Scientists say a crack along a key floating ice shelf in Antarctica indicates that a vast iceberg is close to breaking off.
The process, known as calving, happens periodically but researchers are watching closely to see whether climate change is affecting the phenomenon.
Scientists at the University of Swansea in Britain said Thursday the rift in the Larsen C ice shelf grew by 17 kilometers (10.6 miles) in six days.
They say the break, when it comes, could produce one of the largest icebergs ever recorded.
University of Colorado scientist Ted Scambos says the shelf appears to be breaking further back than previously recorded calvings.
Scambos adds that "this berg is telling us something has changed, and not for the better. For now, though, the ice shelf will barely notice."