NOAA Great Lakes Environmental Research Laboratory, 2205 Commonwealth Blvd.,Ann Arbor, MI. 48105, U.S.A, Phone: 734 741 2268, Fax: 734 741 2055

Summary

        A thirty-winter (1973-2002) Great Lakes ice atlas and related publications are used for an analysis of Lake Superior ice cover. Dates of first ice, last ice, ice duration, and ice cover spatial averages and spatial patterns are analyzed within the context of lake bathymetric ranges. Results are summarized in a table, line graphs, and ice charts. Severe (mild) winters are identified based on the number of days each winter that the lake-averaged ice cover was above (below) the third (first) quartile of the 30-winter smoothed daily lake-average. Ice charts portray the spatial distribution patterns of ice cover concentrations for early, mid, and late winter and early spring for mild, typical, and severe winters. A study of the impact of global warming on the Great Lakes indicates that typical ice cover near the end of this century may be similar to mild winters described here. Such a change in the ice cover regime would impact the lake aquatic system and the regional economy.