Many Canadians encountered unseasonably warm weather over the past weekend, with temperatures rising into the mid- to high-20s throughout various regions of the country, well surpassing typical seasonal norms.
Scores of individuals headed to beaches in Toronto and Ottawa, an unusual scene for early October, as the country’s capital set a new heat record, hitting 29.9 degrees Celsius on Sunday. Montreal also experienced a temperature of 29.9 degrees Celsius on the same day, shattering a previous record.
The elevated temperatures are attributed to a significant heat wave in the northern Pacific Ocean, according to experts. This anomalous warmth in the ocean is pushing the jet stream northward, as explained by University of British Columbia atmospheric scientist Lualawi Mareshet Admasu.
The jet stream, a narrow fast-flowing air current moving west to east across the Northern Hemisphere, acts as a boundary between cold air to the north and warm air to the south. While the complex relationship between ocean heat waves and the jet stream is still being studied, Admasu noted that parts of Canada are experiencing “very warm air from southern or Equatorial regions” as it shifts north.
Geoff Coulson, a warning preparedness meteorologist at Environment and Climate Change Canada, highlighted that several temperature records were broken by more than five degrees, an extremely rare occurrence. Normally, records are only broken by a fraction of a degree or a degree or two at most.
The current marine heat wave resembles the infamous “blob,” a multi-year expanse of warm water that significantly impacted marine life and fisheries along the U.S. and Canadian west coasts from 2013. Studies suggest that marine heat waves are becoming more severe and frequent due to global warming, according to William Cheung, director of the Institute for the Oceans and Fisheries at the University of British Columbia.
With the ocean absorbing about 90% of the excess heat in the atmosphere, temperatures in the northern Pacific are nearly 2.5 degrees warmer than the pre-industrial average this year, indicating a likely long-term trend rather than a short-term fluctuation.
Past marine heat waves have had devastating effects on local fisheries, such as the closure of the Pacific cod fishery off Alaska in 2020 and the collapse of the Bering snow crab fishery in 2018-19, worth over $200 million annually. Cheung emphasized the direct dependence of many people on the ocean for sustenance, cultural practices, and livelihoods.
As temperatures are expected to return closer to seasonal averages due to a cold front moving through Ontario and Quebec, researchers anticipate a persistently warm fall in North America due to the ongoing Pacific heat wave, which shows no signs of relenting.