Over the past weekend, many Canadians were surprised by unseasonably warm weather, with temperatures rising into the mid- to high-20s in various regions of the country, well exceeding typical seasonal norms. Popular beaches in Toronto and Ottawa saw a surge in visitors, an unusual scene for early October. Notably, the capital city set a heat record, hitting 29.9°C on Sunday, while Montreal also matched this temperature, breaking its own record.
The significant warmth is attributed to a large heat wave in the northern Pacific Ocean, influencing the shifting of the jet stream northward, as explained by Lualawi Mareshet Admasu, an atmospheric scientist at the University of British Columbia. This jet stream, a swift west-east airflow dividing cold northern air from warm southern air in the Northern Hemisphere, has been impacted by the elevated ocean temperatures, ushering warm air from southern or Equatorial regions into parts of Canada.
Geoff Coulson, a meteorologist at Environment and Climate Change Canada, noted that temperature records were shattered by more than five degrees, an exceedingly rare occurrence compared to the usual fractional or slight degree increases. The current marine heat wave mirrors the infamous “blob,” a prolonged period of warm water that significantly affected marine ecosystems and fisheries along the U.S. and Canadian west coasts starting in 2013.
Experts like William Cheung from the University of British Columbia warn that marine heat waves, exacerbated by global warming, are becoming more frequent and intense. The ocean’s capacity to absorb excess heat from greenhouse gas emissions continues to drive these changes, with temperatures in the northern Pacific presently nearly 2.5 degrees above pre-industrial averages.
Previous marine heat waves have had severe impacts on fisheries, such as the closure of the Pacific cod fishery in Alaska in 2020 and the abrupt collapse of the Bering snow crab fishery in 2018-19. Cheung emphasized the direct dependence of many individuals on the ocean for sustenance and livelihoods, urging proactive measures to address climate change to mitigate future environmental and economic losses.
While a cold front passing through Ontario and Quebec is expected to bring temperatures back to seasonal norms, researchers like Admasu anticipate a prolonged warmer-than-usual fall across North America due to the enduring effects of the Pacific heat wave. The ocean’s slower response to atmospheric changes suggests that these impacts may persist for an extended period, underscoring the ongoing influence of the warm ocean temperatures on regional weather patterns.