Great Lakes Winter Commerce Act of 202 1 This bill directs the U.S. Coast Guard to conduct icebreaking operations in the Great Lakes in accordance with specific performance standards. Specifically, the Coast Guard must keep channels and harbors in the Great Lakes open to navigation not less than 90% of the hours that commercial vessels and ferries attempt to transit ice-covered waterways; and in a year in which the Great Lakes are not open to navigation because of ice of a thickness that occurs on average only once every 10 years, keep channels and harbors open to navigation at least 70% of the hours that commercial vessels and ferries attempt to transit ice-covered waterways. Additionally, the Coast Guard must establish and maintain a database for collecting, archiving, and disseminating data on icebreaking operations and commercial vessel transit in the Great Lakes during ice season. The bill also directs the Coast Guard to acquire a Great Lakes icebreaker that is at least as capable as Coast Guard Cutter Mackinaw. The Government Accountability Office must submit to Congress a report on the Coast Guard Great Lakes icebreaking program.