One of Ontario’s worst polar vortices in over a decade struck the Waterloo Region on Jan. 20. Temperatures in certain areas of southern Ontario plunged to as low as -30 C. A polar vortex is a jet stream located around 10 kilometres above the ground. Chris Fletcher, chair and associate professor in the geography and environmental management department, said the yearly winter occurrence of these phenomena typically encircle the Arctic in a narrow zone, but it can become twisted or wavy and move southward outside the Arctic and down over North America. “There are many factors that can combine to cause the jet stream to distort, and scientists don’t have a very reliable way to predict these events more than a few days in advance. This is the subject of much ongoing research by climate scientists,” he said. 

When asked about how the current polar vortex compares to past events, Fletcher expressed that the week of Jan. 20th was a particularly cold event, possibly the coldest air mass in KW in 5 to 10 years. He noted, “Overall, severely cold weather is becoming demonstrably less common as the climate has warmed by 1-2 degrees C over the past 100 years. The trend toward less severe winters is a very well understood and predictable consequence of climate change.” 

When asked about the potential long-term impacts of such extreme cold temperatures on local ecosystems, Fletcher said, “These kinds of temperatures are not particularly unusual in January in Ontario, and so the natural ecosystems are well adapted to deal with them for short spells. The bigger challenge is to humans, particularly those who are the most vulnerable in our society, such as the unhoused, elderly, and small children.” He continued to explain that there is a risk associated with these types of events becoming less frequent in a warming climate, namely that we would lose our knowledge of how to deal with them. Although these kinds of long-range weather projections are still highly unclear, Fletcher noted that it’s likely that the climate factors coupled to cause the jet stream to shift southward might have additional effects on temperature or precipitation.