Scientists Alarmed at Lake Superior Rapid Warming
Pastor Dale Morgan
Feb 26, 7:19 PM EST
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Scientists Alarmed at Lake Superior Rapid Warming*
DULUTH, Minn. (AP) -- 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 rapidly.
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 surface temperature.
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
absorb heat.
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 whitefish.
"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 said.
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.
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Information from: Minnesota Public Radio News, http://www.mpr.org