Early ice cover on Lake Superior bucks trends
The trend for nearly 30 years has been less ice cover on the big lake, with water temperatures rising.
A University of Minnesota-Duluth study found the lake's temperature has risen 4.9 degrees since 1979, about twice as fast as the rise in air temperatures in our area.
The Lake Superior water-temperature increase has been cited as one of the most pronounced examples of global warming anywhere on the planet.
Another study of ice-cover data for Lake Superior between Bayfield and Madeline Island by Bayfield's Forrest Howk shows that there are now, on average, 45 fewer ice-covered days each winter than in 1857. Howk found that thick ice coverage has been declining by a full day every three years over the 150-year period.
The trend has been even faster over the past 25 years, with ice declining by one day every year. Computer plots show, if the pattern holds, there will be no days of heavy ice cover between Madeline Island and Bayfield by about 2037.
The National Ice Center in Washington, D.C., tracks how much ice covers the Great Lakes but relies on satellite imagery that has proven sketchy in recent years. Steam rising from open water can be seen as ice, for example. The center has proclaimed Lake Superior frozen over in the past when vast amounts of open water were visible from Duluth, such as in March 2003.
Officially, according to the Great Lakes Aquarium, the lake entirely froze over most recently in 1979 and 1962, but it came very close to 100 percent ice-covered in 1996, 1994 and 1972.