DULUTH, Minn. (AP) _ A U.S. Coast Guard cutter has started ice breaking activities in the Twin Ports of Duluth and Superior, an annual ritual that signals the approach of spring.

The cutter Alder began cleared the channels Tuesday for the upcoming shipping season. It's so the 1,000-foot long ships loaded with taconite, coal, limestone and other cargo can maneuver through without getting stuck.

Reports say the Coast Guard is also responsible for maintaining the ports in Two Harbors and Silver Bay and may help break ice in the Thunder Bay, Ontario harbor.

The Great Lakes shipping season begins March 25.