Undercurrents: beneath the obvious

January 10, 2008

The evaporation factor: Warm winter weather + frozen ground = lower lake levels

Filed under: Great Lakes Issues,Lake Levels — nemo @ 12:17 pm

Lake levels continue to decline. This article explains the reasons quite nicely. Notice that average lake temperatures have increased 4 degrees since 1980.

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, and much of that water evaporated into the air. The cycle has been playing out for the past 30 years in the Great Lakes, said Cynthia Sellinger, co-author of a paper to be published Tuesday 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.

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.

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 the 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 inches lower than a year ago.

Part of the reason for Lake Superior’s rise is about 10.5 inches of rainfall in the basin during September and October, right at the lake’s low point, said Keith Kompoltowicz, a meteorologist for the Army Corps in Detroit. [From The Bay City Times]

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2 Comments »

  1. Might sound like a daft question but if the water evaporates its not lost to the planet as water its going to come down somewhere – anyone traced where that is?
    I’m getting intrerested in patterns of water movement.

    Comment by Pamela — April 20, 2008 @ 4:26 am | Reply

  2. Great resource thank you. I used it in my classroom for part of a lesson plan and just wanted to thank you. I wanted to share the other resource I used as well.

    http://www.thefreeresource.com/the-great-lakes-facts-and-resources-about-lake-michigan-huron-erie-superior-and-ontario

    Bre
    8th Grade Teacher
    North Carolina

    Comment by bre — November 16, 2010 @ 1:53 pm | Reply


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