Global warming brings earlier spring thaw to Great Lakes
09:45 20 August 2005
NewScientist.com news service
The Great Lakes of the US, the planet's largest concentration of fresh water, is thawing earlier each spring, according to an analysis of ice break-ups dating back to 1846.
Barbara Benson of the University of Wisconsin-Madison, and colleagues studied the timing of ice break-up on 61 lakes in Minnesota, Wisconsin, Michigan, New York and Ontario between 1975 and 2004, during which time the average global air temperature rose by 0.4 °C. The team gathered the dates from government databases, lake associations, newspapers and local residents.
On 56 of the lakes the spring thaw showed an earlier trend, occurring two days sooner each decade on average. Though the thaw has been happening ever earlier since 1846, the calculations show the rate of change is now more than three times as fast as it was before 1975. Benson says the date of ice break-up has "marched northward 100 kilometres per decade" in that time.
"What's happening around us is big enough and so far out of our control that it is affecting the whole Great Lakes region," says team member John Magnuson.
The team presented its findings at the Ecological Society of America's meeting in Montreal, Canada, last week
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