Lake Michigan Is Getting Too Hot and the Cracks Are Starting To Show

February 5 saw 25 people rescued from ice floes on Lake Michigan, a sure sign that the lake's water temperature is rising. The U.S. Coast Guard reported that 11 people who became stranded on an ice floe in Green Bay, Wisconsin, were rescued. Later that same day, the U.S. Coast Guard from Station Saginaw River in Michigan rescued 14 people who were also stranded. All those rescued survived, but two are receiving treatment for hypothermia. The lake is the second largest in the U.S. In winter, the lake would typically be covered in thick ice. But this year, it is a lot warmer than usual.

At the end of January, Lake Michigan only had around 8 percent ice cover. The average amount of ice cover in the lake is usually around 20 percent. This is a historically low level of ice cover. As the weather warms, ice becomes weaker and more unpredictable. The U.S. Coast Guard has warned people to check conditions before going on or near the ice. Timothy Holt, chief of Incident Management for the Coast Guard's Ninth District, told NBC: "The two large ice rescue cases highlight the unpredictability of the ice on the Great Lakes, especially with fluctuating temperatures. We appreciate the swift response from all agencies involved and recovering everyone safely." Lake Michigan's water temperatures have been warming for years. Its water surface temperatures could be warming as much as a third to a fourth of a degree Celsius per decade, a 2021 report from the National Oceanic and Atmospheric Administration (NOAA) said. It is estimated to be warming even more quickly in deeper water, by .06 C per decade. It is just one of the Great Lakes experiencing warming temperatures. All of the Great Lakes—Superior, Michigan, Huron, Erie and Ontario—have been warming for the past several decades. Scientists put this mainly down to climate change. Sarah Marquardt, a senior service hydrologist and meteorologist at the National Weather Service in Milwaukee, told Newsweek: "Temperature and precipitation has been increasing in the Great Lakes basin over the past 70 years, although there is substantial variability year to year." "In general the Great Lakes moderate air temperature near the lakeshore. High temperatures can be slightly cooler in the spring and summer when the lake temperature is colder than the air temperature, and low temperatures can be warmer in the fall and winter when the lake temperature is warmer than the air temperature," Marquardt said. "Warm air temperatures can warm the water temperature, and mild temperatures so far this winter have contributed to Lake Michigan being warmer than average and less ice cover than average. Warmer Lake Michigan water temperatures can keep the air temperature along the lakeshore slightly warmer, compared to inland areas."

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Marquardt said this is usually "most pronounced" during the fall when the air temperature cools below the lake water temperature. "But [this] can also occur any time of year when the water temperature is warmer than the air temperature and winds are light." The temperature in the northern portions of the Great Lakes has been warming by 1.5 F when compared to averages seen from 1901 to 1960, the U.S. Climate Resilience Toolkit reported. The Great Lakes in total, have lost over 70 percent of ice cover over the past five decades, a 2012 study published in the American Meteorological Society reported. The warming conditions are creating a multitude of threats within these lakes, including harmful algae blooms, which can be toxic to the surrounding ecosystem. Warmer temperatures in deep waters can also slow down oxygen processes. This will mean it is unable to support life, killing fish and other animals living in the environment. Lake Superior, which is the coldest lake out of them all, is also warming at an alarming rate. Between 1979 and 2006, Superior's water temperatures increased by 2.5 C, a 2007 study found. The lack of ice on Lake Michigan can lead to a "greater change of lake effect snow" Marquardt said. Lake effect snow happens when cold air moves over warmer lake water. The lower level of air—which is warmed by the lake water—raises water vapor into the atmosphere. But Marquardt said there are also other factors involved. "Lake effect snow is created by evaporation when colder air moves over warmer water and adds additional moisture to the atmosphere. In addition, the wind direction needs to be coming from the direction of the lake, so the moisture can be picked up and transported to the land areas downstream. "So, ice cover along the lake shore limits the extent to which any lake effect snow showers can move inland and limits the availability of water to evaporate into the atmosphere to contribute to snow." Do you have a tip on a science story that Newsweek should be covering? Do you have a question about Lake Michigan? Let us know via science@newsweek.com.