From: The Associated Press
Published March 24, 2009 10:10 AM

Scientists: Less ice on Great Lakes during winter

CLEVELAND (AP) — Ice cover on the Great Lakes has declined more than 30 percent since the 1970s, leaving the world's largest system of freshwater lakes open to evaporation and lower water levels, according to scientists associated with the National Oceanic and Atmospheric Administration.

They're concerned about how the milder winter freeze may affect the environment. But they're also trying to come to terms with a contradiction — the same climate factors that might keep lake ice from freezing might make freezing more likely if lake levels drop due to evaporation.

Scientists at the Great Lakes Environmental Research Laboratory in Ann Arbor, Mich., say global climate change can be at odds with regional climate patterns. Accurately measuring ice cover across a lake system that spans 94,000 square miles in two countries is no small task, they say.

Their studies show that although the amount of ice cover can vary substantially from year to year, the overall coverage on the world's largest system of freshwater lakes is diminishing, especially in the deepest, middle portions of Erie, Huron, Michigan, Ontario and Superior.

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"The deeper the water, the greater the heat storage from summer, and it freezes later than the shallow areas," research Ray Assel told The Plain Dealer. "Now, increase the air temperature and the lake takes in more heat and stores it longer, to the point that many of the midlake areas are freezing over less."

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