Ice cover blocks evaporation, the leading cause of low water. It also will keep the lakes cooler for a longer time this year, delaying the onset of heavy evaporation season, scientist John Lenters reported in a paper last month, although the benefit is partially offset by stepped-up evaporation shortly before the ice forms.
In Lake Superior, snowbound Isle Royale National Park is home to a dwindling and inbred wolf population that is usually trapped on the island. Biologists hope a newcomer or two will venture to the park now that the lake is almost entirely frozen over. The park's first wolves are believed to have crossed an ice bridge from Canada, 15 miles away, in the late 1940s.
There's also a chance that one or more of the island's wolves could grab the rare opportunity to escape.
"They are inveterate travelers," veteran wolf expert Rolf Peterson said. "And they don't need a reason that would make sense to us."