DULUTH — The U.S. Coast Guard shared its icebreaking playbook on Thursday, March 14, in advance of the March 25 start to the Great Lakes shipping season. It figures to get an assist from Mother Nature with thawing temperatures.

“I expect traffic will be moving in both directions on opening day,” said Mark Gill, Coast Guard director of vessel traffic services based at the Soo Locks in Sault Ste. Marie, Mich. “It’s going to be a challenge, with 82-83 percent ice cover on Lake Superior, but there’s a great forecast over the next 10 days, and maybe we can whittle that down in half or greater.”

The Coast Guard will use the cutter Alder and its heavy icebreaker Mackinaw, and get an assist from the Canadian Coast Guard icebreaker Samuel Risley to break out Lake Superior in the coming days.

Mackinaw and Alder will leave Sault Ste. Marie next Wednesday and cut a path along the South Shore of Lake Superior on their way to prepare tracks in the Duluth and Superior harbors.

From there, they’ll head along the North Shore through ports in Two Harbors, Silver Bay and Taconite Harbor on their way to putting “a quick fracture into Thunder Bay,” Gill said.

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The fractures all up the line help expose the ice sheet to the elements, resulting in quicker deterioration, Gill said.

The Samuel Risley will work the eastern end of the lake above the Soo Locks, clearing the way through Whitefish Bay, where ice tends to gather as if around a drain.

In April 2015, 18 vessels got stuck in ice in Whitefish Bay, where the ice was 15 feet thick. Gill sees the potential for similar accumulation this year.

“It’s premature to say we’re going to have a chaotic situation,” Gill said.

After Thunder Bay, the Alder will return to Duluth and remain at its home port, while the Mackinaw will head to Whitefish Bay, sending the Samuel Risley up to Thunder Bay. The Alder will concentrate on keeping the Duluth and Superior entrances open and shipping channels clear, while local tug operations work the ships in and out of the docks, Gill said.

Not all vessel companies will risk the early going.

Canadian National Railway’s Great Lakes Fleet, based in western Duluth and operated by Key Lakes Inc., will keep itself grounded until April 1, Gill said. Other companies will follow suit.

“They’re sacrificing the early start and instead they’re playing the long game,” Gill said, explaining that puncturing a hole in a ship’s hull can cost up to $4 million to repair and put a ship out of commission in the meantime.

“These companies operate on razor-thin margins,” Gill said. “Sometimes it’s OK to be slower out of the gate with the promise of more production to come. Some companies don’t have that option.”

Taconite iron ore shipments figure to take up the bulk of the early movement. Blast furnaces at steel mills down the lakes have worked through stockpiles and are ready for replenishing.

When it comes to sailing through the ice, speed will be a factor.

“They’re trying to get product to industry,” Gill said. “But they have to be careful. You don’t want to come up at lake speed on a field of ice 24 inches thick.”