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WeatherTalk: When the lakes freeze over, it's quite a process

One key is the fact that water reaches maximum density at 39 degrees Fahrenheit.

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Area lakes have been reluctant to freeze early this winter due to not enough cold weather. The process of lakes freezing over is as complex as it is fascinating. The Earth under the ice is warm, which creates an interesting calculus problem as cooling rates from cold air do battle with heat rising from below. Adding to the mystery is the fact that water reaches maximum density at 39 degrees Fahrenheit.

Once the surface of the water reaches 39 degrees, it sinks and is replaced by warmer water rising up from below. This process continues until the entire system is colder than 39 degrees and, only then, can the lake begin to freeze. This is part of why shallow lakes freeze much more quickly. Once ice forms, it acts as an insulator, which slows the thickening of the ice. Snow cover on top of the ice is an even better insulator and can greatly restrict ice formation underneath.

John Wheeler is Chief Meteorologist for WDAY, a position he has had since May of 1985. Wheeler grew up in the South, in Louisiana and Alabama, and cites his family's move to the Midwest as important to developing his fascination with weather and climate. Wheeler lived in Wisconsin and Iowa as a teenager. He attended Iowa State University and achieved a B.S. degree in Meteorology in 1984. Wheeler worked about a year at WOI-TV in central Iowa before moving to Fargo and WDAY..
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