Mountain ranges and valleys hundreds of miles long are hidden deep beneath Western Antarctica’s vast ice region, a discovery that scientists say shows Antarctica could contribute even more to rising global sea levels.

A team of researchers used ice-penetrating radar to map the subglacial landscape, which they say adds a key piece of evidence for understanding the frozen continent. The researchers discovered three valleys linking two major ice regions: the Western Antarctic Ice Sheet and the far bigger Eastern Antarctic Ice Sheet.

The newly discovered land forms prevent ice from East Antarctica from flowing through West Antarctica and to the coast. But as ice sheets thin because of warming temperatures, these valleys and mountain ranges could “increase the speed and rate at which ice flows out from the center of Antarctica to its edges, leading to an increase in global sea levels,” said Kate Winter, the study’s lead author and a research fellow at Northumbria University.

“Understanding how the East and West Antarctica ice sheets interact is fundamental to our understanding of past, present and future global sea level,” said Neil Ross, a senior lecturer at Newcastle University.

The biggest of the valleys, called Foundation Trough, is 217 miles long, nearly equal to the distance between Washington, D.C., and New York City. Its width is more than 20 miles.

The other valley, called Patuxent Trough, is nearly 200 miles long and nine miles wide. The smallest, the Offset Rift Basin, is 93 miles long and 18 miles wide.

The research was part of the European Space Agency’s PolarGAP project, an ambitious mission to collect data about the Earth’s global gravity field, and was published earlier this month in the Geophysical Research Letters journal.

Fausto Ferraccioli, principal investigator of the PolarGAP project, said the findings provide an important window into the South Pole region, “one of the least understood frontiers in the whole of Antarctica.”

“These new PolarGAP data gives us both insights into how the landscape beneath the ice influences present ice flow, and a better understanding of how the parts of the great Antarctic ice sheets near the South Pole can, and cannot, evolve in response to glaciological change around their margins,” Ferraccioli said.

The discovery was a surprise to researchers.

Winter told NBC News that they had expected to find a mountainous region, but they were not expecting the enormous size of the land forms.

Research has shown that Antarctica’s coastal glaciers, particularly in West Antarctica, are retreating at an alarming rate, raising concerns about the massive continent’s potential contribution to rising sea levels.

Last month, a new satellite survey revealed that 10 percent of Antarctica’s coastal glaciers are moving at a significant speed back toward the center of the continent as they melt below, The Washington Post’s Chris Mooney reported. In West Antarctica, more than 20 percent of coastal glaciers were retreating faster than 25 meters, or 82 feet, per year. The situation isn’t as bad in East Antarctica, although the area’s largest glacier is also retreating at a fast rate.

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