Good News, Bad News On ‘Mega-Canyon’ Found Under Greenland Ice Sheet

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"Good News, Bad News On ‘Mega-Canyon’ Found Under Greenland Ice Sheet"

NASA data has revealed “an immense and previously unknown canyon hidden under a mile of Greenland ice.”

A 3-D view of Greenland's subglacial canyon. Via Bristol University.

A 3-D view of Greenland’s subglacial canyon. Via Bristol University.

Scientists pieced together this subglacial landscape using special ice-penetrating airborne radar data from NASA’s Operation IceBridge. How big is this “mega-canyon”?

The canyon has the characteristics of a winding river channel and is at least 460 miles (750 kilometers) long, making it longer than the Grand Canyon. In some places, it is as deep as 2,600 feet (800 meters), on scale with segments of the Grand Canyon.

The NASA news release also has an excellent video on the mega-canyon.

The mega-canyon has relevance today because it “extends from almost the center of the island and ends beneath the Petermann Glacier fjord in northern Greenland.”

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. 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. Climate Central explains, “as it nears the periphery, that water can affect the periphery of the ice sheet, particularly the shelves that stretch out into the ocean. There, ice has been slipping into the ocean and melting faster in recent decades.”

The calving Petermann ice shelf made news in 2010 (see “Greenland glacier calves the Arctic’s largest ice chunk in nearly a half-century”) — and last year, too, when an iceberg half as large calved (see “Glacial Change Ain’t What It Used To Be”).

The Petermann Glacier calving an ice island over twice the size of Manhattan in 2012.

The Petermann Glacier calving an ice island over twice the size of Manhattan in 2012.

Bristol University professor Jonathan Bamber is lead author of the study that appeared in the journal Science, “Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet.” Climate Central notes:

In 2008, researchers found channels in the bottom of the Petermann ice shelf, which weakened the ice and turned out to be harbingers of the events to come. Their findings suggested that warmer ocean water caused the channels. However, the new study suggests the mega canyon may be playing a role here as well.

“We argue that an important contribution to these undershelf channels is that there’s a large amount of subglacial channels,” Bamber said.

[Polar geophysicist Robin] Bell likened the process to beating eggs, where the water flowing down the canyon acts as a “whisk,” mixing up warmer ocean water under the ice shelf and deepening the cavities more rapidly.

As a major 2012 study found, Greenland ice sheet melt is up nearly fivefold since the mid-1990s. A study from July of this year found, “Surface meltwater draining through cracks in an ice sheet can warm the sheet from the inside, softening the ice and letting it flow faster.” That study pointed out that not only has the Greenland ice sheet accelerated at the edges where they flow into the ocean, but the “interior regions are also flowing much faster than they were in the winter of 2000-2001.”

So what’s the good news? Well, if humanity started sharply reversing emissions trends immediately, we could dramatically slow the disintegration of the Greenland ice sheet. Okay, that isn’t really news. How about this: If humanity stays anywhere near its current carbon pollution emissions path and Greenland goes largely ice free in the coming centuries as sea levels rise many tens of feet, then Greenland will have one truly eye-popping attraction for the well-heeled eco-tourist.

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