By Matt Prokopchuk · CBC News · September 11, 2019

A researcher with the University of Minnesota Duluth says climate change is causing Lake Superior to be among the fastest warming lakes in the world and, even with Superior's immense size, it's not immune to environmental changes.

The big lake's average surface temperature in the summer months has risen 2 C over the past 30 years, said Jay Austin, a professor in the university's physics and astronomy department and its Large Lakes Observatory.

"The numbers that we toss around often sound small, you know a few degrees Celsius over the last 30 or 40 years, but they end up having an outsized effect on how the lake works," he said.

"We often think of Lake Superior as this giant immutable thing where it's going to be very insensitive to small changes because it's so large, but in fact, almost exactly the opposite is true."

While Austin said he's not an expert in biology, his biggest concern from an environmental perspective is that a warmer lake would be more hospitable to invasive species. What Austin said he is seeing is changes in how much ice cover lake Superior gets in the winter.

While some years have seen very widespread and thick ice conditions, Austin said that he's seeing "lots of years, certainly a lot more recently, where the lake basically doesn't freeze at all." The difference in average winter air temperature it takes to cause those two extremes, he said, can be as small as between one and two degrees.

Different winter lake conditions, he said, also cause quite large changes in how the lake behaves the following summer.

"Relatively small changes in the climate seem to be leading to large changes in, at least the ice climate of the lake," he said. "That ice ends up playing, or at least is highly correlated with, what goes on throughout the rest of the year."

"When you have one of these years with a lot less ice, you're sort of preconditioning the lake for a warmer year throughout the rest of the year."

Austin is scheduled to be in Thunder Bay for Lakehead University's 2019 climate change symposium on Sept. 23 where he said he will be speaking to how fragile the big lake is even due to, what seem like, small changes.

Blue-green algae research

The Large Lakes Observatory is also studying the presence of blue-green algae blooms reported on Lake Superior's south shore, particularly two large ones — one in 2012 and one in 2018. Last year's bloom stretched all the way from the Twin Ports east to the Apostle Islands, or about 100 kilometres, said Robert Sterner, the observatory's director.

The blooms, also known as Cyanobacteria, "are being recorded in new places all over the world, every year," Sterner said, adding that scientific studies generally look at two main contributors: warming water and an increase in nutrients in the water."
Naturally, we're looking at the same two things here in Lake Superior, which is ordinarily a cold and clear lake environment," he said. "But it is subject to climate warming."

Sterner said his institution's research is still in the early stages but the two bloom years were relatively warm.

"It's either a coincidence or there is, in fact, something behind the possibility of warming contributing to this new incidents of blue-green algae in Lake Superior," he said.

Sterner said it is "highly unlikely" that Superior will see widespread algae cover, like Lake Erie.