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Great Lakes ice down 71 percent since 1973

DULUTH — A published report says the amount of ice covering the Great Lakes has declined about 71 percent over the past 40 years, a drop that the lead author partly attributes to climate change.

The report published last month by the American Meteorological Society said only about 5 percent of the Great Lakes surface froze over this year.

“There was a significant downward trend in ice coverage from 1973 to the present for all of the lakes,” according to the study, which appeared in the society’s Journal of Climate.

Researchers determined ice coverage by scanning U.S. Coast Guard reports and satellite images taken from 1973 to 2010. They found that ice coverage was down 88 percent on Lake Ontario and fell 79 percent on Lake Superior. However, the ice in Lake St. Clair, which is between Lakes Erie and Huron, diminished just 37 percent.

The study’s lead researcher is Jia Wang of the National Oceanic and Atmospheric Administration lab in Ann Arbor, Mich. He attributed the decline to several factors, including broad climate change and smaller cyclical climate patterns like El Nino and La Nina.