longest canyon in the world- Tan Shang Jien

‘Grand Canyon’ of Greenland Discovered Under Ice Sheet

Greenland's longest canyon

The age of discovery isn’t over yet. A colossal canyon, the longest on Earth, has just been found under Greenland’s ice sheet, scientists announced today (Aug. 29) in the journal Science.

“You think that everything that could be known about the land surface is known, but it’s not,” said Jonathan Bamber, lead study author and a geographer at the University of Bristol in the United Kingdom. “There’s still so much to learn about the planet.”

The great gorge meanders northward from Summit, the highest point in central Greenland, toward Petermann Glacier on the northwest coast, covering more than 460 miles (750 kilometers). Researchers think the ravine could be even longer, but they don’t yet have the data to prove where the canyon peters out deep under the interior ice sheet. “It may actually go farther south,” 

The broad chasm is up to 2,600 feet (800 meters) deep and 6 miles (10 km) wide, similar to America’s Grand Canyon in scale, the researchers said. The distinctive V-shaped walls and flat bottom suggests water carved the buried valley, not ice, Bamber said. Though it is not the

world’s deepest canyon, it’s the longest, handily besting the 308-mile-long (496 km) Yarlung Tsangpo Grand Canyon in China.

Many mysteries in what lies beneath

Greenland topography

The discovery could raise as many questions as it answers. For instance, researchers have long puzzled over what happens to water under Greenland’s interior ice sheet. Greenland bows inward like a soup bowl, yet water melting under the interior ice sheet seems to drain to the sea instead of pooling in the middle. Bamber and his colleagues think the northern canyon may route some of the meltwater into the ocean.

The great river channel could explain the missing lakes under Greenland’s interior ice sheet. The weight of the ice sheet pushes down the island’s middle into a bowl-shaped basin. Given this saggy middle, scientists have long wondered why Greenland isn’t filled with buried lakes, like Antarctica’s Lake Vostok and Lake Whillans. The northern part of the canyon may drain meltwater, but farther inland, Bamber and his colleagues think the massive weight of ice pushes water elsewhere.

“It probably doesn’t have water flowing through all of it today, given the interference by the ice overburden. However, when ice-free, water would channel through all of it,” Siegert told LiveScience’s OurAmazingPlanet.

And the newly discovered canyon could boost the breakup of one of the coastline’s briskly retreating glaciers. The Greenland Grand Canyon dumps right into Petermann Glacier, which has dropped two massive icebergs in the past three years, each bigger than Manhattan.

A Greenland iceberg called PII-2012 is moving toward the Nares Strait.

“It’s fair to say that a lot of work is now needed to work out the evolution of this feature and what it means for today’s ice sheet,” said study co-author Martin Siegert, a glaciologist at the University of Bristol. 

The new canyon isn’t the first amazing polar discovery from Bamber and his colleagues, who are experts in creating models of the polar regions, but it is one of the most incredible, they say. Siegert compared it to learning of Lake Vostok in Antarctica. “When Jonathan came into my office and put [the] papers on my desk, it was a jaw-dropping experience,” Siegert said.

The gorge popped out of airborne radar data collected by NASA’s Operation IceBridge and many other Arctic surveys. The radar onboard the IceBridge plane penetrates the ice, revealing the landscape below. Hints of a linear feature in northwest Greenland had appeared in earlier bedrock maps, but no one ever had enough detail to find the canyon until now, Bamber said.

“It wasn’t exactly a ‘Eureka’ moment, but as we worked up the data, we realized there was something there that looked pretty extensive,” Bamber said. “We looked at some profiles across it just to make sure it was what we thought it was, and it very much looked like a river profile,” he said. “I thought, ‘Well, crikey, we’ve discovered a 500-mile-long paleoriver.'”

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