A new study has found that climate change has a large-scale effect on lakes in the northern hemisphere.
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 three times as frequent since 1978.
These ice-free years not only threaten the livelihoods of the people who depend on them, but also have the potential to cause profound environmental impacts.
“Ecologically, ice acts as a reset button,” said Sapna Sharma, co-author of the study and associate professor in the biology department at York University in Toronto.
“In years you do not have ice cover, water temperatures are warmer in summer. There is a higher probability of algae flowering, some of which can be toxic. And it can really affect the breeding time and can affect the fish population under the ice. . “
There is also concern in the Arctic, where warming is three times faster than anywhere else in the world. And with higher heating, there is more permafrost thawing, which can affect water quality in northern communities.
“It has an impact on the region’s hydrology,” said Claude Duguay, a professor at the University of Waterloo and chair of cryosphere and hydrosphere research in space, who was not involved in the study.
“When you have catastrophic drainage of these lakes, of course, they disappear. And they will not necessarily reform as we reach higher temperature conditions. The impact for communities can be on food security. as well as water availability for 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 were only 31 ice-free events before 1978, there were 108 after that year.
One of the oldest preserved records of lake ice is that of Lake Suwa near Nagano, Japan, dating from 1443, preserved by Shinto priests. The study found that instead of freezing annually, it now freezes on average twice a decade.
“In the next 10 years, it may be the last time the lake freezes again,” Sharma said.
These changes to the lakes, the authors say, are likely to continue for decades as the planet warms due to the continued release of greenhouse gases into the atmosphere.
The lakes most at risk are the deep ones, because it is more difficult for them to form ice, especially the Great Lakes, Sharma said.
And it’s not just about water quality; it’s also about quantity, she remarked. Ice helps reduce the evaporation rate, so without that essential ice cover, evaporation rates can increase and reduce the amount of fresh water available.
Alex Mills, a professor at York University who studies ice phenology and has not been involved in research, has seen the change himself, especially on Lake Simcoe in Ontario.
“The general trend is pretty clear, and that’s since around 1850, the lake now freezes two weeks later than it melts and thaws about a week earlier than before,” he said. “So, if you add them, there is ice on the lake here about three weeks less a year than before. So this is a pretty dramatic change. “
Mills said Barrie, a town on the shores of Lake Simcoe, used to have an annual carnival in Kempenfelt Bay every winter until the 1970s. Then someone fell through “and that was it,” he said. “I haven’t had a carnival on the lake since.”
Although more lakes are likely to see more winters without ice, Sharma said she believes that with more research and solutions, there is still hope.
“I was at [United Nations climate change conference] meetings and there are so many young people who care about climate change who dedicate 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, we can know if we can get this support [the] the climate is changing and affecting us now and we need to do something about it now – if we bring people on board, I think we can change things. “