A shift in Antarctic weather around the polar ships Akademik Shokalskiy and Xue Long has let them break free of heavy ice that trapped them.
Cracks began to appear late on Tuesday around the Shokalskiy, and cleared the heaviest ice about 11pm (NZT), according to the Australian Maritime Safety Authority.
The Russian tourist expedition ship had begun to make slow progress north through lighter ice conditions two weeks after it was trapped, forcing AMSA to launch a rescue mission.
Yury Volgov, director of the Far-Eastern Hydrometeorology Research Institute, which owns the Academician Shokalsky, told Russian media the situation was now favourable.
"First, the wind changed direction from an Easterly to a North-Westerly, which changed the direction of ice drift. A large crack formed in the ice, and the ship is now navigating it," Mr Volgov, told Russia Today.
The Chinese Government polar expedition ship Xue Long, which went to the aid of the Shokalskiy, had been waiting for the wind change to attempt to free itself.
Xue Long's captain told AMSA on Tuesday night that it too had managed to break free of the heavy ice, was making slow progress through lighter conditions and did not require further aid.
The Chinese Xinhua news agency said on Wednesday it had reached open water.
AMSA's Rescue Co-ordination Centre said it had asked both vessels to advise once clear of the ice field.
"RCC Australia is awaiting confirmation that (Shokalskiy) does not require any further assistance," AMSA said.
Meanwhile, it said, the US Coast Guard's heavy icebreaker Polar Star will continue heading south from Sydney towards the incident at Commonwealth Bay, until it is clear that both vessels are free of the ice field and no longer in danger.
Overnight the Australian ship, Aurora Australis, arrived at Casey station to resume a resupply mission interrupted to rescue the 52 passengers aboard the Shokalskiy.
The group would remain aboard the ship during the resupply, and were expected back in Hobart on Aurora around January 22, the Australian Antarctic Division said.
The division's director, Tony Fleming, said the rescue had put the division around two weeks behind in its shipping schedule, and would mean delays for the rest of the season.
- Sydney Morning Herald
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