The Great Lakes are feeling the heat from climate change.
As the world's largest freshwater system warms, it is poised to systematically alter life for local wildlife and the tribes that depend on it, according to regional experts. And the warming could also provide a glimpse of what is happening on a more global level, they say.
"The Great Lakes in a lot of ways have always been a canary in the coal mine," Cameron Davis, the senior adviser to the U.S. EPA on the Great Lakes, said last week. "Not just for the region or this country, but for the rest of the world."
And it seems the canary's song is growing ever more halting.
Lake Superior, which is the largest, deepest and coldest of the five lakes, is serving as the "canary for the canary," Davis said at a public meeting of the Interagency Climate Change Adaptation Task Force last week, pointing to recent data trends.
Total ice cover on the lake has shrunk by about 20 percent over the past 37 years, he said. Though the change has made for longer, warmer summers, it's a problem because ice is crucial for keeping water from evaporating and it regulates the natural cycles of the Great Lakes.
But the warming shows no sign of abatement. This year, the waters in Lake Superior are on track to reach -- and potentially exceed -- the lake's record-high temperatures of 68 degrees Fahrenheit, which occurred in 1998.
Analysis of several buoys that measure temperatures in the lake reveal that the waters are some 15 degrees warmer than they would normally be at this time of year, Jay Austin, a professor of physics at the University of Minnesota, Duluth's Large Lakes Observatory, said in a recent interview.
His analysis of National Oceanic and Atmospheric Administration data indicates that summer for the lake, which happens at about a 40-degree threshold, came about a month early this year.
A 'tremendously anomalous' year
"This year is just tremendously anomalous," he said. "This year ranks up there with the warmest water we have ever seen, and the warming trend appears to be going on in all of the Great Lakes."
While the warmer waters make for more comfortable swimming conditions for humans, they may also make for more habitable conditions for invasive species in places that have previously been relatively free of such pests.
The jawless parasite attaches itself to the side of trout, bores a hole and sucks the trout's blood, growing to as long as 3 feet in the process, according to Kitchell. But in warmer weather, the lamprey may feed faster, grow bigger and lay more eggs, he said. The creatures will also become adults faster and require more frequent extermination, thanks to the warmer waters, warned Marc Gaden, a spokesman for the Great Lakes Fishery Commission, in an interview.
Meanwhile, the dead trout, with gaping holes in their sides, will sink to the seafloor below -- far from where humans can witness the evidence.
But the full impact of decades of water warming is not bound to the murky depths.
The warming may also threaten practices that are central to the "cultural identity" of indigenous tribes that live in the Great Lakes area and depend on certain weather and water conditions to farm wild rice, according to Nancy Schuldt, the water quality coordinator of the Fond du Lac Band of Chippewa Indians.