Grand Canyon (Greenland)

Animation of the canyon

Topographic map of the bedrock under the ice

Greenland's Grand Canyon or Grand Canyon of Greenland is a tentative name for the canyon of record length discovered underneath the Greenland ice sheet as reported in the journal Science on 30 August 2013 (submitted 29 April 2013), by scientists from the University of Bristol, University of Calgary, and University of Urbino, who described it as a mega-canyon.

Ice-penetrating radar data collected during NASA's Operation IceBridge showed a huge subglacial canyon running from the central region of the island northward into the Arctic Ocean, to the fjord of the Petermann Glacier. The canyon is likely to have influenced basal water flow from the ice sheet interior to the margin. Jonathan Bamber, a geographer at University of Bristol, stated, "The distinctive V-shaped walls and flat bottom suggests water carved the buried valley, not ice."

The canyon is more than 750 kilometres (466 mi) long, up to 800 metres (2,600 ft) deep and 10 kilometres (6 mi) wide, making it the longest canyon discovered on the Earth to date. There are, however, many canyons—including Arizona's Grand Canyon and Xizang's Yarlung Tsangpo Grand Canyon, previously the world's longest—which are deeper.

The canyon predates ice sheet inception and has influenced basal hydrology in Greenland over past glacial cycles. It is estimated to be at least four million years old, possibly millions of years older.

The mega-canyon has relevance today because it “extends from almost the center of the island and ends beneath the Peterman Glacier found in northern Greenland. The researchers believe the canyon plays an important role in transporting sub-glacial melt water from the interior of Greenland to the edge of the ice sheet into the ocean. Evidence suggests that before the presence of the ice sheet, as much as 4 million years ago, water flowed in the canyon from the interior to the coast and was a major river system. So the mega-canyon is a channel for water to travel from Greenland’s interior to the sea. A large portion of this data was collected from 2009 through 2012 by NASA's Operation Ice Bridge, an airborne science campaign that studies polar ice. One of Ice Bridge’s scientific instruments, the Multichannel Coherent Radar Depth Sounder, operated by the Center for the Remote Sensing of Ice Sheets at the University of Kansas, can see through vast layers of ice to measure its thickness and the shape of bedrock below. In their analysis of the radar data, the team discovered a continuous bedrock canyon that extends from almost the center of the island and ends beneath the Peterman Glacier fjord in northern Greenland. At certain frequencies, radio waves can travel through the ice and bounce off the bedrock underneath. The time the radio waves took to bounce back helped researchers determine the depth of the canyon. The longer it took, the deeper the bedrock feature. "Two things helped lead to this discovery," said Michael Studinger, Ice Bridge project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "It was the enormous amount of data collected by Ice Bridge and the work of combining it with other datasets into a Greenland-wide compilation of all existing data that makes this feature appear in front of our eyes."