Plans to rescue 52 passengers trapped on the stricken Russian research ship Akademik Shokalskiy have been thrown into disarray after the Chinese ice-breaker Xue Long itself became stuck in pack ice, west of the Mertz Glacier.
It is the second vessel to become trapped in the region in less than two weeks.
There were expectations that a helicopter on the Xue Long would today begin ferrying trapped passengers off the Russian ship.
UOW academic Ben Maddison and Illawarra scientist Chris Turney are on board the trapped Russian vessel.
The plan was for them to be transported by barge to the Aurora Australis.
However, alternative rescue plans are being considered after the captain of the Xue Long requested assistance when it became trapped.
Both the Xue Long and the Aurora need to be in open water to conduct the barge operation.
On Wednesday, the Aurora spent most of the day and evening ploughing towards the Chinese vessel, which has not moved under its own steam for more than a day, after it requested assistance.
While the Aurora made good, slow progress, coming within 2.1 nautical miles of the Chinese ship, by 1.30am on Thursday the Australian ice-breaker reached thick pack ice that it could not penetrate.
“Nature took over,” Aurora captain Murray Doyle said.
The Aurora is now drifting to the north-west with the surrounding pack ice, which moves with the wind and, to some extent, the current.
Since 7am, it has moved more than half a nautical mile to the north-west, thwarting ice-breaking attempts in the opposite direction.
The Xue Long was the first ice-breaker to reach the Akademik Shokalskiy, which has been stuck since Christmas Day. But the Chinese ship failed to get close when it attempted to break through the ice on December 27.
It is unlikely the Aurora will attempt to reach the Xue Long, which is on the other side of a pack fault line and so drifting in another direction.
The ship's captain Murray Doyle and voyage leader Leanne Millhouse, from the Australian Antarctic Division, are now weighing up alternative rescue plans.
The weather is clear with good visibility and a wind speed of about 22 knots.
The Australian Maritime Safety Authority’s Rescue Co-ordination Centre said it was now unlikely the rescue will go ahead today.
The Xue Long's helicopter is unable to land on the Aurora due to "load rating restrictions". It is also not safe to land the helicopter next to the Aurora.
All passengers on board the Russian ship are safe and well, the centre said.
"This rescue is a complex operation involving a number of steps. Operations in Antarctica are all weather and ice dependent and conditions can change rapidly," it said.
Nicky Phillips and Colin Cosier are travelling in Antarctica as part of the Australian Antarctic Division's media program.