Ice is vanishing earlier than ever from lakes across the northern U.S.

August 25, 2024

Lakes from Minnesota to Maine are usually still frozen over at this time of year, as signs of spring slowly emerge across the country’s northern tier.

Instead, the ice is breaking up or is already gone on many lakes with more than a century of records. So-called ice-out — when waters become navigable for boats again — is happening earlier than ever witnessed.

It’s a vivid sign that winters are warming faster than any other season across what is usually the frigid North. Declining snowfall and ice cover serve as both symptom and driver of that trend, in a feedback loop that is having stark effects in communities that thrive on harsh winters.

“It’s a little bit unsettling,” said Chris O’Brien, a Wisconsin native who now serves as a marketing coordinator for Fresh Water, an environmental nonprofit in the Twin Cities.

During Wisconsin’s annual 16-day sturgeon spearing season on Lake Winnebago in February, the northern half of its waters were free of ice, said Wayne Schumacher, a Fond du Lac resident and spearing enthusiast. And where there was solid ice, sturgeon hunters could only get out on the lake on foot or in ATVs, but not by car or truck, as usual. Their harvest fell well short of annual conservation limits by the season’s end Feb. 25.

And then a few days later, he said, the lake’s ice broke up.

While it’s normal for ice to cover lakes around Wisconsin for 100 days or more each winter, this year, it didn’t stick around for half that long during what residents called a lost winter, or the winter that never was.

“It just seems like we’re not getting the winters that we used to get,” Schumacher said.

Data on the onset of lake ice season is spotty, said Pete Boulay, a climatologist with the Minnesota Department of Natural Resources, because waters often ice over in fits and starts as temperatures fluctuate from fall into winter. But its disappearance is hard to miss, so records are thorough. On many of Minnesota’s thousands of lakes, ice-out records go back to the 1860s or 1870s.

“Ice-out is so dramatic,” Boulay said.

And the data shows that this year’s ice-out is even more dramatic.

“In a normal-ish year, the last week of March is when we start thinking about ice-out,” Boulay said. “We already have hundreds of lakes that are free of ice.”

On Clear Lake, about 45 miles northwest of Minneapolis, ice-out came March 1, about a month earlier than average and the earliest in records that go back to 1874. In the Twin Cities region, the ice-out on Lake Minnetonka came about as early: Instead of a typical April 13 ice-out, it came March 13.

Ice-out arrived March 8, five weeks earlier than usual, on White Bear Lake, just north of St. Paul, the earliest since record-keeping there began in 1928.

The same day, the ice broke up on Lake Osakis, 110 miles northwest of the Twin Cities. It set a record for a lake where ice records go back to 1867. The median ice-out date over those 156 years: April 19, six weeks later.

It is perhaps the clearest sign of what was a record-warm winter across the contiguous United States and for the Northern Hemisphere, according to the National Oceanic and Atmospheric Administration. The warmth was the most dramatic across regions that are typically the coldest, setting records for the mildest winters on record in eight states across the Upper Midwest, Great Lakes and Northeast.

Such a pattern is to be expected during episodes of El Niño, the global climate pattern tied to warmer-than-normal Pacific Ocean waters. Among its domino effects around the world is a tendency toward milder winters for the Upper Midwest.

But the rise in average global temperatures because of human-caused climate change is helping to compound the trend.

There never was much of an ice cover on Lake Winnipesaukee, N.H., this winter, and as dramatic as it was, it only punctuated what feels like a years-long trend, said Pat Tarpey, president of a nonprofit that protects the lake’s health. Ice fishing derbies and pond hockey tournaments that were once common have been canceled or moved to smaller lakes, and more winter precipitation is falling as rain, not just snow, she said.

Lake Winnipesaukee has historically seen ice-outs toward the middle or end of April, but this year, aerial observations revealed its arrival Sunday. It was a day earlier than the previous record-setting ice-out, in 2016. In each of the past four years, ice-out has arrived no later than April 8.

And besides disappearing earlier, the ice has been taking longer to form.

“Ice-out was almost an anticlimax this year because there was barely any ice-in,” said Al Posnack, a volunteer with the Lake Winnipesaukee Sailing Association.

That was the case across the Great Lakes as well. Ice cover did not start spreading across the system until mid-January, and peaked for the season only a few weeks later, covering about 16 percent of the lakes’ surface. In an average year, ice covers about 40 percent of the lakes well into March.

Spring’s earlier arrival may be good news for lakeside residents eager to open up their cabins for the season, or for those whose property may only be accessible by boat, Tarpey said.

But it also brings worries of waters too warm for many marine species, and a thriving environment for toxic algae blooms, she said. Last year, two such blooms prompted health advisories on Lake Winnipesaukee, one of them in late October, much later than normal, she said.

“We’re concerned that in the coming season, we’re going to see a lot more,” Tarpey said.

Though spring has arrived, the cold isn’t gone just yet, however. Snow is forecast across the country’s northern tier in the coming days, from Montana to Maine. It won’t be enough to bring ice cover back to lakes, but it’s at least a reminder of what’s normal in those parts of the country, Posnack said.

“All of a sudden we have a wake-up call that spring never comes this early in New Hampshire,” he said.

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