Great Lakes Ice Cover Melting Away
Friday, March 23rd, 2012March 23, 2012
The amount of ice covering the five Great Lakes in winter has decreased significantly, says a new report, and researchers warn that the loss could have a substantial impact on water quality and habitats in the region. The report, released by the American Meteorological Society (AMS), identifies an average decline of about 71 percent over the past 40 years. Measured losses vary from year to year and lake to lake. The Great Lakes are Lakes Erie, Huron, Michigan, Ontario, and Superior.
Researchers examined satellite photos and United States Coast Guard reports of ice coverage from 1979 to 2010. Lake Ontario, the smallest of the Great Lakes, showed the biggest decrease, with coverage falling by 88 percent. Coverage fell by 79 percent on Lake Superior, the largest of the lakes. The AMS also noted that only about 5 percent of the Great Lakes’ surface froze over this winter, though those data do not appear in the report. On average, the lakes have about 40 percent coverage in winter.
Together, the Great Lakes make up 18 percent of the world’s fresh surface water. Shrinking ice coverage on the lakes may speed up wintertime evaporation, leading to lower water levels and increased erosion along the shoreline. Lack of ice may also lead to an increase in algae blooms, which damage water quality.
The Great Lakes are the world's largest group of freshwater lakes. Declining levels of ice coverage may threaten the lakes and their surrounding habitats. (World Book map)
The report’s lead author, Jia Wang of the National Oceanic and Atmospheric Administration (NOAA) lab in Ann Arbor, Michigan, says the loss may be at least partly the result of climate change. Wang also noted that smaller climate patterns, such as El Nino and La Nina, may have played a role. “We are seeing the impact of global warming here in the Great Lakes,” says Wang, “but the natural variability is at least as large a factor.”
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