Freshwater lake ice cover faces fragile future: study

·2 min read

Canadian researchers are concerned about the impact climate change will have on drinking water quality, as warmer temperatures lead to less ice cover on lakes.

The paper, published in Geophysical Research Letters, was led by York University science Prof. Sapna Sharma. The research found, across the northern hemisphere, by 2100, 5,700 lakes are likely to stop freezing during the winter. Of those, 179 lakes will lose ice cover by 2030.

“We need ice on lakes to curtail and minimize evaporation rates in the winter,” Sharma said. “Without ice cover, evaporation rates would increase, and water levels could decline. We would lose freshwater, which we need for drinking and everyday activities. Ice cover is extremely important both ecologically and socio-economically.”

While water freezes after temperatures reach 0 C, it must be colder still for lakes to have ice cover. The researchers found air temperature needed to be below -0.9 C for most lakes to freeze. The larger or deeper the lake, the colder it needs to be; some need temperatures as low at -4.8 C to freeze.

“It is quite dramatic for some of these lakes, that froze often, but within a few decades they stop freezing indefinitely,” said co-author and postdoctoral fellow Alessandro Filazzola.

“It’s pretty shocking to imagine a lake that would normally freeze no longer doing so.”

Examining the data, Filazzola found no Manitoba lakes on the list of bodies of water expected to stop freezing altogether. Most of the lakes that are expected to remain open year-round are in the southern and coastal regions of the Northern Hemisphere. However, Manitoba lakes will still be affected.

“Large lakes, such as Lake Manitoba, Winnipeg, Winnipegosis, and Cedar will each probably experience an increase in ice-free years in the future. I just have no data to support by how much and by when,” Filazzola said.

The research shows Lake Superior and Lake Michigan could permanently become ice-free by 2055, if nothing is done to curb greenhouse gas emissions, or by 2085 with moderate changes.

Sarah Lawrynuik, Local Journalism Initiative Reporter, Winnipeg Free Press