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Lessons in sailing, science
Superior Telegram (8/16)
A workshop offered by the Great Lakes Sea Grant Network has local educators on a six-day boat trip as part of the Duluth Tall Ships Festival.

NOAA to work with MTU scientists out on Lake Superior
WLUC-TV - Marquette, MI (8/16)
With the help of The National Oceanic Atmospheric Administration or NOAA, Michigan Technological University scientists continue to learn about their surroundings.

Sturgeon hatchery to offer tours in Onaway
WPBN-TV - Traverse City, MI (8/10)
The Michigan Department of Natural Resources is offering tours of the Black River sturgeon hatchery in Onaway. During the free tours, researchers will be available to talk about sturgeon biology, reproductive ecology and this year’s research.

Watch 4 months under Lake Michigan pass by in just 3 minutes
MLive (7/29)
Ever wonder what goes on underneath the surface of Lake Michigan? If so, you're not alone. Scientists wonder, too.

TEACH Calendar of Events
What's going on in your neighborhood this month? Meet other people and learn together at recreational and educational events! Our new dynamic calendar is updated daily with current educational events.
TEACH Questions & Answers

Do the Great Lakes freeze in the winter?
from Debbie in Olyphant, Penn., Michael in Kenosha, Wisc., and Jim in St. Clair Shores, Mich.

The Great Lakes do freeze, but not completely. According to Ray Assel of the Great Lakes Environmental Research Laboratory, ice cover on the Great Lakes varies from lake to lake and year to year. For example, in a year with normal temperatures, 25 percent of Lake Ontario will be frozen over, while up to 90 percent of Lake Erie will be frozen. However, wind and water movement over bodies of water as large and deep as the Great Lakes make it unlikely the lakes have ever frozen over completely for any significant length of time.

The Great Lakes have come close to freezing over completely during the extremely cold winters of 1976-77, 1977-78 and 1978-79, with up to 90 percent ice coverage. However, Assel says that severe winter air temperatures are not necessary for large ice cover on the lakes. A cool summer and fall can result in below normal water temperatures by late fall. Extensive ice cover can then form with only average winter temperatures.

Old Ice bridge As for the Niagara Falls, the volume and speed of the water flowing over the falls prevents them from freezing, as does the ice-boom at the mouth of Lake Erie. The ice-boom is a series of floating steel pontoons extending across the river from Buffalo, New York to Fort Erie, Ontario. It prevents ice from clogging the river and hydroelectric intakes by helping an "ice bridge" (a stable ice cover) to form at the mouth of Lake Erie. Before the installation of the ice-boom in 1964, the American side of the falls froze over in 1909, 1938 and 1949 because ice jams upstream reduced the water flow. Ice bridges can also form below the falls when ice goes over the falls and freezes to the edges of the gorge, resulting in a buildup of ice (as thick as fifty feet in some places) stretching across the entire river. For photographs of historical ice bridges on the falls, go to Edsen Breyer's Postcard Museum.

For a look at current and historical Great Lakes surface and ice cover, go to GLERL's Great Lakes Surface Environmental Analysis pages.

Thank you for your questions!

References
Nilsson, Matt. Not Easy to Freeze. Earthwatch Radio, 1/25/00.
Niagara Falls, Thunder Alley.


Answered on January 8, 2001

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