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Warmer winters are affecting water levels, Great Lakes ecosystems

St. Mary's river ice chunks during the 2018 winter.
Joe Kirklin
St. Mary's River ice chunks during the 2018 winter.

Michigan's winters are getting warmer and shorter, according to the National Oceanic and Atmospheric Administration (NOAA). These trends can have consequences for Great Lakes ecosystems.

In the last 50 years, researchers have noticed a 5% decrease in ice cover per decade. Average surface water temperatures have also significantly gone up — with Lake Superior summer surface temperatures increasing by 4.5 F between 1979 to 2006.

Don Uzarski is the director of Central Michigan University's Institute for Great Lakes Research (IGLR). He said low ice cover results in more evaporation, causing lake levels to drop and precipitation to increase. 

Uzarski said our response to changing lake levels can exacerbate environmental issues. When levels drop, he said, dredging can erode shorelines and release toxins buried in sediment.

On the flipside, when water levels increase, Uzarski said building seawalls and destruction of shoreline vegetation may increase.

"We try to fight the water levels and when we do that, we have a negative impact on the ecosystem, that impacts everything all the way to the fish," Uzarski said.

According to Michigan Sea Grant, water levels on the Great Lakes "have always been highly variable" due to various seasonal factors, and scientists are still studying how climate change will affect lake levels.

Uzarski said warm water temperatures can directly hurt species like whitefish and trout, and harm coastal wetlands, where many fish spawn, grow and feed.

"The coastal wetlands of the Great Lakes are critical areas for productivity for fish [and wetlands] are affected by lake levels and temperatures," Uzarski said. "... and the sensitive cold-water species are having a much harder time utilizing these regions."

At the end of 2023, the U.S. Army Corps of Engineers predicted that water levels on Lake Michigan and Huronwill be one to six inches lower, compared to the previous year.

For more information about climate trends and impacts on the Great Lakes, visit the NOAA GLISA page.

Teresa Homsi is an environmental reporter and Report for America Corps Member based in northern Michigan for WCMU. She covers rural environmental issues, focused on contamination, conservation, and climate change.
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