Channel Breakout

	Polar Star can deliver 75,000 shaft horsepower when breaking ice on its three gas turbines. Photo courtesy of www.polarstar.org

The primary task involves cutting an access channel through the ice in McMurdo Sound, to allow resupply ships to go alongside the ice pier at McMurdo Station.

This "seasonal" ice is called "fast ice" because it is made fast to the shoreline and is not adrift. The fast ice in McMurdo butts up against the Ross Ice Shelf just south of Scott Base, about three miles south of McMurdo. It is approximately three feet thick at the northern ice edge and can be from eight to 14 feet thick at McMurdo. The fast ice edge (i.e., the required length of the channel) can range from eight to 50 miles north of McMurdo.

The channel should be approximately 200 yards wide at Hut Point, just off McMurdo Station, and pass 1,500 yards abeam of the point. The ship usually begins the breakout on or about Jan. 1 and reaches McMurdo Station 24 to 48 hours later. Channel "grooming" operations can continue for the duration of the deployment.

The First Cut (break-in)

The ship will normally make the first cut using turbines. It's tough, slow going, normally taking anywhere from 24 to 48 hours depending on the length of the run. Although not under pressure, the solid sheet ice of McMurdo Sound will not give the broken ice any place to go: hull and ice will try to occupy the same space at the same time. Subsequent cuts are much easier as newly broken ice can easily slide into the previous cut, and the ship can usually finish the job on diesels.

If the channel is cut with reasonably straight sides and in a slight "V" shape, southerly winds will blow most of the broken ice into the open water. This is why Polar-class sailors hope for southerlies in early January -- they're looking for a good strong low to blow across the Ross Ice Shelf and into McMurdo Sound. If the southerlies don't blow, the channel will be filled with fairly heavy brash and will be navigable only with escort.

Turning Basin Breaking

A circular basin is then cut out just off Winters Quarters Bay (McMurdo) to allow the resupply ships to back out, turn north and head for the channel. Usually, the ships will require the icebreaker to provide tugboat services. The tanker (and sometimes the resupply ship) will usually need a pull to start backing out, then a pull to get their bow headed fair for the channel. If the turning basin is clear, allowing the basin ice to follow, this evolution can be fairly routine. If not, it can be extremely interesting and a chance for the Polar-class sailors to do some pretty close shiphandling.

Ice Pier Scarfing

Although covered with dirt, and frequently mistaken for the shoreline, the pier at McMurdo is a solid block of ice. Shortly before the resupply ships are scheduled to arrive, the icebreaker will scarf (shave) the edge of the ice pier to ensure a slab-side for the ships to lay on. This scarfing is done with the ship's bow, in a slow process. The ice pier can, and will, break into pieces if scrafed incorrectly.

Marble Point Resupply

Polar Star provided about 65,000 gallons of fuel to the Marble Point helicopter refueling station. Photo courtesy of www.polarstar.org

Marble Point lies about a half-day steam northwest of McMurdo Station. It consists of a few small huts and several fuel tanks, holding about 120,000 gallons of JP5 aviation fuel. Refueling at Marble gives the McMurdo helicopterss the legs to get up into the Dry Valleys and Victoria Land coast, both heavily researched areas. The ship will get as close to the beach as possible (usually about one-quarter of a mile), moor itself in the ice and transfer about 65,000 gallons to the tanks.

Major problems in the past resulted from the icebreakers having to wait for the tanker (usually around Jan. 20) to load the JP5 for transfer to Marble. By that time, the ice around the point had broken up, leaving nothing to securely hold the ship, with the fuel hose running through water, from floe to floe.

However, a cure was found in 1992 when Polar Star loaded 80,000 gallons of JP5 at Manchester Fuel Depot in Seattle prior to deploying and was able to make the transfer early in the season. Polar Sea made the first several cuts for the channel, then headed to Marble in early January, well before the tanker's arrival, and well before the ice had broken up. The entire evolution took place on an ice shelf approximately 6 feet thick, making fuel line checks and ship positioning extremely easy.

Ice Escort

Normally, when the resupply ships arrive at the ice edge, there is still enough brash in the channel to make escort duty necessary.

The channel escort is a fairly routine evolution done at about 5 knots, with the breaker staying anywhere from 100 yards to a quarter-mile in front of the resupply ship. Depending on ice conditions and weather, the water can stay open for several hundred yards or a few feet. The resupply ships at McMurdo are usually willing to hit a few chunks of ice in a trade off for safer following distances. The escorts usually take about 5 hours in a 20 mile channel.