Researchers have found the ice sheet has “passed the point of no return”. Photo: Stuart Dunning/PA Wire

The loss of ice in Antarctica caused by a warming ocean could raise global sea levels by three metres, according to researchers.

Scientists have been carrying out fieldwork in the region to assess the landscape and determine how the West Antarctic ice sheet might respond to increasing global temperatures.

They described their findings as “troubling” and said it is possible the ice sheet has “passed the point of no return”.

The study – said to be the first of its kind – was carried out by scientists at the University of Edinburgh, Northumbria University and the Scottish Universities Environmental Research Centre.

Researchers were able to gauge how levels of ice covering the land have changed over hundreds of thousands of years by studying peaks protruding through ice in the Ellsworth Mountains on the Atlantic flank of Antarctica.

The team assessed changes on slopes at various heights on the mountainside which indicate levels previously reached by the ice sheet.

They also mapped the distribution of boulders on the mountainside, which were deposited by melting glaciers. Chemical technology, known as exposure dating, showed how long rocks had been exposed to the atmosphere and their age.

The study found that parts of the West Antarctic ice sheet have existed continuously for at least 1.4 million years.

But the results also indicate that during previous warm periods, a substantial amount of ice would have been lost from the sheet by ocean melting, although it would not have melted entirely.

This suggests that ice would have been lost from areas below sea level, but not on upland areas, researchers said.

Joint study leader Andrew Hein, of Edinburgh University’s School of GeoSciences, said: “Our findings narrow the margin of uncertainty around the likely impact of the West Antarctic ice sheet on sea level rise.

“This remains a troubling forecast since all signs suggest the ice from West Antarctica could disappear relatively quickly.”

John Woodward, professor at the University of Northumbria, who also co-led the study, said: “It is possible that the ice sheet has passed the point of no return and, if so, the big question is how much will go and how much will sea levels rise.”

The study, supported by the Natural Environment Research Council and the British Antarctic Survey, is published in the journal Nature Communications.