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Ice cover on the Great Lakes hits a 50-year low

A satellite image showing the Great Lakes with very little ice cover.
courtesy of NOAA
NOAA CoastWatch
A satellite image taken February 12th shows how little ice is on the Great Lakes right now.

Ice cover on the Great Lakes has dipped to a 50-year low, according to federal data compiled by the National Oceanic and Atmospheric Association.

Ice levels on the lakes have been below average since late December. Even when a burst of arctic weather helped build up ice cover in early February, coverage remained well-below historic averages. And with warm weather across Michigan earlier this week melting what little ice there was, Great Lakes ice cover is now at a historic low.

On Tuesday, NOAA reported only about seven percent of the lakes had ice cover. Usually at this time of year, that number is closer to 40%. Scientists have shown that there has been a trend of less ice on the Great Lakes since at least the 1980s, but that’s not all that’s going on.

Line chart showing the percentage of Great Lakes surface that's covered in ice at different times of the year. A black line shows this year's percentages, which is well below average and currently at a record low.
A NOAA chart showing average ice cover across the Great Lakes over the past 50 years.

“There are really high fluctuations from [one] year to another,” said Ayumi Fujisaki-Manome, a NOAA research scientist who studies ice on the Great Lakes. “Like if you look at a very recent year, 2019, it was pretty extremely cold. We got a good amount of ice cover in that winter.”

Those yearly fluctuations are not necessarily coincidental, notes the Great Lakes Integrated Sciences and Assessments, or GLISA, a research project at the University of Michigan that’s supported by NOAA.

The variability all comes down to how evaporation affects the surface temperature of the lakes. Less ice in winter means more evaporation, but when water is pulled off the lake surface through evaporation, it makes the surface cooler, which can lead to more ice the following winter, as GLISA notes on its website:

“Warmer water temperatures result in greater evaporation because water molecules are moving faster, making it easier for them to transition from liquid to vapor (or, evaporate). Evaporation removes latent heat from the surface, resulting in a cooling of the surface, and the potential for greater ice cover. For example, if the previous winter experienced low amounts of ice cover (more solar warming), higher evaporation rates (strong cooling effect) during the fall would lead to increased ice cover the next winter. Conversely, cooler water temperatures during fall leads to lower evaporation rates (less cooling) thereby decreased ice cover. Interestingly, an extreme of one setup (i.e., high ice cover one winter) can lead to the opposite extreme (i.e., low ice cover) the next year.”

These fluctuations, Fujisaki-Manome said, can be extreme from year to year, even though the long term trend seen over the past few decades is for less ice cover in winter over time.

Climate change is driving the long-term trend and scientists such as Fujisaki-Manome expect the trend to continue, which could cause dramatic effects on the land near the lakes.

One likely outcome: more dramatic lake-effect snow storms.

“Less cover on the lakes means more open water on the lakes,” Fujisaki-Manome said. “And open water during winter is actually a perfect setup for lake effect snow storms.”

As a cold front moves over the lakes, Fujisaki-Manome said the air tends to pass right over solid ice. But open water is warmer, and can act as a kind of energy source for the air mass.

“The cold air can absorb a lot of moisture and heat,” she said. “And then once it reaches the downwind land surface, it dumps a lot of snow.”

And, if it’s not cold enough for snow, the storm will drop rain, leading to more extreme flooding events across Michigan and other Great Lakes states.

Fujisaki-Manome said less ice can also mean more shoreline erosion because ice can act as a barrier to the high waves brought on during big winter storms. “If you lose ice cover, you lose this protection,” she said. “And that can lead to damage to shoreline or coastal flooding.”

The federal government has stepped up funding for programs meant to better understand, and prepare for how climate-change is affecting life on the lakes. That includes more money for research, and for infrastructure improvements to handle more extreme weather events. Because the changes are coming.

“We are not quite ready to be adapted to such large variations,” said Fujisaki-Manome. “And that is one major thing to think about.”

Dustin Dwyer reports enterprise and long-form stories from Michigan Public’s West Michigan bureau. He was a fellow in the class of 2018 at the Nieman Foundation for Journalism at Harvard. He’s been with Michigan Public since 2004, when he started as an intern in the newsroom.
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