An iceberg the size of Norfolk is poised to break away from a vast ice shelf in the north-west area of Antarctica.
Only a threadlike sliver 12 miles wide is keeping the 1,900sq-mile chunk attached to the Larsen C ice shelf in the Weddell Sea.
Professor Adrian Luckman of Swansea University told the BBC: "If it doesn't go in the next few months, I'll be amazed."
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When it eventually breaks away, a process known as calving, the iceberg is predicted to be one of the top ten largest ever on record.
A massive crack in the 1150ft-thick ice shelf first appeared decades ago, says the BBC, "but in December the speed of the rift went into overdrive, growing by a further 18km [11 miles] in just a couple of weeks".
A Nasa photograph of the fracture shows it measures around 70 miles long, is 300ft wide and runs a third of a mile deep.
Larsen C was the largest of three adjoining ice shelves, until Larsen A and B both broke up in 1995 and 2002 respectively. Larsen B "disintegrated" after developing a similar rift, Nasa says.
The collapse of the millennia-old shelves was partially attributed to the effects of climate change, as warmer waters lapped away at the edges of the ice.
Ice shelves act as a barrier between the glaciers which flow off of the Antarctic mainland and the open sea. If the last intact section of the Larsen ice shelf were to disintegrate, leaving the glaciers to float away from the polar continent, scientists estimate global sea levels would rise by 4ins.
However, any future collapse of Larsen C is likely to be well into the future, say researchers.
"We would expect in the ensuing months to years further calving events and maybe an eventual collapse," Professor Luckman said. "But it's a very hard thing to predict and our models say it will be less stable, not that it will immediately collapse or anything like that."
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