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Scientists Wary Of Lake Superior Warming

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  • Mike Neuman
    Scientists Wary Of Lake Superior Warming Associated Press Posted on http://www.todaysthv.com/ on February 28, 2007 For Jay Austin, who has made a career of
    Message 1 of 1 , Mar 2, 2007
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      Scientists Wary Of Lake Superior Warming
      Associated Press
      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
      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.
      http://greatlakesdirectory.org/mn/030107_great_lakes.htm
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