Watch the Great Lakes Freeze Over

Watch the Great Lakes Freeze OverYou can measure a winter in many ways: temperature records, snow cover, even travel delays. But to truly see how frigid this winter has been—at least for the eastern half of the U.S.—you need to go way up. Satellite imagery shows that an incredible 88% of the Great Lakes—Superior, Michigan, Huron, Ontario and Erie—are now frozen over. That’s the largest ice cover the Great Lakes have experienced since 1994, and it means that there is an astounding 82,940 sq. miles (214,814 sq. km) of ice covering the biggest collection of fresh water in the world.

How unusual is this? Since 1973, the average maximum ice cover extent for the Great Lakes has been just 50%, and in those four decades, the ice extent has surpassed 80% just five times. (In 2002, just 9.5% of the Great Lakes froze over during the winter, the lowest extent on record, while the greatest extent was 94.7% in 1979.) And no lake is as iced over as Superior, where the extent is 95.3%.

The unusually large extent of ice is due to a logical factor: it’s been really, really cold around the Great Lakes. In the Midwest this January, temperatures averaged 5 to 10 F (3 to 6 C) below the 20th century average. But the endless snowfall around the Great Lakes region—Chicago, which borders Lake Michigan, experienced its third-snowiest January on record, and Detroit had its snowiest month ever—played a role as well, insulating the ice cover when temperatures would rise. If you’re wondering why Lake Ontario has such a smaller amount of its surface covered in ice, that’s because the lake is unusually deep, which gives it a tremendous heat storage capacity. Continue reading….
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