Image caption The researchers looked at the ebb and flow of huge glaciers like this one in the Transantarctic Mountains as it enters the Ross Ice Shelf

The world's thickest ice sheet may be at greater risk from variations in the climate than previously believed.

Scientists found that glaciers on the East Antarctic Ice Sheet (EAIS) advance and retreat in synch with changes in temperature.

Since it contains enough water to raise global sea levels by over 50m, there is an urgent need to study the threat the researchers said.

The research has been published in the journal Nature.

Scientists have long been worried about the threat to sea levels from the prospect of melting in Greenland and in West Antarctica.

We are seeing a very sensitive reaction which we've never really seen before Dr Chris Stokes, Durham University

Greenland has had an annual loss of 140 billion tonnes over the past 20 years. Recent studies have indicated that Greenland will be much greener by 2100 thanks to global warming.

Researchers are also concerned about West Antarctica, where scientists have recently concluded that warming waters are causing a loss of ice from the shelf.

Image caption The image from 1963 is from declassified spy satellite imagery, with the end point of the glacier marked by a red line, where it enters the ocean. By 1990, the glacier has retreated from this position by around 3-4 km, but it subsequently re-advanced by 2000, before retreating again by 2010.

But most scientists have dismissed concerns over East Antarctica, the world's biggest ice sheet. Temperatures there can get down to minus 30C, meaning that it was essentially impervious to small, cyclical changes.

Now a new analysis questions that assumption.

Researchers at Durham University looked at declassified spy satellite imagery dating from 1963 to 2012. They used the pictures to detect changes in 175 glaciers as they flow into the sea along the 5,400km of coastline.

They found a strong pattern of ebb and flow. In the 1970s and 80s, when temperatures were rising they found that 63% of glaciers were retreating. During the 1990s, when temperatures decreased, 72% of the glaciers advanced.

"It is the first study to show that there is acute sensitivity in this particular ice sheet to climate variation," said Dr Chris Stokes who led the research.

"When we found these clear trends of advance and retreat, it was quite unexpected. But when we looked at the climate records it wasn't unexpected at all because they were just doing what the climate told them to do."

The researchers say that there is no immediate threat to global sea levels from their findings - but they are urging further investigation.

"People have thought because it is so big and so cold, it must be some way off a threshold of showing a reaction to climate but actually it is quite sensitive and we can see melt water ponds forming along the margin of this part of the ice sheet.

"In the next 100 years or so we could be looking at similar changes as we've seen in Greenland and West Antarctica.

"We are seeing a very sensitive reaction which we've never really seen before."

The scientists say there is no clear trend of warming in this part of Antarctica unlike the rest of the of world. The situation is complicated by the hole in the ozone layer that is changing wind directions and speeds.

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