(WXYZ) — Climate change is not only warming the surface of Lake Michigan, but it's also warming the deep waters of the lake, which could have a significant impact on the lake's ecosystem and mixing process.
A long-term study from the National Oceanic and Atmospheric Association, published in Nature Communications, looked at 30 years of nearly hourly water temperature measurements from Lake Michigan spanning the entire water column, from the lake bottom to just below the surface.
The study's lead author, Eric J. Anderson, said the warming of the lake's deepwater has a number of implications.
Lake Michigan is a dimictic lake, which means the water mixes twice a year from the top to bottom, and the warming means the times of mixing are shifting.
"In the study, we not only found that the lake is warming down to below 100 meters deep, but most of that warming is happening in the wintertime," Anderson said. "That really means the winter is getting shorter and less intense."
The lake mixes once in the spring and once in the fall. In between those, the lake will have ice growth in the winter and a warm surface layer developed in the summer.
According to the study, the water has warmed about .11 degrees Fahrenheit each decade. That means less ice cover, which is already declining across the Great Lakes.
It also means that it could shift the way the lake mixes in the future.
"The projection is that Lake Michigan, with current climate trends, will turn into a lake that mixes only once per year within the next century," Anderson said.
What that means, according to Anderson, is that the winter collapses and we don't have the winter as we know it now. That can have a major implication on things living in the lake and disrupt the entire food chain.
"I think the most dramatic implication would be to the food web in the lake and our reliance on that. The fisheries we rely on, also the way we're affected by things like algal blooms and other things that occur in the lakes," Anderson said.
According to Anderson, there could also be effects on the Michigan weather. With slightly warmer lake temperatures, the cold air masses that come from Canada over the Great Lakes will pick up more moisture from the lake and turn that into lake-effect snow.
One thing that's important to remember, according to Anderson, is that lake temperatures respond to what's going on in the atmosphere.
"The lake temperatures have gone up slightly in these deep waters and on the surface," Anderson said. "We're also already experiencing those same drivers, meteorological trends, like warmer air temperatures. This is just one part of that narrative or story that's happening in the region."
According to Anderson, though the data is specific to Lake Michigan, they expect it to represent generally what's happening in large lakes around the world, especially at the same latitude as Lake Michigan.
"We would expect this to be similar to what we'd see in the rest of the Great Lakes, with the exception of Lake Erie because it's so shallow, it's not going to have the same deep-water trends, just because there isn't the deep-water there," he said.
