Scientists Wary Of Lake Superior Warming
- Scientists Wary Of Lake Superior Warming
Posted on http://www.todaysthv.com/ on February 28, 2007
For Jay Austin, who has made a career of studying the Great Lakes,
the warming climate around Lake Superior is no mystery. But he was
surprised to find the waters of the lake itself warming even more
Austin, a Duluth professor and a researcher with the University of
Minnesota-Duluth's Large Lakes Observatory, has studied decades of
data. What he found was water temperatures rising almost twice as
fast as air temperatures more than 4 degrees for the average
The increase is having dramatic effects.
"The date of what we call the spring overturn has been getting
earlier in the year," Austin said. "It's basically the start of the
summer season in the lake. It's when you start to develop strong
positive stratification: warm water sitting on top of cool water."
In two decades, the spring turnover has moved up two weeks from early
July to mid-June.
Part of that likely is due to a loss of ice cover. Since ice is
reflective, when it's not there it makes it easier for the lake to
In another 35 to 40 years, Austin said, Lake Superior will have very
little ice cover.
While that may sound good to people who swim or sail on the lake,
it's not so good for plants and animals, including the lake's native
"If there's less ice over time, and there appears to be, there's a
chance for greater storminess in the sort of shallow water (bays)
that the whitefish spawn in," said Steve Coleman, who directs the
Large Lakes Observatory.
Bob Sterner, a University of Minnesota biologist, said warming
usually speeds the growth of fish and the plants they feed on. But
when it's too fast, it can create big problems.
"Paradoxically, you may well see the lake essentially becoming even
more desert-like in the sense that you've reduced the flow of
nutrients into the system across that temperature gradient," Sterner
The research will be published soon by the American Geophysical
Union. The Duluth scientists' next project is trying to prove their
suspicion that diminishing ice is contributing to falling lake levels.