Lake Superior less than 20 per cent frozen

Science is confirming what people living along the shores of Lake Superior have no doubt already guessed: it's been another "very mild ice year," on the Great Lakes.

Large fluctuations in Great Lakes ice cover more common since 1998, says scientist

A graphic from the Great Lakes Environmental Research Laboratory shows that the Great Lakes are largely ice free in March. (Great Lakes Environmental Research Laboratory)

Science is confirming what people living along the shores of Lake Superior have no doubt already guessed: it's been another "very mild ice year," on the Great Lakes. 

"It's actually as mild, if not more mild an ice year than last year," said George Leshkevich, a research physical scientist at the Great Lakes Environmental Research Laboratory in Ann Arbor, Mich. 

On Lake Superior ice cover reached a peak of about 18 per cent on March 4, he said. The ice cover then dipped to 8 per cent, and was back up to about 16 per cent this week. 

The ice is "basically confined to bays and harbours," said Leshkevich. "A little bit along shorelines; but that's it."

It's expected to make easy work for the U.S. coast guard as it begins clearing ice along the route from Duluth, Minn. to Thunder Bay, Ont. on Thursday, in preparation for the shipping season. 

Late 90s a 'tipping point' for ice cover

The lack of ice on the Great Lakes this year stands in stark contrast to 2014, when Lake Superior froze over almost entirely. 

Over the past few decades, Leshkevich said scientists have observed greater fluctuations between very low, and very high ice cover years. 

"It's been an interesting pattern since 1998," he said, "that seems to be the tipping point where, since that time, it seems like winters have been milder, certainly in terms of ice cover — but there have been large fluctuations between severe and mild [ice cover]."

A low ice cover year can lead to greater evaporation from the Great Lakes, and lower lake levels in the summer, he said.