Duluth icebreaker keeps winter maritime traffic moving

The city of Duluth, Minn. and the Aerial Lift Bridge can be seen from the top deck of the Coast Guard Cutter Alder Monday, January 14, 2013 as it begins an operation to keep the Duluth Harbor shipping channels clear of ice.
Derek Montgomery for MPR

Believe it or not, there are still ships on the Great Lakes headed for Duluth even though its harbor is clotted with ice.

Their routes are made possible by the Coast Guard Cutter Alder, stationed in Duluth to cut through the ice and keep shipping channels open. The 2,000-ton boat can ram through ice that's 3 feet thick, and leave a trail of open water — even in the depth of a Duluth winter.

Click for more photos of Duluth's icebreaker

On a recent morning, the Alder blew its whistle as it left its berth in the Duluth harbor next to the Lift Bridge. At 3 below zero with a wind chill of minus 23, the air was so cold that the whistle appeared to freeze, blowing a longer than the typical blast of four seconds.

As the 225-foot cutter moved through the last stretch of open water towards a ridge of ice, Coast Guard Petty Officer Andre Pinault stood on the bow and pointed out how the 1,000-foot vessels called lakers that haul coal and iron ore wouldn't be able to make it to their slips without the Alder.

"Especially when it gets hard, frozen over, they can't really break their own way, because the ships aren't made for that," Pinault said. "So we'll go out, we'll break tracks for them, and make sure they can keep moving their products."

As the Alder moved down Superior Bay, it hit a thin sheet of ice that cracked and split into big flat squares and trapezoids — which the crew calls "pancake" ice. Coast Guard Seaman Allyson Raby peered over the ship's edge, studying the shards as they break and crash against the hull.

"I'm just watching, checking how thick the ice is getting so I can let the bridge know," Raby said. "Right now, it's about 2 inches."

Soon, the ship hits thicker ice and slows down as it powers through the "brash" — big jagged slabs of ice left behind from prior missions that have refrozen several times. As the ice reached a thickness of nearly a foot, the Alder bounced up and down.

"We're the snow plows," said Lt. Comdr. Tony Maffia, who leads the Alder and its 50-person crew.

Maffia oversees the operation from the bridge, a high-tech center perched 50 feet above the water, with a glorious panoramic view of the harbor.

The Great Lake shipping season runs every year until about Jan. 15, when the Soo Locks close in between Lake Superior and the lower lakes. Seven ships will lay up in Duluth this winter.

Lake Superior ice
This chart shows the average percentage of Lake Superior ice coverage between Dec. 1 and May 1 over 40 years. According to professor Jay Austin at the University of Minnesota-Duluth, the term "coverage" encompasses a range of conditions. "When it shows "45 percent" that means that either: the lake was 100 percent covered 45 percent of the time, or 45 percent covered for 100 percent of the time, or (much more likely) something in between those two stages."
Courtesy professor Jay Austin at the University of Minnesota, Duluth

The Locks open up again March 25. To prepare for the new shipping season, Maffia said the Alder will begin breaking ice again in early March.

"We have what's called the break out part of the ice season," Maffia said, "where they get all the Coast Guard cutters spun up again, to do this, get the tracks ready for the lakers that are doing their first runs as soon as the locks open."

That's the time of year when ice conditions on the lake are typically most severe, said Jim Sharrow, Facilities Manager at the Duluth Seaway Port Authority.

"The ice conditions in the spring can extend well into Lake Superior, generally from Duluth to beyond Two Harbors in an average year, and in a colder than average year, you can have ice virtually across lake," he said.

In the late 1970s, several shipping companies took part in an extended season demonstration program, where they carried goods across the Great Lakes straight through the winter, Sharrow said. That was an extremely cold period, when there was as much as three feet of ice across all of Lake Superior.

"There were ships that would load in Two Harbors, and go to Gary, Indiana, and never see open water," he said.

Ice breakers had to shepherd ships across the lakes.

"We demonstrated during that time that it is technically feasible," explained Sharrow, "but we also demonstrated it has a real high reliance on very costly icebreaking."

More recently, however, the ice buildup has been much less severe. A recent study in the Journal of Climate reports a 79 percent decline of ice cover on Lake Superior since 1973. As a result, Sharrow said, shipping companies are discussing pushing back the day the Soo Locks close.

"The weather has changed quite a bit in the last 30 years, and ice on an average is forming quite a bit later than it did for a number of years," he said.

On the Duluth harbor, Coast Guard crew members slowly guide the Alder back to pier. The Alder completed its last ice breaking mission of the season Wednesday. It will start smashing through the ice again in early March.

• Follow Dan Kraker on Twitter: http://twitter.com/dankraker

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