A canyon at least 750km (460 miles) long with depths of up to 800 metres (2,600 feet) has been lurking 1.6km (1 mile) beneath an ice sheet that blankets Greenland, data from an airborne science mission has revealed.
The canyon has the characteristics of a winding river channel and is longer than the Grand Canyon in Arizona, US space agency NASA said, adding that the canyon is thought to predate the ice sheet that has covered Greenland for the last few million years.
“One might assume that the landscape of the Earth has been fully explored and mapped,” said Jonathan Bamber, professor of physical geography at the University of Bristol in the United Kingdom, and lead author of the study. “Our research shows there’s still a lot left to discover.”
The research has been published in the journal Science.
The scientists mapped out the canyon by using thousands of kilometres of airborne radar data that NASA and researchers from the UK and Germany have collected over several decades.
NASA’s Operation IceBridge collected a large portion of this data between 2009 and 2012.
In their analysis of the radar data, the scientists discovered a continuous bedrock canyon that extends from almost the centre of the island and ends beneath the Petermann Glacier fjord in northern Greenland.
At certain frequencies, radio waves can travel through the ice and bounce off the bedrock underneath. The amount of times the radio waves took to bounce back helped researchers determine the depth of the canyon. The longer it took, the deeper the bedrock feature, NASA said.
The researchers believe the canyon plays an important role in transporting sub-glacial meltwater from the interior of Greenland to the edge of the ice sheet into the ocean. NASA said evidence suggests that before the presence of the ice sheet, as much as 4m years ago, water flowed in the canyon from the interior to the coast and was a major river system.