Saturday, July 31, 2010

Summer Heat ... in Lake Superior?

"They're swimming in Superior," read part of a headline in the Detroit Free Press this morning. The item, written by Patrick Condon of Associated Press, reported some news I'd heard already from local friends: Lake Superior is hot this summer -- relatively speaking, of course.

Except in late July and August -- and in the past, sometimes even then -- swimming in Superior generally has required wearing a wetsuit. In summer, it is "normal" for lake temperatures to "warm up" to 60 degrees Fahrenheit, but this year, weather buoy readings have reached as high as 71 -- only one degree shy of the record. And we're still a month ahead of summer's peak heat.

Comments on Superior's current warmth have become as prevalent in local conversation as last winter's comments about the lake's lack of ice cover. There is, of course, a relationship between the two, as lack of ice allows lake waters to absorb more heat. Jay Austin of University of Minnesota at Duluth, quoted in this morning's report, explained some interesting nuances of this ice cover/lake heat relationship for Keweenaw Now a few years ago.

The warmth might feel good for swimmers, but it has worrisome ramifications for wildlife and for business. It is consistent with global warming trends, could promote the growth of invasive species, and might lead to greater evaporation which in turn could lower lake levels. And the effects might not stop there.

"Scientists and fisheries managers are concerned," wrote Patrick Condon in the Associated Press report. So enjoy your swim -- but be prepared for more changes in and around Lake Superior, and all the Great Lakes.