenhouse-gas pollutants trapping more of the sun鈥檚 heat, we shouldn鈥檛 be surprised as temperatures head into uncharted territory, on land and at sea.
鈥淲e're going to just keep seeing, year after year, breaking record, breaking record, breaking record,鈥� Leising said.
A key question for the ocean heat wave now on the West Coast is whether it will stick around long enough to damage the food chain that creatures like seabirds, salmon, and humans rely on, as an extreme Pacific Ocean heat wave dubbed "The Blob" did in 2014 and 2015.
鈥淚n the Pacific Northwest, a lot of our organisms are used to pretty variable conditions because we have the upwelling/downwelling, where temperatures change rapidly according to the winds,鈥� Newton said. 鈥淏ut at some point, you can exceed tolerances.鈥�
Newton said much sea life is more sensitive to temperature changes than warm-blooded, land-based creatures.
鈥淔or humans, our air is warmer during the day, and it cools off at night, whereas an aquatic organism is in that [extra-warm] water all the time,鈥� she said.
鈥淎 lot of animals will just have a hard time. Even if the heat didn't bother them, they'll be bothered by not having food around,鈥� Leising said.
Courtesy Andrew Leising
Not all organisms fare worse in a heat wave, though.
Harmful, toxin-producing algae can thrive in warmer water, leading to impacts on other species and fisheries, as happened during a marine heat wave in 2022.
鈥淔irst it was razor clams, then it was mussels, then it was Dungeness [crabs]. So we had a series of shellfish closures all through the fall,鈥� Leising said.
The sea surface along the Northwest coast usually hits its peak temperatures in mid- to late August, according to Leising.
In recent years, Pacific Ocean heat waves 鈥� defined by how much they deviate from normal, rather than absolute temperature values 鈥� have lasted into mid-December, Leising said.
The impact of this heat wave could be amplified by the arrival of the climate phenomenon known as El Ni帽o, which leads to warmer water in much of the Pacific Ocean. In June, National Weather Service forecasters announced that El Ni帽o conditions had developed off the west coast of south America, reversing three years in a row of the opposite, La Ni帽a conditions.
El Ni帽os generally have little influence on the United States until late autumn.
鈥淓l Ni帽o is happening. But it's right now just limited to the equator region,鈥� Leising said.
El Ni帽o conditions this far north, on top of a persistent marine heat wave, could be a double whammy, leading to more record ocean temperatures, higher storm surges, and other impacts. Water expands as it warms, raising sea levels as it does.
Washington state climatologist Nick Bond said marine heat waves tilt the odds in favor of warmer weather on land in the Northwest.
鈥淭he meager snowpack of the winter of 2014-15 can be attributed in part to the extremely warm ocean temperatures that prevailed during the heyday of the "Blob," Bond said by email. 鈥淲e do not want that to happen again.鈥�
In July, the National Weather Service put the odds at more than 90% that El Ni帽o will continue through the Northern Hemisphere winter.
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