Warmer water in Lake Michigan could mean more snow for surrounding cities

A newly released study suggests water temperatures are warming beneath the surface of Lake Michigan, and AccuWeather meteorologists warn that the rising temperatures of the lake water could actually mean surrounding cities will have more snow than usual.

According to a study by the National Oceanic and Atmospheric Administration (NOAA) published last month in Nature Communications, the water at the deepest points of Lake Michigan is warmer, which is a result of higher-than-usual air temperatures.

AccuWeather National Reporter Emmy Victor explored the impacts in a recent report on the AccuWeather TV network, and they include the potential for more winter storms for Chicago and other cities that surround the lake.

Scientists relied on 30 years of data, covering the period from 1990 through 2020, gathered by long thermometers that were placed in Lake Michigan, the second-largest of the Great Lakes and the fourth-largest lake on Earth. Every hour, water temperatures were recorded from the bottom of the lake to the surface.

AccuWeather Lead Long-Range Meteorologist Paul Pastelok said there may be one key factor that could behind the uptick in lake temperature over the last couple of years in particular.

“Lake water levels over the past two to three years have been running well above normal," Pastelok explained. "It takes a long time to cool down the below-normal surface water with a higher volume of water."

Pastelok said this could be a reason for the warming of water deep down.

Last summer, Lake Michigan was 10 degrees above normal, which resulted in the water taking longer to cool down in the winter. At the start of the year, only 3% of the Great Lakes were covered in ice.

The lack of ice does more than hurt popular recreational activities like ice fishing on the lakes. It can wreak havoc on ecosystems.

“Ice can provide shelter for fish when they’re looking for food and breeding grounds," president and CEO of Alliance for the Great Lakes Joel Brammeier told Victor, adding that other environmental issues can arise as well. "Ice can also protect the shoreline from erosion during the winter," he said.

Brammeier, who reviewed the study but was not involved in it, explained that warmer water means more moisture can rise into the air making for an increase in lake-effect snow. It can also have impacts on the region’s water and food supply.

“If the water remains warm below, this allows nutrients to remain plentiful. If we are dealing with warmer water for an extended period of time, with less wind motion across the lake, then algae will be able to develop,” Pastelok said. He noted that algae blooms may not only occur more frequently under these conditions but also with wider coverage.

When there are large algae blooms in the Great Lakes, Brammeier said that can make drinking water toxic.

"Warmer water makes algae blooms happen more frequently, so it can actually make drinking water quality worse. It provides more habitat for invasive species, fish and wildlife that we don’t actually want in the Great Lakes,” Brammeier said.

Brammeier said the addition of more infrastructure that can prevent pollution and keep unwelcome species out is one way to protect Lake Michigan.

“We’ve got to get real that we’re seeing more severe storms in the Great Lakes. We’re seeing erosion and changing water temperatures," Brammeier said. "There are ways that we can adapt to that so that the Great Lakes and the communities around them stay healthy."

According to AccuWeather Senior Meteorologist Brett Anderson, warmer waters in the Great Lakes could potentially create intense lake-effect snow bands during future winters due to the difference between the lake water temperature and the air. That difference can lead to greater instability and heavier rates of snowfall within snow bands that develop. 

And AccuWeather forecasters say the weather effects of warmer lake waters won't be limited to the winter months with implications on heavier lake-effect snowfalls. The spring and summer months can see their share of impacts, too.

“Warming water would mean weaker, cooling breezes during the summer months” coming off the lake, Anderson said. Less fog would also be anticipated along the shore during the warmer months.

Anderson went on to say that the elevated lake temperature could have an impact on thunderstorms during the warm months. "The warmer lake temperatures may reduce the stabilizing influence of the lake on storms," he said, explaining that "when thunderstorms normally cross the cooler Great Lakes they can briefly weaken as the air is more stable right above the lake."

If the lakes are trending warmer, Anderson explained, then the weakening influence of the lake may become less effective and the storms may stay stronger as they cross over Lake Michigan. 

When asked whether that phenomenon could result in more frequent or extreme thunderstorms, Anderson responded, "Yes, thunderstorms may have a potential to be more severe crossing over the lakes."

Anderson also noted that wind speeds around Lake Michigan have increased over the years, which combined with higher water levels along the lakes may increase the risk for flooding along lakeshores.

According to Pastelok, it takes more than just warm water to create a higher-than-normal frequency of severe weather, but the warmer water doesn’t hurt.

“I think that is the bigger thing. Cooler water creates cooler air just above the surface. This air can be less buoyant or stable. With cooler water and more stability, there is a tendency to weaken thunderstorm complexes moving across the lakes,” Pastelok said.

Additional reporting by AccuWeather National Reporter Emmy Victor.

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