SAN FRANCISCO (AP) -- The last U.S. icebreaker capable of crushing through the thickest ice of the Antarctic and Arctic resumed its mission after the latest repairs to postpone its already past-due retirement.
Climate change makes the 38-year-old Polar Star Icebreaker's science and security missions ever more vital, according to scientists and other backers of rebuilding the country's dwindling ice fleet.
The ship headed home to Seattle on Tuesday before starting its new assignment, said Coast Guard Spokeswoman Chief Warrant Officer Allyson Conroy.
Earlier Tuesday, crew members of the U.S. Coast Guard's Polar Star Icebreaker drilled before leaving the former naval shipyard at Mare Island, across the bay from San Francisco. Shipyard workers replaced worn, 18-foot-high propellers for refitting and carried out other work on the country's sole remaining heavy icebreaker, now eight years beyond its scheduled decommissioning date. The icebreaker is expected to head for Antarctica shortly after Thanksgiving.
By late January, the Polar Star will loom over the western Antarctic on its key annual mission - breaking through ice for the yearly resupply of U.S. researchers at the McMurdo Research Station and another research center at the South Pole.
With 75,000 horsepower and a hull strong enough to batter through six feet of ice at running speed, the Polar Star is the only operational U.S. vessel capable of getting the food, fuel and research material to the two Antarctic research stations.
If they 'didn't get that resupply, it would shut down or severely curtail the amount of science' at the two U.S. Antarctic centers, Capt. Matt Walker, the Polar Star's commander, said Monday afternoon from the Polar Star, with the icebreaker's gangway up for departure.
'It puts a huge weight of responsibility that we cannot fail, we cannot suffer catastrophic casualty to our equipment, because the resupply of McMurdo wouldn't occur,' Walker said. 'We have no redundancy in the U.S. system.'
Engine troubles in 2010 took the only other heavy U.S. icebreaker, the Polar Sea, out of service.
The U.S. Coast Guard has one other icebreaker, a medium-size one, which mainly works in the Arctic. The National Science Foundation has a still-lighter icebreaker for research. The Russian government, by contrast, has 18 icebreakers, including four, nuclear-powered and operational heavy icebreakers. Russia on Monday announced the planned start of work on a new icebreaker to supply that country's growing military presence in the Arctic and tug Russian combat ships through Arctic ice.
While the Obama administration, Congress and the Coast Guard all say maintaining at least one heavy icebreaker is essential for maintaining U.S. security and science, no funding proposals have yet gained momentum to have a new heavy U.S. icebreaker built before age forces the Polar Star out of service, any time from five to 20 years from now.
Without active heavy icebreakers, 'the control of the Arctic is in the hands of Russia,' California U.S. Rep. John Garamendi, the ranking Democrat on the House subcommittee that oversees the Coast Guard and maritime affairs, said Tuesday.
The Arctic is estimated to hold more than 10 percent of the world's undiscovered oil reserves, nearly one third of undiscovered gas reserves, and remains a strategically critical area for the United States, congressional researchers said earlier this year.
Melting ice means traffic has increased in the Bering Strait, between Russia and Alaska, 118 percent since 2008. More melting means more vessels will be coming within harm's way of ice.
Meanwhile, researchers say study of the 1.5 million-year-old ice of the Antarctic is critical to tracking the Earth's increasingly variable weather and the course of man-made climate change.
For American researchers, too, growing differences this year between the Russian and U.S. governments over Ukraine, Syria and other foreign-policy matters are increasing doubts about the Russia-U.S. logistical cooperation in science that bloomed after the Cold War seem more uncertain.
'The idea of sharing space stations or icebreakers with them - you feel a little less secure relying on them, because of the tensions, and the fact we're sort of poking each other in the eye lately,' said Ted Scambos, senior research scientist at the National Snow and Ice Data Center in Colorado and a veteran Antarctic researcher.
For Walker, the Polar Star's captain, each yearly run to the Antarctic is a run at unlocking critical secrets held in its ice.
'I think it's critical to humankind to be able to conduct the research work that they do in the Antarctic,' he said. 'It's fundamental to be able to predict or ascertain information about the climate change. The only place you can get that kind of information is Antarctica.'