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Lake Erie's Dead Zone Growing
A continuing trend of hot summers and warm winters may shrink the surface area of Lake Erie by as much as 15 per cent over the next 50 years, affecting thousands of municipal waste intakes and wells, increasing the size of the lake's "dead zone" and leaving marinas high and dry.
That grim forecast was outlined by scientists at the Third Biennial Conference of the Lake Erie Millennium Network that continues today at the University of Windsor.
As temperatures continue to rise in the northern hemisphere, scientists predict the level of Lake Erie could be reduced by as much as 83 cm by 2050.
"Weather is a primary factor in determining lake levels," said Bryan Tugwood, of the Meteorological Service of Canada's Ontario Region. "We've had very high water levels for the past 30 years, with the exception of the last five."
Working from a series of climate models, Tugwood said the temperature is expected to continue to rise in the Northern Hemisphere over the next 100 years.
He said that from 1977 to 1999 the Great Lakes had the highest water levels recorded for more than a century because of increased rainfall. But since 2000, the lowest water levels in 100 years were recorded. He said the 1990s was the warmest decade and 1998 the warmest year.
"Five of the 10 warmest winters recorded have occurred since 1998," Tugwood said. "That means less winter snowpack and less spring runoff. Though the region had a cold winter this year, there was 20- to 40-per-cent less precipitation. All lakes are below average water levels. Lake Erie is 24 cm below average and the prediction is for it to stay 22 cm below 2000 levels."
He said Lake Erie's in-shore water temperatures are already warmer than average. With lower ice cover, a later freeze up in the fall and an earlier breakup of ice in the spring, the lake could be down by 60 cm or more by 2030 -- wreaking havoc on marinas and recreational activities like ice fishing and skiing. Cold water fish like lake trout stand the risk of extinction in Lake Erie, to be replaced by more species of warm water fish.
Tugwood said the lake could be down 60 cm by 2030 and by 2090 the lake could be completely ice-free as early as February.
The conference, created in 1999 by University of Windsor biologist Jan Ciborowski of the Great Lakes Institute to conduct research on the management of Lake Erie, brings together dozens of prominent environmental scientists, researchers and managers from Canada and the U.S. to review and share new results.
Ciborowski, who has been conducting research on Lake Erie's "dead zone" -- an oxygen-deprived area devoid of life in the deepest parts of the lake -- said studies show the zone is affected by the warming climate. Oxygen supply near the bottom of the lake is getting cut off by warmer layers of water near the surface. As the water level decreases, the lake becomes warmer, creating the potential for a larger dead zone.
But there are other culprits. Ciborowski said research has found that increasing levels of phosphorous from sewage runoff is creating more algae, which in turn attracts more of the bacteria that feed off it. High levels of bacteria can deprive the water of oxygen, he said.
Scientists say the ideal way to reduce the dead zone would be to deepen the lake and cool its temperature -- an unlikely solution.
- Sun, 5/11/2003
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