Northern lakes losing ice coverage due to climate change, finds study

Some lakes in the northern hemisphere have been warming six times faster in the last 25 years, than at any other time, according to a new study.

A study published in the Journal of Geophysical Research Biogeosciences measured the ice coverage of 60 lakes, and found that climate change has contributed to faster rates of ice loss.

"We were pretty shocked," said Sapna Sharma, an associate professor at York University's department of biology, and one of the study's authors.

Sharma said their findings found an acceleration of the ice loss in northern lakes when compared to studies done at the turn of the century.

They focused on lakes that had at least 100 years of data and measurements related to their ice coverage in the winter. Among them were Lake Nipissing, in northeastern Ontario, and Lake Superior.

"And Lake Superior was the fastest warming lake in our study," Sharma said. "It lost over 60 days of ice cover since 1857."

She said the changes were less drastic for Lake Nipissing, however.

Sharma said when a lake loses ice coverage in the winter it has a number of ecological impacts.

"You can think of ice as a lid on the lake in the winter," she said. "And when you remove that lid, what many studies have shown is that winter evaporation rates increase."

That increased evaporation leads to lower water levels, and less freshwater overall, which can affect organisms in the lake.

Less ice also leads to a longer growing season for organisms like blue-green algae, Sharma said, which can lead to toxic blooms. 

And there are also the impacts on winter activities, which have shorter seasons, and a higher risk of drawing in the winter, due to thin ice. 

Sharma said reducing greenhouse gas emissions would help preserve ice coverage on northern lakes.