Thursday, January 10, 2008

"Warm-winter cycles accelerating loss of Great Lakes water"

Lake Huron is in a fog, part of a gloomy cycle that's pushing water levels to record lows, scientists say.

Last week, a winter storm dropped more than a foot of snow over the Great Lakes. Over the weekend, warmer temperatures melted that snow, which evaporated into the air.

The cycle has been playing out for the last 30 years in the Great Lakes, said Cynthia Sellinger, co-author of a paper to be published Saturday in Environmental Science & Technology, a scientific journal.

Winters have been warmer. Snow doesn't build up, then seep into the ground and recharge the lakes in the spring.

Instead, warmer winter temperatures melt the snow after it falls, leaving the ground frozen and allowing the snow to evaporate.

"Since 1978, there's been a long-term decline in precipitation and a long-term increase in evaporation," said Sellinger, a hydrologist at the Great Lakes Environmental Research Laboratory in Ann Arbor, an arm of the National Oceanic and Atmospheric Administration.

"It's very subtle, extremely subtle, but it's there."

Lakes Huron and Michigan, which are connected by the Straits of Mackinac, are experiencing the lowest water levels in the Great Lakes this month.

Lake Huron is within 2 inches of its all-time low for January, according to data from the U.S. Army Corps of Engineers. The lake is 14 inches lower than it was at this time last year.

It's projected to dip another inch during the next month, as part of its seasonal decline.

Sellinger said it's possible that Lake Huron will break its record low for January, set in 1965, later this month...

Temperatures in the Bay City area were expected to reach 53 degrees Fahrenheit on Monday, topping a record of 50 degrees from 1989, according to the National Weather Service.

Since 1980, when NOAA temperature buoys were installed, the surface water temperature of Lakes Michigan and Huron has increased by about 4 degrees Fahrenheit, according to Jay Austin, a researcher at the Large Lakes Observatory, part of the University of Minnesota in Duluth.

"It's larger compared to what we've seen in the atmosphere," or about twice the rise in global air temperatures attributed to global warming, Austin said.

Lake Superior is only Great Lake seeing higher levels this January. It's 6 inches higher than at this time last year. The rest of the lakes are 11-16 lower than a year ago.

Part of the reason for Lake Superior's rise is about 10.5 inches of rainfall the basin saw in September and October, right at the lake's low point, said Keith Kompoltowicz, a meteorologist for the Army Corps in Detroit.

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