In her 2007 book Blue Covenant, Council of Canadians chairperson Maude Barlow wrote, “The Great Lakes hold one-fifth of the world’s freshwater and supply one in three Canadians and one in seven Americans – forty five million people – with their daily water use. The Great Lakes are overextended. Every day four trillion litres of water are pumped from the Great Lakes. At the same time thinner icepacks are causing increased evaporation. However, only 1 percent of the Great Lakes water is naturally renewed each year. Consequently, water levels are dropping – sometimes dramatically.”
The Canadian Press reports today that, “Normally frigid Lake Superior has warmed up faster than usual this summer due to a winter with little ice and a record-warm spring, according to researchers.”
“Surface temperatures are about 11 degrees Celsius higher than normal for this time of year and could be on their way to record highs, said researchers at the University of Minnesota Duluth’s Large Lakes Observatory. In the spring, the sun warms the water fairly uniformly as deep and shallow water mix. Once it reaches about 3.8 degrees Celsius, however, the behaviour of the water changes and warmer water starts to form a layer floating on the colder water below. The process, known as lake turnover, usually happens in mid-July on Lake Superior, but this year it happened in early to mid-June instead.”
“Climate change is responsible for the warming effect, the researchers said. ‘Lake Superior is responding to global climate shifts as clearly as anywhere on Earth,’ they said. …’There’s a climate momentum going on out there,’ (Steve) Colman (director of the University of Minnesota Duluth’s Large Lakes Observatory) said. ‘The traditional thought was that there really wasn’t any carry-over from one year to the next with this kind of system. But it looks like there is.'”
The pattern is, “The warmer the air and water, the less ice forms. The less ice, the warmer the water gets. Then less ice forms next winter.” It is unclear what effect the warmer water will have on the lake say the scientists. It could mean “a more fertile lake with more organisms that thrive in warmer conditions” or Colman says it could cause “cascading biological effects to fish and other species that we can surmise but haven’t confirmed as yet.”
“(Research Jay) Austin said UMD researchers don’t track water temperatures in the other four Great Lakes.”
WATER LEVELS
But a major new report by International Upper Great Lakes Study Board released in December 2009 found that climate change has also caused a discernible drop in the water levels of the Great Lakes. The report, that involved more than 100 scientists and engineers, estimates that Lake Huron and Lake Michigan have fallen about a quarter metre relative to Lake Erie over the last fifty years with 40-74 percent of that reduction due to climate change.
For more, please go to ‘UPDATE: Multiplicity of threats to the Great Lakes’ at http://canadians.org/campaignblog/?p=3796.
The Canadian Press article is at http://www.ctv.ca/CTVNews/SciTech/20100709/warming-lake-superior-100709/.
