CHICAGO — Ice coverage may be nearing its peak throughout the Great Lakes in a season that has trended closer to average than originally forecast, as Lake Michigan’s water levels are expected to continue their decline well below the string of monthly record highs reached a few years ago.
Lake Michigan’s ice cover hit 37% last week, the most yet in the season, according to data from the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory, which records and models ice coverage.
Ice cover increased in the new year as chilly temperatures froze the Great Lakes region. In recent days, the lakes have been about a quarter to more than 40% covered, sticking close to the long-term average for early February, according to data going back to 1973.
Lake Superior’s coverage has largely been below average, while Lake Erie has seen almost full surface coverage.
In Lake Michigan, ice has appeared in the form of pancakes, balls and, in some northern fishing locations, chunks more than a foot thick. February coverage has been as low as 13% and recently expanded to more than a third of the surface.
“We’re still trending right around that average line,” said James Kessler, physical scientist with NOAA’s Great Lakes Environmental Research Lab. “There’s still some time to reach higher ice cover.”
But whether ice or open water, forecasters continue to urge caution near the lakefront, where a man recently walked out on to the lake without realizing he was on ice.
The last experimental forecast from NOAA’s Great Lakes Environmental Research Lab, updated throughout the season, projected overall coverage close to 49% across the Great Lakes. That was a jump from previous estimates of near-record low coverage after accounting for freezing temperatures and shifts in large-scale climate patterns. In recent days, coverage has reached nearly 50%. The long-term average annual maximum ice cover is about 54%; maximum coverage usually arrives beyond mid-February.
Ice cover is highly variable. Lake Michigan has had as much as 93% of its surface covered, in 2014, while in 2002 coverage hit a low of 12%. But as human action, largely the burning of fossil fuels, drives climbing temperatures, there are now fewer days with ice cover and coverage is decreasing at a rate of about 5% per decade. Lake Michigan’s decline is less severe, while Lake Superior — among the fastest-warming lakes on the planet — has seen the fastest loss.
Less coverage can assist in commercial shipping. It can also fuel lake-effect snow and pose challenges to fish spawning, winter recreation and eroding shorelines already vulnerable to storms.
But one thing crumbling coasts likely won’t have to contend with in the coming months is the monthly record high water levels Lake Michigan reached just a few years ago.
Lake Michigan is projected to continue its drop from those highs, moving closer to the historical average since 1918, ahead of its seasonal rise, according to the latest six-month forecast from the U.S. Army Corps of Engineers.
The monthly mean for Lake Michigan, measured together with Lake Huron, was about 11 inches above the long-term average, but 26 inches below the monthly record high set in January 2020.
“We’re still above average, but we’re lower than the record high and we’re still tracking lower than last year,” said Deanna Apps, a physical scientist with the Army Corps of Engineers.
Evaporation, along with precipitation and runoff, is a major driver in fluctuating lake levels. Ice coverage, with the ability to block evaporation, comes into play in winter.
The first half of 2021 was fairly dry across the Great Lakes region, with more variability in the second half, Apps said. The dry start to the year for the region, combined with cold temperatures and relatively warm waters, led to significant evaporation.
From December to January, Lake Michigan declined about 4 inches. The Lake Michigan and Huron basin received less than an inch of precipitation in January, according to the Army Corps’ report, well below average.
“With changing weather conditions, water levels can rise and fall, and it’s best to be prepared for both high and low water,” Apps said, “even though high water’s on all of our minds with the recent high water.”
In 2020, as lakefront flooding and erosion became commonplace, Lake Michigan remained exceptionally high in winter and ended up breaking the the monthly record for January. That high followed a record low set in January 2013.
Scientists are studying how the swings between extremes may become more pronounced and happen faster in the face of climate change.
Lake Michigan’s drop from near-record highs toward average levels has been noticeable, but what’s happening in Lake Superior especially stands out, said Drew Gronewold, hydrologist and associate professor at the University of Michigan.
Lake Superior has seen a significant drop, with January’s mean about 3 inches below the long-term average and a foot below last year’s level, approaching lows seen about a decade ago. In 2020, the lake set monthly record highs in January and February.
“I’m definitely looking at this as part of this swing in patterns,” Gronewold said.
Scientists will be keeping an eye on the next seasonal cycle to see if the decline continues. Or if, as Gronewold said, “We get a bunch of precipitation six or 12 months from now and it becomes a blip.”
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