Headed south for the winter: Icebreaking 101

This blog is part of a series following Coast Guard Cutter Polar Star on their journey to Antarctica in support of Operation Deep Freeze 2015.

Written by Petty Officer 1st Class George Degener

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, breaks a parallel channel in the ice beside a previous channel near the National Science Foundation's McMurdo Station, Antarctica. As the area of broken ice widens, southerly winds will push the ice out to sea, allowing supply vessels to deliver cargo to McMurdo Station. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, breaks a parallel channel in the ice beside a previous channel near the National Science Foundation’s McMurdo Station, Antarctica. As the area of broken ice widens, southerly winds will push the ice out to sea, allowing supply vessels to deliver cargo to McMurdo Station. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

A long straight light blue line of crushed ice and water extends from Cape Evans, Antarctica, interrupting the vast field of white stretched across the frozen waters of McMurdo Sound near Ross Island. Normally, the only spots of color are exposed patches of brilliant blue ice and the occasional penguin or seal.

At the end of the blue line is the red hulled Coast Guard Cutter Polar Star, the nation’s only operational heavy icebreaker. The ship carved a 20-mile track extending from the open waters of McMurdo Sound to a turning basin near Winter Quarters Bay. At the end of the pathway in the 3 to 7 foot thick ice is the National Science Foundation’s McMurdo Station.

Simple physics explains the process of icebreaking: two objects cannot occupy the same space at the same time. The 150-person crew of Polar Star uses that principle to open the channel for cargo and fuel ships to deliver vital supplies to the scientists and support personnel at McMurdo Station as part of Operation Deep Freeze. Operation Deep Freeze provides military logistical support as part of the NSF-managed U.S. Antarctic Program.

“The officers of the Deck and Conning Officers are expected to make a straight channel from the ice edge to the turning basin,” said Capt. Matthew Walker, commanding officer of Polar Star. “Then, they widen the channel to at least three ship widths, and finally, their job is to make the remaining ice small enough that if the wind doesn’t blow it all out to sea, the supply ships can still safely transit through the area.”

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, breaks ice near the National Science Foundation's McMurdo Station, Antarctica. Polar Star's crew is in Antarctica supporting Operation Deep Freeze 2015, part of the U.S. Antarctic Program, managed by the National Science Foundation. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, breaks ice near the National Science Foundation’s McMurdo Station, Antarctica. Polar Star’s crew is in Antarctica supporting Operation Deep Freeze 2015, part of the U.S. Antarctic Program, managed by the National Science Foundation. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

The officers and senior enlisted crewmembers who run the bridge on the ship must understand the important role of weather and ice conditions. During the journey across the Southern Ocean and Ross Sea prior to arriving in their operating area for Operation Deep Freeze, the ship’s crew dodged strong Antarctic storms and encountered ice fields further from shore than experienced in previous years.

“This year there was quite a bit of pack ice, which is sea ice that formed over the winter, broke off and drifted offshore,” said Cmdr. Kenneth Boda, executive officer of Polar Star. “When we were coming south we had to transit through about 200 to 300 miles of pack ice, almost all the way across the Ross Sea.”

The ship receives a combination of satellite and radar imagery from the U.S. National Ice Center. Data transmissions include areas of ice concentration and thickness, and allow ship handlers to determine the safest route to McMurdo Station.

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, breaks ice near the National Science Foundation's McMurdo Station, Antarctica, Jan. 13, 2015. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, breaks ice near the National Science Foundation’s McMurdo Station, Antarctica, Jan. 13, 2015. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

Once the initial channel is cut, the Polar Star crew will attempt to expand the channel by cutting a series of angles towards open water. If favorable, southerly winds will then carry the wedge-shaped pieces of ice out to sea. Scarfing, or driving a close parallel track to the initial cut, also widens the channel. When the channel is wide enough, the crew will continue grooming by breaking the ice into slush that other vessels can safely navigate through.

When transiting through the ice, intense vibrations and noise permeate through the 399-foot cutter. Gas turbine engines, similar to those found in jets, provide power. This forces the bow of the icebreaker to ride onto the fast ice. The weight of the ship will then break the ice, which heads back along the hull and passes through the screws, creating a din that can give operational clues to the experienced ear.

“Listening to and feeling the ice can really tell you what’s going on outside,” said Boda. “If you’re bouncing around, you know you’re breaking new stuff, and if you’re sliding around, you know you’re breaking through old stuff.”

The cutter’s crew continues to break through the ice allowing supply and fuel ships to arrive safely at McMurdo Station. The crew’s efforts allow scientific work to continue, providing support for scientific discoveries that benefit the entire planet.

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, sits moored at the ice pier at the National Science Foundation's McMurdo Station, Antarctica. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

The Coast Guard Cutter Polar Star, a heavy icebreaker homeported in Seattle, sits moored at the ice pier at the National Science Foundation’s McMurdo Station, Antarctica. U.S. Coast Guard photo by Petty Officer 1st Class George Degener.

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