Parts of the east Antarctic ice sheet are thought to be particularly susceptible to climate change

Adelie penguins on an iceberg near Paulet Island at the tip of the Antarctica Peninsula. Photo / Tomas Munita via the New York Times

Landscapes left behind by ancient rivers and buried beneath the Antarctic ice may affect the rate of ice loss, researchers report in Nature Geoscience.

The team used radio echo sounding, a technique that measures ice thickness using radar, to study the east Antarctic ice sheet between Princess Elizabeth Land and George V Land in Antarctica.

Parts of the ice sheet are thought to be particularly susceptible to climate change because the land beneath it contains huge troughs that let warming ocean water reach the ice, causing rapid shrinking.

Radar measurements of the thickness elevation of the ice revealed a 2100 mile (3380km) stretch of previously undiscovered flat surfaces beneath the ice.

The surfaces had never been mapped.

The “coherent, pre-glacial surfaces” probably formed after the east Antarctic separated from the supercontinent of Gondwana, the researchers write.

The smoothness of the surface is consistent with it having been formed by ancient river systems that eroded the bedrock below.

The rougher surfaces beneath the ice sheet were probably shaped by ice itself, they write, which further eroded the landscape and carved deep troughs.

East Antarctica’s tectonic plate probably broke off of the supercontinent about 80 million years ago, with today’s ice sheet forming 34 million years ago.

Today, the researchers write, the flat surfaces probably “play a stabilising role” in parts of the ice sheet, while rapid melting is more likely to occur in the troughs.

The radar images of the region were covered in flat surfaces, study lead Guy Paxman, a Royal Society university research fellow in the geography department at Durham University, said in a news release.

“The flat surfaces we have found have managed to survive relatively intact for over 30 million years, indicating that parts of the ice sheet have preserved rather than eroded the landscape,” he added.

Further study of the ice sheet’s past could have “important implications for projections of future ice change and sea-level rise in a warming world,” the researchers conclude.