Springtime in Duluth isn't signaled by birds or butterflies or flowers.
Duluthians know it's spring when the Coast Guard icebreakers arrive, announcing the start of another Great Lakes shipping season.
• Photos: Duluthians skate the 'People's Rink' on frozen Superior
• The secret lives of wolves in Voyageurs National Park: They fish and eat berries
• A return to Superior's ice: This time without her husband but with women angler community
Last week, two cutters carved a track from the Soo Locks on the eastern edge of Lake Superior all the way to Duluth. The Mackinaw then cut a path up the North Shore, breaking open paths in the ice and clearing the way for thousand-foot freighters to carry their first cargo of iron ore, coal and grain.
But the U.S. Coast Guard cutter Alder stayed behind to break up the ice in the Duluth-Superior harbor.