Lake Erie had 95% ice cover this winter. What it means for the environment

CBC

25-02-2025

As southwestern Ontario continues to thaw with milder temperatures, it's hard to believe just last week we were at the tail end of a lengthy cold snap.
So much so that Lake Erie reached its winter peak for this season for ice coverage.
Roughly 95 per cent of the lake was covered in ice on Feb. 18, according to satellite data released by the National Oceanic and Atmospheric Administration (NOAA). It's receded a bit since then as the weather has warmed up.
Overall, that's a stark contrast from this time last year when only 36 per cent of the lake was iced over.
The historical average for Lake Erie ice coverage in February is at 60 per cent.
Lake Erie last completely froze over in 1996. It's the shallowest of the Great Lakes meaning it loses heat faster than the others. More recently, scientists say Lake Erie came close to icing entirely over in 2014 and 2015 during bitterly cold temperatures.
At its thickest, the ice was between 15 to 30 centimetres on the lake earlier this month, according to the U.S. national weather service.
Canadian environmental scientist Mike McKay focuses his studies on the Great Lakes.
He says what we've seen the past few months is more of a "typical winter" for this region over the last 50 years.
"Now, these past five years have been a little unprecedented in the frequency of what I call mild winters, low ice years," said McKay.
Benefits for coastal communities
McKay says the pros of having lots of lake ice far outweigh the cons relating to the environment.
For coastal communities, he says, ice cover protects against erosion.
"If you drive along the Ontario shoreline of Lake Erie, you see evidence of receding bluffs, and that's because those bluffs are being battered by winter waves. When we have ice cover, it protects the shoreline against erosion."
It's the same for lake effect snow. McKay says ice protects against westerly winds that predominate across latitudes sweeping over the lake, accumulating moisture and dumping heavy snowfall in places such as Buffalo and Cleveland.
"When we have ice cover, we have much less lake effect snow."
Water's health and level
When there's no ice cover, McKay says more particulate nutrients that are present in the water in the fall stay suspended and available for the following summer.
"They may be used by by algae, for example, and create some of the algae blooms on Lake Erie," he said.
Whereas when there is ice cover it allows the nutrients time to consolidate into the sediment.
Raj Bejankiwar is a scientist with the International Joint Commission's Great Lakes regional office.
A good portion of his work involves algal blooms on the lake, primarily the western basin.
"Less ice, means the water temperature would be warmer," he said. "The sunlight goes all the way to the sediment and that has a negative impact on the spring and summer blooms. It encourages algae blooms. So lesser cover is not good for the lake in terms of algae blooms."
Benjankiwar says there are three main factors for algal blooms to grow and spread on a watercourse, and Lake Erie, unfortunately, ticks all of the boxes.
"One is warm water. The second is nutrients — phosphorus and nitrogen. The third is run off. The lake is shallow so it has all those factors, and that's why algae likes it.
Water levels could also be impacted by large amounts of winter ice.
According to Benjankiwar, the lake loses less water in the winter with more ice build on near the surface.
"That has a significant impact on the water levels … going forward. The evaporation happens more in winter because the temperature of water and air there is a big difference. And because of that ice is the cover is the first defence."
Frozen downside
A main downside for expansive ice formation on Lake Erie, and all of the Great Lakes, is its ability to impede shipping, according to McKay.
"When there's less ice in the lakes, we don't need the effort of the coast guards as much to escort ships. But right now it's been slow going for a lot of the merchant marine."
He says winter ecology can also be impacted when there's too much ice on the lake and researchers can't easily get out on the water to collect samples.