Researchers in Michigan are pointing at new evidence that water levels in the Great Lakes, which are near record low levels, may be shrinking due to global warming.

The new study, points out that water levels in the Great Lakes, which supply drinking water to more than 40 million United States and Canadian residents, have fluctuated over thousands of years. However, recent declines in water levels have raised concern because the declines are consistent with many climate change projections.

Alex Zelaya
www.thirdeyeconcept.com

Director of Grand Valley State University's Annis Water Resources Center, Alan Steinman - recently stated that one of their researchers studying wetlands around lakes Michigan and Huron had seen four of the six wetlands he monitors around Saginaw Bay dry up. "Those wetlands are now dry lands," he said.

Great Lakes water levels go down every fall, rise in the spring and fluctuate in longer cycles spanning roughly 30 years. But water levels in lakes Michigan, Huron and Superior have been dropping steadily over the past decade. Lake Superior, the largest body of fresh water in the world by surface area, is experiencing its lowest water levels since the record set in 1926. The lake is down by 34 centimetres from a year ago, and more than half a metre below its long-term mean.

Current water levels in Lake Michigan and Huron are about 3.5 inches above the record low water levels recorded in 1964, according to U.S. Army Corps of Engineers data. But there are indications water levels in the lakes, which have dropped nearly four feet since 1998 and are 26 inches below their long term average, will continue to fall.

Low lake levels caused problems for some freighters trying to get into Muskegon Lake this summer; some ships had to lighten their loads by 15 percent to avoid running aground. The Mona Lake channel also dried up twice this year as Lake Michigan's water level continued its steady descent. Natural beds of wild rice growing in the lake's shoreside wetlands and harvested by Native Americans are also threatened. The long-term effects of prolonged warming on Lake Superior's aquatic ecosystems are not yet known.

Need for cold weather

Jay Austin, a limnologist with the University of Minnesota Duluth's Large Lakes Observatory commented that Superior's surface waters had warmed by about 2.5 °C since 1979 - far more than average air temperatures in the region during the same period. Austin's findings link the warming to a reduction in winter ice cover on the lake. The less ice is present to reflect sunlight, the more solar energy the lake can absorb. On average, the onset of summer warming of the lake is happening half a day earlier each year. The reduced ice cover also contributes to shrinkage by allowing more evaporation. "Most of the evaporation goes on in winter," Austin says, as cold, dry air swoops over the warmer lake. Without the ice cap to block evaporation, water losses increase.

And Cynthia Sellinger of the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan, agrees. While the lake's level has dropped precipitously, Sellinger has tracked a longer-term decline of an average of 10 millimetres per year since 1978. Evaporation has increased by an average of 4.6 millimetres per year, she says, while precipitation has decreased by 4.1 millimetres per year. These drops are consistent with climate change models, Austin says, which predict a decline in Great Lakes levels of 0.5 to 2.5 metres with a doubling of atmospheric carbon dioxide.

About 31 percent of the water lost from lakes Michigan and Huron is due to evaporation. In November, the volume of precipitation falling on lakes Michigan and Huron broke a record low established in 1908.

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