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Climate change and the Great Lakes

NASA imagery depicting the Great Lakes (courtesy: NASA)
NASA imagery depicting the Great Lakes (courtesy: NASA)

Cheryl Santa Maria, staff writer

August 11, 2012 — It's the largest source of surface fresh water in the world and an economic hub for Canada and the U.S. But a steadily-mounting body of research shows that the Great Lakes are changing, and warmer weather may be the cause.

NASA imagery captured on October 5, 2011 depicting algal blooms (in green) in Lake Erie (courtesy: NASA)
NASA imagery captured on October 5, 2011 depicting algal blooms (in green) in Lake Erie (courtesy: NASA)

Earlier this month, researchers at the University of Duluth revealed that the temperature of Lake Superior - the coldest and deepest of the bodies of water that make up the Great Lakes - is sitting at about 20C, the warmest it's been in a century.

The temperature spike has been attributed to minimal ice cover during the winter, combined with above-average warmth in the spring and summer.

Data suggests that the warmer weather is part of a trend. On Thursday, scientists revealed that three out of the five hottest months in the history of the U.S. were in 2012, 2011 and 2006 respectively, and climate change is the likely culprit.

It's a significant shift that has many researchers paying attention. After all, a rising temperature has the potential to impact just about everything -- including the Great Lakes.

Spanning over 243,000 square kilometres and comprised of lakes Superior, Michigan, Huron, Erie and Ontario, the Great Lakes provide drinking water to more than 40 million people. Tourism, recreational and commercial activities account for billions of dollars in revenue and provide countless jobs on both sides of the border.

A 2009 study conducted at the University of Rhode Island was one of the first to provide tangible evidence that the Great Lakes are sensitive to a changing climate. Extreme drought caused water levels in the lakes to shrink by about 20 metres between 7,900 and 7,500 years ago, dispelling the long-held belief that the shift was a result of glacial activity.

"Our study showed that in an extremely dry climate regime the Great Lakes are 'sensitive'," explains Dr. John King, who led the study.

"If the severe drought conditions currently occurring in the [American] west and mid-west were to continue for a few years, we might see changes that exceed the range of variation observed in the last few millennia."

While Dr. King contends that it is "difficult to predict" if water levels in the Great Lakes will shift in the future, his study draws attention to how much of the North American economy hinges on the Great Lakes, in their current form.

"As water levels decrease, loads of shipping vessels would need to be decreased and shipping costs would increase," he says. If levels were to dwindle "to the point that the Great Lakes were no longer connected and shipping was halted, that would be very bad."

For now, levels appear to be in-tact -- but that doesn't mean the Great Lakes have been spared from the effects of warmer weather.

Algal blooms appear to be worsening in Lake Erie (courtesy: Garth Chivers)
Algal blooms appear to be worsening in Lake Erie (courtesy: Garth Chivers)

Toxic algal blooms thrive in warm conditions, and they've been doing exceptionally well in Lake Erie since 2002.

In fact -- "last year the algal bloom in Lake Erie was 2.5 times larger than anything we've ever seen in the past," says Dr. Jeffery M. Reutter, Director of the Ohio Sea Grant College Program at Ohio State University. "It covered the water intake [structures] for more than 8 million people in the Cleveland area."

It's more than just unsightly. In addition to turning parts of the lake murky green, algae is toxic and costly to clean up.

Phosphorus, a chemical element commonly found in household fertilizers and cleaning products, has exacerbated the issue. When runoff containing the composite makes its way into the lake, blooms abound.

Dr. Reutter says the problem can be curbed by improving agricultural and sewage treatment practices.

He recommends choosing household cleaning products and fertilizers that are low in phosphorus and trying to keep water out of storm sanitary systems. This can be done by installing rain barrels and switching to low-flow toilets and showers.

These small adjustments can have a positive impact on Lake Erie when carried out by a large group of people.

The Great Lakes "provide tremendous resources for drinking water and tremendous value for tourism and the economy," Dr. Reutter says. "They are a sustainer of life and the economy -- and not just for the regions surrounding the lakes, but for the U.S. and Canada as a whole."

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