DULUTH – The reinforced hull of the 225-foot U.S. Coast Guard Cutter Alder scraped loudly through the ice in the harbor. With each advancing inch, it sent cracks into a marbleized sheet, breaking it into crumbled pieces.

The sure sign of spring — ice breaking in Lake Superior Harbor in preparation for shipping season — is relatively easy this year, with ice only about a foot thick in some spots.

"This is a weird year," said Lt. Cmdr. Justin Erdman, the ship's captain, as he surveyed the frozen industrial back bays from the upper deck of the Alder, the vessel trembling only a bit as it plowed ahead under little resistance. "Most winters we're backing and ramming to break the ice."

Mild temperatures left the Great Lakes at only 19.5% ice cover this year — the fourth-lowest percentage on record, and far less than the mean maximum ice cover of 54%. Lake Superior has mostly open water this year, with only 7% ice coverage as of Tuesday, compared with more than 86% coverage last year at this time.

So it may be a hard sell for shipping companies and associations that are urging the federal government to invest in more and better ice-breaking equipment, saying that slowed ice breaking in cold winters can mean hundreds of millions of dollars of economic loss, including damage to cargo-carrying vessels.

In 1979, 20 icebreakers roamed the Great Lakes, but now there are just 11 — nine from the United States and two from Canada. Many of the vessels are aging and are sometimes out of commission for repair.

Shippers say the inability to break up the ice quickly can often delay moving goods and materials for a week or two because vessels would be damaged too much. That period of time is critical to keeping steel mills and power plants operating, they argue.

"In really bad years, it'll go beyond a month, a month and a half," said Ken Gerasimos, general manager of Key Lakes Inc., which operates nine cargo-carrying vessels out of the Duluth-Superior Port. "Last year was a pretty good indicator, it was totally inadequate. … You're incurring damage to the ships."

The Lake Carriers' Association is pushing for another heavy icebreaker like the Coast Guard's Mackinaw, a 240-foot brute that can cut through ice 32 inches thick and is stationed in Michigan on Lake Huron.

The Great Lakes have only one such ship now and could use a second, said Eric Peace, association communications director.

Last year — an especially difficult ice year — the economy took a hit of more than a billion dollars because of inadequate ice breaking, Peace said.

"We'd take two or three of them. One of them is what we need right now," he said.

The cost for a new ship is estimated at more than $160 million. While Congress has authorized its construction, it has not yet appropriated all the money needed to acquire it.

"The problem is that winters like this year will make it a short-term memory loss," Peace said. "Then next year we'll have another horrific ice year."

While the Coast Guard typically keeps top-tier waterways open, he said, their operations are akin to using a limited number of snowplows to clear freeways, but keeping on-ramps and smaller roads blocked, so not many vehicles can even reach the main roads.

The Alder is cutting those paths easily this year as it maneuvers around the Duluth-Superior Harbor. The vessel, designed for setting buoys during open water months, is capable of cutting through 18 inches of ice or ramming through 3 feet of it.

After leaving its home port on the bay side of Park Point, the Alder made a few ice-breaking circles in the St. Louis Bay north channel, near the Canadian National ore docks, and the south channel near the Midwest Energy Terminal, then it went to Howards Bay to break a path to Fraser Shipyards. Later, it made a path through the Superior Front Channel toward the Burlington Northern Santa Fe ore dock.

While the Alder is only 49 feet wide — not nearly enough for a 1,000-foot laker to squeeze through — the initial ice breaking will make it easier to break more paths later so ships can get out in plenty of time for the March 25 opening of the Soo Locks, Erdman and others said.

"We'll widen it out over the next couple of days," he said.

Depending on conditions, the Alder will often accompany vessels through tough spots.

While the Alder cut through harbor ice this week, some of the crew on board wondered aloud whether, with milder winters, shipping could someday run all year.

That would require a second Soo Lock capable of handling big ships, so that there is time for lock maintenance, Peace said. Plans are underway for construction of that lock.

When that is completed, industry might be ready to think about year-round Great Lakes shipping.

"It's possible. … We're not necessarily advocating for that right now, but maybe in the future depending on what the conditions are," Peace said. "We'd still need the icebreakers to do their work, and we'd probably need more of them."

Pam Louwagie • 612-673-7102