Many Canadians were greeted with unseasonably warm weather over the past weekend, with temperatures rising well above the typical fall range. In cities like Toronto and Ottawa, where beach visits are not the norm for early October, the mercury climbed into the mid- to high-20s. Notably, the heat in the nation’s capital shattered records, hitting 29.9°C on Sunday, a figure also matched in Montreal.
The heat surge has been linked to a significant heatwave in the northern Pacific Ocean, which has caused ocean temperatures to rise, influencing the movement of the jet stream. This narrow band of swiftly flowing air that separates cold northern air from warmer southern air has shifted northward, bringing unusually warm air from equatorial regions into parts of Canada.
According to Geoff Coulson, a meteorologist at Environment and Climate Change Canada, temperature records were shattered by more than five degrees, a rare occurrence as records are typically broken by much smaller margins. This warming trend, similar to the infamous “blob” phenomenon in 2013, is concerning experts like William Cheung from the University of British Columbia, who warn that marine heatwaves are becoming more frequent and severe due to global warming.
The absorption of excess heat by the ocean, driven by greenhouse gas emissions, is leading to a sustained increase in ocean temperatures. The current temperature anomaly in the northern Pacific, nearly 2.5 degrees warmer than pre-industrial levels, is a significant indicator of long-term climate changes. These rising ocean temperatures not only impact marine life but also have far-reaching consequences for local fisheries, as seen in recent years with closures and collapses of key fisheries due to declining fish populations.
As temperatures on land begin to return to seasonal norms with the passage of a cold front, experts anticipate a continued warm fall in North America due to the lingering effects of the ongoing marine heatwave. The slow response of the ocean to atmospheric changes suggests that these warm conditions may persist for some time, emphasizing the need for proactive climate change mitigation efforts.