It is happening for the last 30 years. The northern U.S. lakes have been losing annual ice cover earlier each year. A University of Wisconsin study reportedly suggests this. From 1971 to 2002, researchers re-examined ice trends for 56 lakes across Minnesota, Wisconsin, Michigan, Ontario and New York. The Duluth (Minn.) News-Tribune reported it. It found all 56 lakes had an ice breakup averaging three days earlier each decade. According to the latest study, lakes are losing faster than before 1975. 2000 researches show that lakes are losing 18 days of ice cover from 1846 to 1995. The study was led by University of Wisconsin limnologist Barbara Benson, and will be published in Science magazine early next year.