This tranquil scene of an icebreaker leaving harbor belies the fact that from December until spring, ice owns the Great Lakes. In 2015, more than 80 percent of the surface water was frozen; Lake Erie was 94 percent covered in March. In 2013-14, there was ice on Lake Superior into June.
When the cold winds blow, the ice is often pushed and shoved across the freezing waters to be swept into busy bays and harbors. In blocks, bergs and sheets up to 5 feet thick, it piles on itself, jamming tight against bridges and docks, and turning roadsteads and anchorages into jagged white parking lots filled with iced-in, non-moving shipping.
That’s when the icebreakers get to work. With two 2,500-hp diesels turning an 8-foot propeller and driving an inch-thick steel hull, they’re made for the job. Top speed is 14 knots, but it’s power that counts when you’re driving a ship into an ice floe.
There’s more to breaking ice than bashing into it. Heavy ice is dealt with by riding up onto it and using the ship’s weight to break it into large chunks. Sucked into the prop wash, the pieces are broken even more. The helmsman also can rock the ship from side to side in a technique called sallying, making waves to break up locked-in ice.
Race-tracking describes the vessel making a series of loops through the ice pack, breaking up pieces that are small enough for the current to carry away. And when a channel is finally cleared, the icebreaker shaves its edges clean, being careful not to break off a floe that might jam things again.
There are nine of these vessels on the Great Lakes, keeping open the big commercial ports — Detroit, Chicago, Cleveland — and keeping the grain and coal freighters running. The icebreakers’ motto: “We move ships when no one else can.”
The Coast Guard icebreaker Mackinaw, known as the “Queen of the Great Lakes,” serves as a museum in Mackinaw City, Michigan. She is open for tours, educational programs and overnight encampments. themackinaw.org
This article originally appeared in the February 2017 issue.
