The Polar Star, the Coast Guard's only active heavy polar ice breaker, was being sent to help free the Russian and Chinese vessels from thick bands of ice, officials said.
According to a Coast Guard statement, the Polar Star left its home port of Seattle in early December on one of its primary missions, Operation Deep Freeze. The mission involves breaking a channel through the sea ice of McMurdo Sound to resupply and refuel the U.S. Antarctic Program's McMurdo Station on Ross Island.
"Our highest priority is safety of life at sea, which is why we are assisting in breaking a navigational path for both of these vessels," said Vice Adm. Paul F. Zukunft, the Coast Guard Pacific Area commander. "We are always ready and duty-bound to render assistance in one of the most remote and harsh environments on the face of the globe."
Zukunft said 52 scientists and tourists who had been trapped for a week aboard the Russian vessel, the Akademik Shokalskiy, had been airlifted to safety Thursday by helicopter from the second stranded ship, the Chinese vessel Xue Long, or Snow Dragon.
The scientists and tourists were taken to an Australian icebreaker called the Aurora Australis, which is expected to transport them to Tasmania in mid-January. The 22 crew members stayed with the vessel, which was not in danger of sinking and had enough supplies to last weeks.
A Chinese reporter aboard the Xue Long said Saturday that an iceberg had appeared overnight and was blocking the ship's passage. The 101 crew members aboard the ship were described as safe and fully supplied.
The Polar Star was responding to a request from the Australian Maritime Safety Authority, coordinator for the ongoing rescue operations.
The National Science Foundation manages the U.S. Antarctic Program, which coordinates all science research and related logistics in Antarctica and on the Southern Ocean. McMurdo Station is the logistics hub for NSF's research.
For more than 50 years, Coast Guard icebreaker crews have deployed to Antarctica in support of Operation Deep Freeze, U.S. officials said. Before being cut short to help in the rescue mission, the cutter was deployed to help create a navigable shipping lane through the layers of sea ice in McMurdo Sound and permit the delivery of critical fuel and supplies to run the U.S. McMurdo and South Pole stations throughout the coming year.