Last weekend, numerous Canadians encountered unseasonably warm weather, with temperatures rising into the mid to high 20s in various regions, well exceeding typical seasonal norms. In Toronto and Ottawa, individuals swarmed to beaches, an uncommon sight for early October, as both cities shattered heat records, hitting 29.9°C on Sunday. The warmth has been attributed to a significant heatwave in the northern Pacific Ocean.
Lualawi Mareshet Admasu, an atmospheric scientist at the University of British Columbia, explains that the abnormally warm ocean temperatures are driving the jet stream northward. The jet stream, a swift, west-east air current over the Northern Hemisphere, serves as a boundary between colder northern air and warmer southern air. As the jet stream shifts north, Canada experiences a flow of warm air from southern or Equatorial regions, leading to the recent heat surge.
Geoff Coulson, a warning preparedness meteorologist at Environment and Climate Change Canada, notes that temperature records were shattered by more than five degrees, an exceptionally rare occurrence. This contrasts with typical record-breaking instances of mere fractions or one to two degrees.
The ongoing marine heatwave echoes the infamous “blob,” a prolonged period of warm water from 2013 that significantly impacted marine life and fisheries along the U.S. and Canadian west coasts. William Cheung, director of the Institute for the Oceans and Fisheries at the University of British Columbia, highlights that global warming is exacerbating and increasing the frequency of marine heatwaves. Since the “blob,” marine heatwaves have occurred annually since 2019, indicating a worrying trend towards more intense and frequent heatwaves if climate change mitigation efforts fall short.
The ocean plays a crucial role in absorbing about 90% of the excess heat in the atmosphere, largely stemming from greenhouse gas emissions. Current temperatures in the northern Pacific Ocean stand nearly 2.5 degrees above pre-industrial averages, suggesting a sustained warming trend rather than a short-term anomaly.
Previous marine heatwaves have had severe repercussions on local fisheries, with instances like the closure of the Pacific cod fishery off Alaska in 2020 due to declining numbers. Cheung emphasizes the direct and indirect impacts of marine heatwaves on communities reliant on the ocean for sustenance, culture, and livelihood.
As temperatures normalize this week due to a cold front passing through Ontario and Quebec, Admasu foresees a continued warm autumn in North America. The lingering effects of the Pacific heatwave are expected to persist, underscoring the importance of ongoing monitoring and research efforts.
In summary, the recent warmth in Canada is linked to a significant heatwave in the northern Pacific Ocean, with implications for weather patterns and marine ecosystems. Efforts to mitigate climate change are vital in addressing the escalating frequency and intensity of marine heatwaves and their far-reaching consequences.
