Newly published research says climate change is making familiar winter activities on frozen lakes and rivers more dangerous.
An analysis of thousands of winter drownings from around the world shows that risks increase dramatically as air temperatures near zero — exactly what has been happening as the greenhouse effect takes hold, said lead author Sapna Sharma of York University in Toronto.
"Years with warmer winters corresponded to more drownings," Sharma said.
Research that correlated more than 4,000 winter drownings from 10 countries found that water deaths have increased over the last 30 years, she said.
"We know that the last 25 years are the fastest-warming years in the last 150 in terms of lake ice being lost. In the spring, the ice melts earlier, and that's when people are using the ice a lot."
She and her colleagues found that drownings increased exponentially as air temperatures nudged upward but ice didn't necessarily thaw. The most dangerous times were when the weather hovered between -5 C and 0 C.
Unpredictable and atypical weather of the type associated with climate change also makes ice more dangerous, said Sharma.
Freeze-thaw events can reduce the structural integrity of ice. Rain turns the top layer to slush, which, when it refreezes, becomes what is called grey ice.
"It becomes weaker and doesn't hold as much weight," Sharma said.
Even heavy snow can pose a threat. Its weight can decrease ice strength and its insulating ability can preserve unfrozen layers.
The impacts of climate change on sea ice are familiar. Inuit people have for years said their trusted winter travel and hunting routes are becoming unpredictable and dangerous.
Sharma said the same thing is happening on freshwater.
She points out that long-standing winter events in Europe, such as Sweden's Vikingaslingan skating race, have had to be repeatedly cancelled because of poor conditions. Ice fishing derbies in Minnesota — which draw thousands of participants and offer big cash prizes — are no longer dependable.
"All of these important cultural activities are being lost in warmer winters."
Sharma worries COVID-19 could make this winter more dangerous.
"More people are spending more time outside and some people maybe for the first time," she said.
"There's a risk associated with using ice. You don't want to look at the forecast just for today or the weekend. Get an idea of what happened in the last month. That will tell you what the structural integrity of the ice might be."
This report by The Canadian Press was first published Nov. 18, 2020.
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