An iceberg that's 80 kilometres long is poised to break off Antarctica. 

Scientists say the rift has slowly been developing across the Antarctic Peninsula's Larsen C ice shelf for years, but it grew by 18 kilometres in December and now has only 20 kilometres left before it snaps off. 

Ice shelves are areas of ice floating on the sea, several hundred metres thick, at the end of glaciers.

The iceberg's 500-metre rift was recently caught on film by the British Antarctic Survey (BAS) as part the Melt on Ice Shelf Dynamics and Stability (MIDAS) project to monitor ice shelves and analyze the causes of changes in the region. 

The Larsen C ice shelf could shed an area of 5,000 square kilometres, MIDAS scientists said, which "will fundamentally change the landscape of the Antarctic Peninsula." 

Scientists are concerned that the loss of ice shelves will allow inland glaciers to slide faster towards the sea because of rising temperatures caused by global warming. 

Ice shelves had cracked in northern parts of the Antarctica recently, most notably the Larsen B ice shelf, which disintegrated in 2002. 

Should this break off, it will be the largest ever recorded.

With files from Reuters