Scientists reported last week that they have discovered a vast canyon buried deep beneath the ice sheet that covers Greenland, the world’s largest island.

The canyon runs from the centre of Greenland to its northern coast on the Arctic Ocean, some 740 kilometres away. The gouge is about 50 percent longer than the Grand Canyon in the US and ranges from 200 to 800 metres deep. It has most likely been covered by ice for four million years.

Part of an ancient river system
Glaciologist Jonathan Bamber from the University of Bristol in the UK and other researchers from universities in Canada and Italy examined data compiled by NASA research planes that have flown over Greenland for the past 40 years to peek at what lies below the ice.

"We started looking at the data, and once we put it all together, we realised there was this strange feature in the middle of Greenland," Bamber told the journal Science. 

Bamber said that the researchers believe the canyon was carved by a major river system before Greenland was covered in ice.

Climate change research leads to discovery
The discovery is a result of the increased scientific focus on Greenland in studying the effects of climate change. The radar images were shot by NASA’s Operation IceBridge, which flies aircraft over the island because the ice sheet is too thick for satellite-based radar to penetrate.

"It really shows how little we know about what's below the major continental ice sheets, like the Greenland ice sheet and the Antarctic ice sheet," IceBridge’s lead scientist, Michael Studinger, told Science.

In addition to its depth below the ice, another reason that the canyon has gone undetected for so long is that scientists studying ice sheets tend to focus their attention on the coastlines and the effect that the crumbling ice has on sea level.

A NASA video about the discovery is viewable below.