Upper Mississippi River freezes over less than ever, another sign life is changing

KELLOGG, Minn. — Standing on the frozen Mississippi River, his back to a few fishers in the distance, Rob Burdis begins to drill a hole into the ice near his feet.

Once the drill stops, the only sound is the occasional crack and pop of the ice as it shifts, about a foot and a half thick under him by his measurement.

On this part of the river, the ice is clear and smooth. Nearer to the Wisconsin side, it's bumpier, shoved together during its formation by the river's powerful current.

It's a good year for ice.

"You kind of start calling them 'good years' now," Burdis said — because, increasingly, they aren't.

Burdis, a water quality specialist with the Minnesota Department of Natural Resources, and Kathi Jo Jankowski, a research ecologist with the U.S. Geological Survey, are among the scientists studying how climate change will impact ice cover and thickness on the upper Mississippi. Three decades of data suggest the ice is already thinner, covers less of the river, and melts earlier than it used to.

By the end of the century, one climate model suggests, the river may only reliably freeze near the Twin Cities — dramatically altering a way of life for the people and animals that use it farther downstream.

Ice duration on the upper Mississippi is shrinking

On the upper Mississippi, which stretches from the river's headwaters in northern Minnesota to Cairo, Illinois, south of St. Louis, the calmer, shallower offshoots of the river known as the backwaters have historically frozen every year in Minnesota, Wisconsin and Iowa. Even the main channel, with its stronger current, can freeze over entirely in particularly cold years.

But research shows that across the globe, rivers that freeze are freezing later and melting earlier, and that includes the Mississippi.

Its longest record of ice cover comes from Lake Pepin, a reservoir of the river that stretches 21 miles between Reads Landing and Red Wing, Minnesota. Records from Lake Pepin dating back to 1850 show that ice thaws about 17 days sooner today than it did then.

Recommended Reading

This winter was the warmest on record for Cedar Rapids

The data that Burdis and Jankowski are looking at is much newer, dating back about 30 years, but it shows a similar trend. Midwinter ice depth has decreased across the sites they monitor, and ice cover area has declined near St. Louis and on the Illinois River, which also is part of the upper Mississippi River system.

Last winter proved to be an extreme example of that trend, with scientists estimating less than one month of safe ice on the river. In January 2024, when Burdis and his colleagues visited their monitoring stations on the river, they traveled in a regular boat instead of an airboat — which skates over the ice — because there was still so much open water. The U.S. Army Corps of Engineers canceled their annual ice surveys of Lake Pepin for the first time in history because there wasn't enough ice to measure.

  Buy Photo

Although this winter appears more in line with what people in the upper Midwest expect, Jankowski cautioned against using it as proof that nothing's changing.

"In your lifetime, you think about what is 'normal,'" she said. "But we're living into an abnormal period."

Between 1831 and 1938, the river froze over at least 10 times as far downstream as St. Louis. Jankowski and her colleagues' data shows that if a concerted effort is not made to reduce greenhouse gas emissions, the main driver of human-caused climate change, the river may only freeze over near Minneapolis by 2100.

Climate change is certainly a factor, but there's more for researchers to learn about what's happening to ice on the upper Mississippi. Scientists want to better understand how quickly ice cover on the river is changing, which spots are experiencing the most loss and whether the river's locks and dams play a role. A 2020 study that examined changes in river ice across the globe noted that on rivers that have been heavily engineered by humans — like the Mississippi — that engineering can alter how ice forms.

Lost ice has consequences for river ecology, safety

Thinner ice that melts earlier has consequences. The most significant is to human safety.

People who regularly use the frozen river to ice fish or do other winter activities likely have favorite spots they visit each year, Jankowski said. But with the increasing instability of the ice, the places they used to be able to count on to be safe may not always be in the future. A 2020 study found that winter drownings in places that are ice-covered increased exponentially during warmer winters, particularly later in the season when the ice is weakest. That indicates a growing hazard for humans as winters warm, its authors noted.

Safety aside, it also will impact recreation that relies on an ice-covered river, like ice fishing. The conditions last winter basically "eliminated" people's chances to do that, Burdis said.

  Buy Photo

The types of fish that can handle winters on the upper Mississippi also could change, Jankowski said. Less ice cover will mean the water will be warmer, and it will flow faster, which is harder for fish. Thinner ice also allows more sunlight to reach the water, meaning algae blooms could proliferate even in the winter. Jankowski and her colleagues have indeed found that warming winters on the upper Mississippi have produced more algae.

Differences in ice cover may also affect the resting spots of migratory birds that make their way along the Mississippi each year.

Not everyone may view these changes negatively. Companies that use the river for shipping goods may be able to start transporting them earlier in the winter if ice breaks up sooner, Jankowski said. Ice on Lake Pepin is the last major barrier that prevents tows from pushing barges further upriver each season.

  Buy Photo

This story is a product of the Mississippi River Basin Ag & Water Desk, an independent reporting network based at the University of Missouri.