Hundreds of northern lakes will permanently lose their ice cover

A shocking number of lakes in the Northern Hemisphere may soon lose their ice cover for good, according to a study from York University. The experts report that at the current rate of greenhouse gas emissions, about 5,700 lakes could permanently lose their ice by the end of this century, and 179 of them will become ice-free within the next decade.

The affected areas include large bays in some of the deepest of the Great Lakes, such as Lake Superior and Lake Michigan. These regions could lose their ice by 2055, unless urgent action is taken to slow global warming.

Many of the lakes that are predicted to stop freezing serve as important sources of drinking water for nearby communities. Losing ice will impact the quantity and quality of the water.

“We need ice on lakes to curtail and minimize evaporation rates in the winter,” said study lead author Professor Sapna Sharma. “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.”

The analysis was focused on 51,000 lakes in the Northern Hemisphere.  The researchers combined annual winter temperature projections from 2020 to 2098 with 12 climate change scenarios to determine which lakes will become ice-free.

“With increased greenhouse gas emissions, we expect greater increases in winter air temperatures, which are expected to increase much more than summer temperatures in the Northern Hemisphere,” said study co-author Alessandro Filazzola. “It’s this warming of a couple of degrees, as result of carbon emissions, that will cause the loss of lake ice into the future.”

The lakes that have the greatest risk of losing ice cover are those in southern and coastal regions of the Northern Hemisphere, and some of them rank among the largest lakes in the world.

“It is quite dramatic for some of these lakes, that froze often, but within a few decades they stop freezing indefinitely,” says Filazzola. “It’s pretty shocking to imagine a lake that would normally freeze no longer doing so.”

The study showed that when the air temperature was above -0.9 C, most lakes no longer froze. 

“Ice cover is also important for maintaining the quality of our freshwater,” said Professor Sharma. “In years where there isn’t ice cover or when the ice melts earlier, there have been observations that water temperatures are warmer in the summer, there are increased rates of primary production, plant growth, as well as an increased presence of algal blooms, some of which may be toxic.”

According to Professor Sharma, more aggressive measures to mitigate greenhouse gas emissions are urgently needed to preserve lake ice cover. “I was surprised at how quickly we may see this transition to permanent loss of ice cover in lakes that had previously frozen near consistently for centuries.”

The study is published in the journal Geophysical Research Letters.

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By Chrissy Sexton, Earth.com Staff Writer