Sydney - Sea ice stalled a planned helicopter rescue of passengers on a Russian ship trapped in frozen Antarctic seas on Thursday, despite improved weather conditions that had raised hopes the complex operation could proceed.
The Australian maritime safety authority had planned to begin an airlift of 52 passengers from the Akademik Shokalskiy after heavy rain and winds cleared at the site, 100 nautical miles east of the French base Dumont d'Urville.
The group, stranded in pack ice since 24 December, was to be flown to a nearby Chinese icebreaker Xue Long using its helicopter and transferred by barge to the more distant Australian resupply vessel Aurora Australis before leaving the Antarctic.
But the complex, multi-vessel operation hit a snag when the Aurora Australis's barge was unable to reach the Xue Long due to sea ice, forcing AMSA to call off the bid.
"It is now likely the rescue will not go ahead today," AMSA said.
"The Xue Long's helicopter is unable to land on the Aurora Australis due to load rating restrictions, and it is not safe to land the helicopter next to Aurora Australis at this time," it added.
"The preferred option is to wait for conditions that will allow the rescue to be completed in a single operation to reduce unnecessary risk."
AMSA said the "preferred and safest option at this stage is to ultimately transfer the passengers onto the Aurora Australis", and that alternative options were now being examined with the crews of the Australis and the Xue Long.
The Australian authority, which is co-ordinating the rescue, said it was a "complex operation" which was dependent on weather and ice conditions, both of which could change extremely rapidly.
"The priority is to ensure the safety of all involved", it said.
Groups of five
Expedition leader Chris Turney had been hopeful of a rescue on Thursday, posting a video about the improved weather conditions.
"A stunning day. Hopefully we'll hear about the evacuation soon", he said.
The helicopter operation follows several failed icebreaking attempts, with the Xue Long, Aurora Australis and French-flagged L'Astrolabe all forced to turn back by thick ice that they were unable to break through.
Outlining the aerial rescue plan earlier on Thursday, AMSA said passengers would be flown from the Akademik Shokalskiy in five groups of up to 12, with two extra flights to transfer luggage and equipment.
"Each return flight is expected to take about 45 minutes. The journey will cover a distance of about 12 nautical miles between the MV Akademik Shokalskiy and the Xue Long", AMSA said.
"The helicopter component of the rescue operation is expected to take at least five hours dependent on weather conditions", it said.
Although the ship is well provisioned and not in any immediate danger, the Russian crew who have had to spend Christmas and New Year marooned amid snow storms and blizzards are now preparing to wait until the ice breaks up.