Al Sutherland, ocean projects manager in NSF's Office of Polar Programs, said the ice extends almost three times farther out from the station than is usual.

Normally, the ice edge -- the place where the ice in McMurdo Sound meets open water -- would be found about 15 miles from McMurdo Station. Currently, Sutherland said, the ice edge is nearly 40 miles out. He added that very dense "pack ice" stretches roughly 200 miles from the station to iceberg C-19, which broke away from the Ross Ice Shelf in May.

The U.S. Coast Guard vessel Healy, an icebreaker with design features for supporting Polar science, particularly in the Arctic, left its home port of Seattle on Jan. 9th, to sail south for roughly 27 days to join the Coast Guard icebreaker Polar Sea, which already is working in McMurdo Sound.

Healy recently conducted a very productive science season in the Arctic, notably in support of the NSF-supported Western Shelf-Basins Interactions (SBI) project, which is looking for early indicators of climate change in the Arctic Ocean. Researchers on a previous Healy cruise found evidence that the Arctic's Gakkel Ridge, the world's slowest spreading mid-ocean ridge, may have substantial volcanic activity.

NSF concurred with a Coast Guard recommendation to send Healy to assist in icebreaking operations. Coast Guard officials have assured NSF that Healy's Antarctic deployment will not affect planned Arctic research. It is possible that Healy could be recalled if conditions do not warrant its prolonged presence in Antarctica.

A freighter and a fuel tanker annually provide a lifeline that allows the U.S Antarctic Program to conduct science on the southernmost continent.

The icebreakers' primary tasks are to open a channel from the ice edge to McMurdo Station and to ensure that the supply ships safely navigate the narrow channel in and out of the station.

Normally, a single icebreaker, either the Polar Sea or its sister ship, the Polar Star, is sufficient to break a channel into the station and to escort the supply vessels in and out.

Last year extensive sea ice conditions required that the Polar Sea and Polar Star be sent south together. The two ships were successful in getting the other vessels safely in and out. Sea ice was extensive around the continent and the conditions specific to McMurdo Sound may also have been affected by the presence of an enormous iceberg, designated B-15.

This year, sea ice is again extensive in the McMurdo Sound area and the adjacent Ross Sea. B-15 remains in the same position near McMurdo. C-19, has grounded in the Ross Sea and may be contributing to this extensive ice.

Because Polar Star is undergoing substantial maintenance and is unable to steam south, Healy is being deployed to help Polar Sea meet two challenges, Sutherland explained.

The first is to break a channel through the ice to Hut Point at McMurdo Station and to keep it open. Although the Polar Sea already has broken a channel into the McMurdo Sound as far south as Hut Point, the ice conditions are so severe that one ship, in the time available, might not be able to prepare the channel and escort the re-supply ships through the heavy pack ice without the assistance of the second icebreaker.

The second challenge is to escort the supply ship American Tern and the fuel tanker MV Richard G Matthiesen into McMurdo to prepare the station for the long austral winter.

When escorting other ships, Sutherland said, the icebreakers serve to push aside -- or shed -- the ice that constantly threatens to fill in the narrow channel.

"The freighter and the tanker are ice-strengthened, but they are not icebreakers," Sutherland said. "If they have an icebreaker immediately in front of them � they have to stay almost bow to stern � the icebreaker is essentially shedding all the ice."

Although it is a multipurpose icebreaker, Healy was designed with the primary mission of supporting Arctic science. Healy is equipped with engines that produce roughly half the peak power of the Polar Sea. But NSF and Coast Guard officials are confident that Healy, which was commissioned in 1999, will operate effectively in Antarctica.

Under an agreement with NSF, the Coast Guard provides icebreaking services to the U.S. Antarctic Program. The additional cost to NSF to deploy Healy to Antarctica will be roughly $1.2 million. Additional fuel also will be needed at McMurdo Station to keep both ships running.

Related Links
Healy And The Polar Icebreakers
Iceberg C-19
National Science Foundation
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