The ice will add to risks for ships now it has broken off.

The peninsula is outside major trade routes but is the main destination for cruise ships visiting from South America.

In 2009, more than 150 passengers and crew were evacuated after the MTV Explorer sank after striking an iceberg off the Antarctic peninsula.

The iceberg, which is likely to be named A68, was already floating before it broke away so there is no immediate impact on sea levels, but the calving has left the Larsen C ice shelf reduced in area by more than 12 per cent.

The Larsen A and B ice shelves, which were situated further north on the Antarctic Peninsula, collapsed in 1995 and 2002, respectively.

“This resulted in the dramatic acceleration of the glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise,” said David Vaughan, glaciologist and director of science at British Antarctic Survey.

“If Larsen C now starts to retreat significantly and eventually collapses, then we will see another contribution to sea level rise,” he added. Big icebergs break off Antarctica naturally, meaning scientists are not linking the rift to manmade climate change.

The ice, however, is a part of the Antarctic peninsula that has warmed quickly in recent decades.

“In the ensuing months and years, the ice shelf could either gradually regrow, or may suffer further calving events which may eventually lead to collapse — opinions in the scientific community are divided,” Professor Luckman said.

“Our models say it will be less stable, but any future collapse remains years or decades away.”