Data shows warming eventually will shrink Great Lakes
Written by Muskegon Chronicle   
Monday, 05 February 2007 06:33

Global warming could lower water levels in Lake Michigan and Lake Huron by 5 feet over the next century, according to new data generated for a United Nations study of climate change.

Such a change would disrupt the Great Lakes shipping industry and threaten the lakes' lucrative sport fishery, according to climate experts and shipping industry officials.

Higher air temperatures also could eliminate nearly all winter ice cover on the Great Lakes in the coming decades, a change that would increase evaporation of the lakes' water, said Brent Lofgren, a physical scientist at the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory in Ann Arbor."The most extreme scenario is that over the next 100 years, we could see a 5-foot drop in water levels in lakes Michigan and Huron," Lofgren said.

Lofgren is one of several scientists working on a U.N. study of how global warming could affect the Great Lakes and other freshwater ecosystems. Expected to be released in April, the study is a follow-up to a U.N. report released Friday that said human activities over the past century have caused global warming.

Lofgren said most scientists agree that global warming will drive down Great Lakes water levels. But he said it is possible increased precipitation in the region, another expected symptom of global warming, could temper the lowering of lake levels.

A 5-foot drop in Lake Michigan water levels would widen beaches by about 100 feet, according to hydrologists at the U.S. Army Corps of Engineers in Detroit.

That would benefit shoreline property owners but cause nightmares for freighter captains and recreational boaters, who would be forced to navigate dangerously shallow waters.

"A 5-foot drop in lake levels would be catastrophic for our industry," said Glenn Nekvasil, a spokesman for the Lake Carriers Association in Cleveland. The group represents freighters that transport cargo exclusively in the Great Lakes.

Nekvasil said such a dramatic change in lake levels would require freighters to reduce loads by about 23 percent, which would drive up the cost of shipping.

The water level in Lake Michigan and Lake Huron currently is 13 inches below average, and Lake Superior is at its lowest water level since 1926, according to government data. Lakes Michigan and Huron technically are one lake, separated in name only by the Straits of Mackinaw.

Global warming also could exacerbate the recent trend toward warmer Great Lakes water temperatures. That could hurt cold-water fish species such as lake trout and salmon, the backbone of a $4.5 billion Great Lakes sport fishery, Lofgren said.

Lofgren said it is important to remember that predictions of how global warming will affect the Great Lakes are based on long-term climate trends. He said there could still be periods of brutally cold weather and blizzards during future winters, despite the projected rise in the Earth's average surface temperature.

A separate study last year concluded that global warming would reduce the surface area of Lake Erie by 15 percent by 2070. Because Lake Erie is the shallowest of the five Great Lakes, experts have said it would shrink faster than the other lakes.

A 2006 study by the Union of Concerned Scientists concluded that average air temperatures in Michigan would rise by as much as 10 degrees Fahrenheit in the winter and 13 degrees in the summer. Such changes would shorten winters and lengthen summers in Michigan, said George Kling, a University of Michigan biology professor who worked on the Union of Concerned Scientists report.

Kling said global warming is expected to increase precipitation in the Great Lakes region over the next century. But he said the added precipitation would occur primarily during winter and spring, when water levels in the lakes already are at their peak.

Reduced precipitation during the summer and a dramatic reduction in lake ice cover during the winter will increase evaporation and drive down average water levels, Kling said.

Lofgren said ice cover that forms on the open waters of the Great Lakes will likely become a thing of the past as global climate change warms the lakes. That could bring an end to the large icebergs that often form along Great Lakes shorelines during the winter.

Global warming also could devastate some of Michigan's trout streams and northern boreal forests, which rank among the state's most highly regarded natural features, Kling said.

"If you value cold-water fish, like brook trout and whitefish, and enjoy being able to angle for them in Michigan, then global warming is going to be bad," Kling said. "Those fish are going to move their range farther north and be replaced by warm water fish like carp and bass."

The predictions are similarly dire for some of Michigan's pine forests.

"The boreal forests will likely disappear by the end of the century because it will just be too warm," Kling said. "The evergreens will be replaced by oaks and hickory trees."

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