The first ships to shoulder their way west through the Lake Superior ice sheets reached Duluth Monday morning.

Brutal winter cold covered the Great Lakes in thick sheets of ice and delayed the start of the 2014 shipping season. The first ship to cross the stretch from the Soo Locks to Duluth around 6 a.m., a convoy edging through the ice with a Coast Guard escort

Star Tribune file photo.

Star Tribune file photo.

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The Stewart J. Cort passed under the Aerial Lift Bridge first, followed a few hours later by the Mackinaw, Sam Laud and Algoma Discovery, according to the site boatnerd.com. The convoy left Whitefish Bay last week.

U.S. and Canadian coast guard ships will be escorting convoys until the icy shipping lanes are safer.