Russia is preparing to launch an operation to rescue a group of scientists, after the sinking of their North Pole research base.
North Pole-32 marked Russia's return to polar research
The 12 researchers were unhurt, but equipment and supplies disappeared into freezing waters as the ice floe beneath the base collapsed late on Wednesday.
Efforts to drop emergency clothes, food and fuel have so far been hampered by strong winds.
North Pole-32 marked Russia's return to polar research after a 12-year absence.
The country was forced to suspend Arctic missions in 1991, when an ice floe carrying its 31st polar expedition was caught in a warm stream and broke up.
Wall of ice
The latest incident, which happened at 1715 Moscow time (1415 GMT) on Wednesday, destroyed 90% of the base's structures in half an hour.
"All of a sudden a huge wall of ice appeared that kept growing and growing," station chief Vladimir
Koshelyev told Russian media via telephone.
"First they were three meters high, then five, then
seven and finally over 10.
"Such a thing, I would say, has never before been seen on a polar station."
The team, who took refuge in two smaller buildings, have lost most of their fuel, leaving them with reserves to last for about five days.
A helicopter air-lift from the northern Russian port of Arkhangelsk is planned for Friday.
Strong winds of up to 50km/h threaten to delay take-off.
Rescuers say there is no need for panic yet - but the weather is expected to worsen at the weekend.
North Pole-32 was set up 10 months ago on floating Arctic ice to study climate change and assess mineral reserves.
It had almost completed its scientific mission when the disaster struck.
Earlier on Wednesday, 20 March was announced as its evacuation date.
The station's aircraft runway was ruined by melting ice, forcing supplies to be parachuted.
The floating station has covered a distance of 2,750km since it was set up last April. It has sent weather reports every six hours.
It is currently about 700km north-west of Norway's Spitzbergen archipelago.
A spokeswoman for the Russian hydrometeorology service told BBC News Online that the station had strayed too far to the south, hence the problems with melting ice.