Why are there no tides on the Great Lakes?

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Dear Tom,
Why are there no tides on the Great Lakes?
— Irma Horn
Dear Irma,
Even though the Great Lakes are considered to be essentially nontidal, like all bodies of water, they do experience tidal fluctuations caused by the gravitational pull of the sun and moon. However, they are so minute that they are unnoticeable, masked by much greater fluctuations of the lake level produced by wind and air pressure. On Lake Michigan, there are twice-daily tides of 0.5 to 1.5 inches.Dave Schwab, a research scientist at the University of Michigan’s Water Center, does note the existence of a slightly larger Lake Michigan tidal swing in Green Bay, where local geography can generate fluctuations up to four inches. In sharp contrast, this planet’s largest tidal swing occurs in the Bay of Fundy in Nova Scotia, where high and low tide can vary by more than 50 feet.

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