Ice cover on the Great Lakes has decreased by 71% over the past four decades according to a new study published in February, 2012 in the Journal of Climate.
The Great Lakes, located in eastern North America, contain about 20%
of the world’s surface supply of freshwater. The ice cover that forms
over the Great Lakes every winter plays a critical role in regulating
water levels, structuring the lakes ecosystems and impacting the
regional economies that depend on cargo shipments and hydropower
generation.
In a study led by Jia Wang, an Ice Climatologist with the National
Oceanic and Atmospheric Administration’s (NOAA) Great Lakes
Environmental Research Laboratory in Ann Arbor, Michigan, scientists
investigated ice cover on the Great Lakes from 1973 to 2010. Data were
obtained from NOAA’s National Ice Center and from the Canadian Ice
Service. These federal agencies have been collecting data on ice cover
since the 1960s through both satellite imagery and visual observations
made from airplanes.
The scientists found that all of the Great Lakes have lost ice over
the past 38-year period. Lake Ontario had the greatest amount of ice
cover loss (88%), while Lake St. Clair lost the least amount of ice
cover (38%). Overall, the total loss for Great Lakes ice cover was 71%.
The scientists observed that ice cover on the Great Lakes is highly
variable from year to year. The scientists attribute the variability in
ice cover to natural climate forcing patterns that result from impacts
of the Arctic Oscillation and the El Niño Southern Oscillation on
surface air temperatures in the region. They note that long-term trends
in Great Lakes ice cover may also possibly be related to global climate
warming.
Their research was supported by grants from the National Research
Council and the U.S. Environmental Protection Agency’s Great Lakes
Restoration Initiative.
Since 2010, ice cover on the Great Lakes has continued to be highly variable.
According to data from the Canadian Ice Service,
ice cover on the Great Lakes for the week of March 5, 2011 was about
36% and close to the historical average of approximately 38%. However,
ice cover for the week of March 5, 2012 has been exceptionally low and
only amounts to about 12%.
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