Climate change has led to warming of lakes at a rapid rate, even faster than the air or the oceans, according to York University researcher Sapna Sharma, professor of biology in the Faculty of Science and the lead author of a new global study.
“We found that lakes are warming at an average of 0.34 degrees Celsius each decade all around the world, threatening freshwater supplies and ecosystems,” Sharma said. “This can have profound effects on drinking water and the habitat of fish and other animals.”
The study predicts that at the current rate, algal blooms, which can ultimately rob water of oxygen, will increase 20 per cent in lakes over the next century. Algal blooms that are toxic to fish and animals would increase by five per cent. These rates also imply that emissions of methane, a greenhouse gas 25 times more powerful than carbon dioxide, will increase four per cent over the next decade.
“We found that ice-covered lakes, including Canadian lakes, are warming twice as fast as air temperatures and the North American Great Lakes are among the fastest warming lakes in the world,” said Sharma.
In total, 236 lakes were monitored annually for the past 25 years. “While that’s a fraction of the world’s lakes, they contain more than half the world’s freshwater supply,” says Sharma.
Said to be the largest study of its kind, it is also the first to combine manual lake measurements — made by thousands of scientists over more than a century — with satellite measurements of lake temperatures collected by NASA over a quarter century.
The study results were announced today at the fall meeting of the American Geophysical Union in San Francisco, attended by some of the more than 60 scientists from across the world who have contributed to this study.
The study, “Rapid and highly variable warming of lake surface waters around the globe,” funded by York, NSERC, NASA and the National Science Foundation, is published in the journal Geophysical Research Letters.
According to Sharma, the study reveals the importance of assessing the impact of climate in global freshwaters, to evaluate the sustainability of global supplies of food and freshwater.