By Steve Connor, Science Editor

It is one of the biggest in Antarctica and, for the past century, the massive Wilkins ice shelf appeared to have escaped the ravages of global warming. But now, enormous cracks have appeared in this floating ice platform the size of Northern Ireland. Scientists say it is breaking apart at an unprecedented rate after warmer temperatures weakened it.

A thin strip of ice is all that now prevents the Wilkins shelf from disintegrating and breaking away from the landmass of the Antarctic peninsula, scientists said yesterday. The peninsula is the fastest-warming region in the Antarctic and has seen some of the largest temperature rises on earth – 0.5C per decade – which is why the Wilkins ice shelf is on the verge of disappearing completely, said one of the scientists.

Observers at the British Antarctic Survey (BAS) in Cambridge and the US National Snow and Ice Data Centre in Colorado said they were astonished to discover just how fast the ice shelf was breaking apart since the first cracks were seen in February.

"Wilkins is the largest ice shelf yet on the Antarctic peninsula to be threatened, said David Vaughan of the BAS. "I didn't expect to see things happen this quickly. The ice shelf is hanging by a thread – we'll know in the next few days or weeks what its fate will be.

"In this case things are happening more rapidly than we thought. We didn't really understand how sensitive these ice shelves are to climate change," said Dr Vaughan, who predicted in the 1990s that it would take 30 years for the ice shelf to break up.

Several ice shelves on the peninsula have retreated in recent years and six of them – the Prince Gustav Channel, Larsen Inlet, Larsen A and Larsen B, the Wordie, Muller and the Jones ice shelves – have collapsed completely.

The Wilkins ice shelf is important because it is farther south on the Antarctic peninsula, where temperatures are generally colder than at the northern tip. "Climate warming in the Antarctic peninsula has pushed the limit of viability for ice shelves further south – setting some of them that used to be stable on a course of retreat and eventual loss," Dr Vaughan said.

"The Wilkins breakout won't have any effect on sea level because it is floating already, but it is another indication of the impact that climate change is having on the region."