Warmer winters causing more ice-free lakes in northern hemisphere, study finds

Climate change is having a widespread effect on lakes in the northern hemisphere, according to a new study.

The study, published in the journal Geophysical Research Letters, examined 122 lakes from 1939 to 2016 in North America, Europe and Asia, and found that ice-free years have become more than three times more frequent since 1978.

These ice-free years not only threaten the livelihoods of the people who depend on them, but they also have the potential to cause profound ecological impacts.

“Ecologically, the ice acts like a reset button,” said Sapna Sharma, study co-author and associate professor in the biology department at York University in Toronto.

“The years when you don’t have an ice cover, the water temperatures are warmer in the summer. There is a higher likelihood of algae blooms, some of which can be toxic. And it can really affect spawning periods and may affect fish populations under the ice. “

Aerial view of melting permafrost tundra and lakes near the yupik village of Quinhagak in the Yukon Delta of Alaska April 12, 2019. (Mark Ralston / AFP / Getty Images)

There are also concerns in the Arctic, where warming is happening three times faster than anywhere else in the world. And with more warming, there is more permafrost thawing, which can affect water quality in northern communities.

“One of the impacts is on the hydrology of the region,” said Claude Duguay, professor at the University of Waterloo and holder of a university research chair in cryosphere and hydrosphere from space, who did not participate in the study.

“When you have catastrophic drainage from these lakes, of course, they disappear. And they won’t necessarily reform as we reach higher temperatures. The impact for communities can be on food security. So you think of trapping, hunting, fishing, as well as the availability of water for the communities.

Of the millions of lakes in the world, the study suggests that more than 5,000 of them could be ice-free by the end of the century.

Dramatic changes

The authors found that ice-free years were more common in the second half of their study period. While there had been only 31 ice-free events before 1978, there were 108 after that year.

One of the oldest records preserved on lake ice is that of Lake Suwa near Nagano, Japan, which dates back to 1443, kept by Shinto priests. The study found that instead of freezing every year, it now freezes on average twice a decade.

“In the next 10 years, this may be the last time the lake freezes again,” Sharma said.

These changes in the lakes are likely to continue for decades as the planet warms due to the continued release of greenhouse gases into the atmosphere, the authors say.

Sapna Sharma, study co-author and associate professor in the biology department at York University in Toronto, says lakes that don’t freeze in winter have repercussions in summer, such as algae blooms that threaten them. fish and other fauna. (Craig Chivers / CBC)

The lakes most at risk are those that are deep because it is more difficult for them to form ice, especially the Great Lakes, Sharma said.

And it’s not just about the quality of the water; it’s also a question of quantity, she noted. Ice helps reduce the rate of evaporation, so without this essential ice cover, evaporation rates can increase and reduce the amount of fresh water available.

Alex Mills, a York University professor who studies ice phenology and was not involved in the research, has seen the change himself, especially on Lake Simcoe in Ontario.

“The general trend is pretty clear and it’s been around 1850, the lake is now freezing about two weeks later than before, and it’s thawing about a week earlier than before,” he said. “And so if you add that up, there’s ice on the lake here about three weeks less a year than before. So that’s a pretty dramatic change.”

Mills said Barrie, a town on the shores of Lake Simcoe, had an annual carnival in Kempenfelt Bay every winter until the 1970s. Then someone fell through “and that was it,” a- he declared. “We have never had a carnival on the lake since then.”

While it’s likely more lakes will experience freer ice-free winters, Sharma said she believes that with more research and solutions, there is still hope.

“I went to [United Nations climate change conference] meetings, and there are so many young people who care about climate change dedicating their professional lives to doing something about it. And people have very creative solutions, ”she said.

“I think in the next 20 or 30 years if we can get that support to find out [the] the climate is changing and it’s affecting us now and we have to do something now – if we mobilize people for that, I think we can make a difference. “

About Lucille Thompson

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