View of the El Arco rock formation at the Pacific Ocean in Cabo San Lucas, Baja California state, Mexico on August 4, 2023.ALFREDO ESTRELLA/AFP/Getty Images
Scientists are monitoring a large marine heat wave that has warmed some parts of the Pacific Ocean 5 C above normal and is approaching the Canadian and U.S. west coasts.
Andrew Leising, a research oceanographer with the U.S. National Oceanic and Atmospheric Administration, said the heat wave formed in the Northeast Pacific in mid-May and grew in size as it advanced toward British Columbia, Washington State and Oregon. It is now roughly four million square kilometres and 200 kilometres away from land.
Dr. Leising described the event as significant but not extreme, noting there have been marine heat waves of similar size, duration and intensity in recent years. The wild card, he said, is the looming El Niño, the recurring climate phenomenon known for playing havoc with ocean and atmospheric conditions around the Pacific and beyond.
“The last time we had a large heat wave like we’ve got right now, and had El Niño looming along the equator, that was in 2014, and that led to ‘the blob,’” he said, referencing the prolonged marine heat wave that created huge blooms of harmful algae and shuttered fisheries up and down the coast.
“So it leaves you to speculate: Will we have in 2024 another whole Pacific Northwest region-spanning ‘blob’ like we did in 2015? It’s not out of the realm of possibility that we get another large heat wave that lingers through the winter.”
El Niño, the climate wild card, is back. Scientists are racing to predict its impact on Canada
Dr. Leising said marine heat waves of recent years have followed a pattern of building up far offshore in the spring, growing as they approach coastal waters in the summertime, and receding from the coastline by October or November.
“The best-case scenario will be that the heat wave we have now will back off like it has the last several years, we have a little bit of return to normal during November, December, January, but then it’s followed by the El Niño,” he said, noting that this scenario could still have a cumulative effect on marine animals.
“The worst-case scenario would be that the El Niño weather patterns that develop on the equator affect the atmosphere in the North Pacific and it reinforces and maintains the heat wave, so that it does not recede from the coast as much as it has in recent years. I think that is less likely, but possible.”
The U.S. Climate Prediction Center says there is a 90-per-cent chance El Niño will continue through the Northern Hemisphere winter, peaking with moderate to strong intensity between November and January.
The summer that climate heating metastasized
The approaching marine heat wave comes during a summer of extremes. Across Canada, 133,000 square kilometres of land have burned, making 2023 the country’s worst wildfire season. On Tuesday, the European Union’s Copernicus Climate Change Service said July was the hottest month globally since record-keeping began in 1940. In late July, water temperature near the southern tip of Florida reached 38.4 C – hot-tub temperature.
Meanwhile, Environment Canada is tracking a “very strong atmospheric signal” that is expected to bring air temperatures of more than 10 degrees above seasonal to the West Coast by late weekend and early next week.
“It’s going to be across Oregon, Washington and mostly southwestern B.C. to start, and then evolve up the coast into, maybe into the north coast,” said warning preparedness meteorologist Armel Castellan.
“I think the saving grace, in some ways, is that we’re seven weeks after the solstice. It doesn’t compare to what we saw in 2021, because we now have much longer nights compared to then. But we are looking at a sizable anomaly for the temperatures.”