'Grand Canyon' of Greenland Discovered Under Ice
J. Bamber, University Bristol
3D view of the subglacial canyon, looking northwest from central Greenland.
Spring's not all about pretty flowers and greening trees. For some scientists it means watching Arctic ice. Scientists and engineers with NASA's Operation IceBridge are already at it, surveying glaciers in Greenland, Alaska and northern Canada. The flight part of the largest aerial survey of Earth's polar ice ever flown – a six-year mission over both poles aimed at producing a three-dimensional view of Arctic and Antarctic ice sheets, ice shelves and their sea ice.
Here, NASA's P-3B sits on the tarmac of the Kangerlussuaq Airport. The plane is equipped with a suite of instruments that gather data as the plane flies over the ice. It also carries scientists and teachers, some of whom took the following images.
The glacial Alaskan mountains are seen from high altitude aboard the P-3B during the IceBridge flight from Thule, Greenland, to Fairbanks, Alaska, on March 21, 2013.
A true river of ice, or glacier, on Greenland's Geikie Peninsula.
Tongue-shaped moraines appear to lick at the Penny Ice Cap on Baffin Island, Nunavut, Canada. These moraines are debris that was plowed up and left behind by past glaciers
Another moraine left by a small glacier on Penny Ice Cap on Baffin Island, Nunavut, Canada.
This year's aerial survey of the Penny Ice Cap glacier follows previous radar surveys done in 1995, 2000 and 2005 using the Airborne Topographic Mapper and CReSIS radar instrument.
Near Thule Air Base, sled dogs rest on the sea ice in North Star Bay. Behind them is the 700-foot-high Mount Dundas. Cities in Greenland are connected by ship and air, but shorter distances are crossed by snowmobile or dogsleds.
No, not another glacier, but an ice-covered fjord on Baffin Island near Davis Strait, which is in the distance. Baffin Island is the fifth largest island in the world.
This is a mosaic image of sea ice in the Beaufort Sea. The darkest zone is open water. Light blue zones are thick sea ice, while dark blue zones are thinner ice. The image was created by the Digital Mapping System (DMS) instrument aboard the IceBridge P-3B.
Icebergs crowd the sea ice of Jakobshavn Fjord, seen from NASA’s P-3B aircraft on the Apr. 4, 2013, IceBridge survey. Jakobshavn Glacier produces one in ten Greenland icebergs and is one of the fastest moving ice streams in the world.
NASA / DMS
Another view of the cracked Beaufort Sea ice by the Digital Mapping System (DMS) instrument aboard the IceBridge P-3B. The DMS uses a camera that points down through a window in the underside of the plane. It snaps a frame each second which are combined into a mosaic.
On April 8, 2013, science teacher Mark Buesing of Libertyville High School in Libertyville, Ill., shoots Greenland glaciers through the window of NASA's P-3B.
Eastern Greenland's Helheim Fjord is surveyed on April 5, 2013, from the NASA P-3B. Helheim is one of the largest in Greenland.
The P-3B sees its shadow on April 9, 2013, on the sea ice southeast of Greenland. Flying low altitude is all part of gathering detailed ice data.
Danish high school science teacher Jette Rygaard Poulsen watches the Greenland ice roll by from a window of the P-3B airborne laboratory on Apr. 8, 2013.
Not everything is icy in Greenland. Even as early as April 8, southwestern Greenland has ice free fjords.
An actively calving glacier front on the ocean in southwestern Greenland on April 8.
In two plots of topographic data from the Jakobshavn Glacier warmer colors are higher ice elevation. The calving front is at the transition from warm to cool colors. The difference between the two dates of survey reveal a loss of about 200 meters of ice.
It doesn't affect the ice, but there are some other interesting sights in Greenland this spring, like the aurora borealis over Kangerlussuaq.
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 this week 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," Bamber told LiveScience's OurAmazingPlanet. (See Photos of Mega-Canyon Under Greenland Ice Sheet)
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
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. (North vs. South Poles: 10 Wild Differences)
"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.
"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. (Fly Over Greenland's Grand Canyon)
A topographic map of Greenland from bedrock elevation data.J. Bamber, University Bristol
Where the water flows
Scientists still have very little insight into how much water flows under the middle of Greenland's Ice Sheet, or where it goes, because of how hard it is to reach the thick ice, then drill under it or measure a thin film of water with radar. Yet understanding the water flow is an important part of predicting how the ice sheet will behave as the climate warms. The uncertainty means conflicting models of water movement, called basal hydrology, are often published in research journals within weeks of each other.
"When it comes to basal hydrology under the big ice sheets, we are basically scratching our heads at this point," said Michael Studinger, project scientist for NASA's Operation IceBridge, who was not involved in the study. "That's why you see contrasting results coming out." (IceBridge is a mission that uses airplanes outfitted with various instruments to measure changes in the polar ice sheets every year.)
The canyon predates the ice sheet that permanently covered Greenland about 1.8 million years ago, Siegert said. The channel curls across northwestern Greenland, ending in a deep fjord filled by Petermann Glacier. The find opens a whole new set of ideas to explore for scientists studying the glacier's rapid retreat.
"If there is a channel that can transport subglacial meltwater all the way from the interior of Greenland to the coast, that flows right into Petermann Glacier, you change the whole water circulation there and have a big impact on stability," Studinger said in an interview. "This is one of the biggest glaciers in Greenland and it produces a lot of big icebergs," he said.
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.'"
Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook & Google+. Original article on LiveScience's OurAmazingPlanet.
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