Last weekend, many Canadians encountered unseasonably warm weather with temperatures rising into the mid- to high-20s across various regions of the country, significantly exceeding typical seasonal norms. Unexpectedly, individuals swarmed to beaches in Toronto and Ottawa at the start of October, as the nation’s capital set a heat record of 29.9°C on Sunday. Similarly, Montreal also hit 29.9°C on the same day, breaking its own record.
The prevailing warmth can be attributed to a substantial heat wave in the northern Pacific Ocean, as suggested by experts. According to Lualawi Mareshet Admasu, an atmospheric scientist at the University of British Columbia, the elevated ocean temperatures are driving the jet stream northward. The jet stream, a narrow high-speed air current flowing west to east across the Northern Hemisphere, serves as a boundary between cold air to the north and warm air to the south. While the intricate relationship between ocean heat waves and the jet stream is still being unraveled by scientists, Admasu notes that parts of Canada have experienced an influx of “very warm air from southern or Equatorial regions” as it shifts northward.
Geoff Coulson, a warning preparedness meteorologist at Environment and Climate Change Canada, highlighted that several temperature records were shattered by more than five degrees during this unusual weather event. Such significant deviations from the norm are rarely witnessed, with record-breaking occurrences typically limited to fractional or marginal increases.
The ongoing marine heat wave resembles the notorious “blob,” a persistent warm water mass that had a substantial impact on marine ecosystems and fisheries along the U.S. and Canadian western coastlines since 2013. William Cheung, the director of the Institute for the Oceans and Fisheries at the University of British Columbia, emphasized that global warming is exacerbating and escalating marine heat waves, leading to annual occurrences since 2019 post the “blob” event.
With the ocean absorbing about 90% of the surplus heat in the atmosphere, primarily due to greenhouse gas emissions from fossil fuel combustion, temperatures in the northern Pacific are currently nearly 2.5 degrees warmer than the pre-industrial average. This deviation is likely not momentary, as indicated by an analysis from the scientific group Berkeley Earth.
Previous marine heat waves have had severe repercussions on local fisheries, with instances such as the closure of the Pacific cod fishery off Alaska in 2020 due to diminished populations. Furthermore, the complete collapse of the Bering snow crab fishery, valued at over $200 million USD annually, occurred abruptly in 2018-19 following a 90% decline in numbers.
Cheung stressed the significance of the ocean to many individuals for sustenance, cultural practices, and livelihoods, underscoring the far-reaching impacts of marine heat waves on both marine life and human populations.
As temperatures normalize towards seasonal averages this week due to a cold front passing through Ontario and Quebec, experts remain vigilant regarding the relentless nature of the Pacific heat wave. Admasu anticipates a warmer than usual autumn across North America, emphasizing the prolonged effects of oceanic changes compared to atmospheric variations.
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