The analyses of the Great Lakes Environmental Research Laboratory's (GLERL) historical ice cover data during 1973–2021 indicate that warmer winters with reduced surface ice cover have become more frequent in the last two decades (1995–2021) compared to the previous decades (1973–1995) in the Great Lakes. In the past two decades, for example, years with lower-than-normal ice cover have become more frequent in Lake Superior, which has a history of freezing almost completely. These observations suggest a ...