One aspect of the Coast Guard’s 11-part mission is to keep shipping lanes open and facilitate commercial maritime activities across the Great Lakes and the Northeast, as well as provide year-round access to polar regions.
In the winter — and in polar regions throughout the year — that translates to using icebreakers to clear transit lanes and free ships trapped in ice.
The Coast Guard launched its first true icebreakers in the 1940s. The Wind Class ships were 270 feet and displaced 6,500 tons of water. Their diesel engines had a range of 32,485 miles.
This video has more:
Previously the Coast Guard (and its predecessor, the U.S. Revenue Cutter Service) used sail-powered vessels typically built for other uses — for instance, SS Bear, which was launched in 1874 and had been built for sealing in the eastern North Atlantic.
The Revenue Service purchased the ship in 1885 and found that its 6-inch-thick wooden hull was ideal for Arctic exploration and icebreaking.
This Soundings article has more about icebreakers and the way they work.