With temperatures falling and ice beginning to form in the Straits of Mackinac, the U.S. Coast Guard cutter Mackinaw is preparing for the 2009-10 icebreaking season.

The 240-foot vessel returned to its mooring at Cheboygan, Mich., about a week ago after sailing up the St. Marys River to survey channels, islands and passageways it will navigate when solid ice forms.

The Mackinaw is one of eight Coast Guard icebreakers dedicated to keeping shipping lanes clear in coordination with commercial shipping interests and the Canadian government.

The cutters engaged in Operation Taconite will break ice in lakes Superior and Michigan, northern Lake Huron, the St. Marys River and the Straits of Mackinac between lakes Michigan and Huron.