This
is a wow revelation that mankind may well see revealed someday. The Greenland ice sheet is an excellent
candidate for almost complete melt out simply because it is the only remnant of
the Great Ice Age which effectively ended 12900 years ago with the singular
Pleistocene Nonconformity. The bulk of
the actual melt out was complete around 10,000 years ago and our resultant
climate we call the Holocene began to stabilize. Remnants continued plausibly through several
thousands of years ago.
Thus
this sheet is a remnant that is vulnerable to reduction on a far larger scale
than is obviously apparent. What is
more, a serious reduction is unlikely to be recovered. Thus a return of a sustained century’s long
warm period could well drive the sheet far back in long slow cycles that take
millennia to play out.
Mega-Canyon
Discovered Beneath Greenland Ice
August 29, 2013: Data from a
NASA airborne science mission has revealed an immense and previously unknown
canyon hidden under a mile of Greenland ice.
"One might assume that the landscape of the Earth has
been fully explored and mapped," said Jonathan Bamber, professor of
physical geography at the University of Bristol in the United Kingdom, and lead
author of the study published in today's issue of Science. "Our research shows there's still a lot
left to discover."
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.
This immense feature is thought to predate the ice sheet that has covered
Greenland for the last few million years.
The scientists used thousands of miles of airborne radar
data, collected by NASA and researchers from the United Kingdom and Germany
over several decades, to piece together the landscape lying beneath the
Greenland ice sheet.
A large portion of
this data was collected from 2009 through 2012 by NASA's Operation IceBridge,
an airborne science campaign that studies polar ice. One of IceBridge's
scientific instruments, the Multichannel Coherent Radar Depth Sounder, 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 Petermann Glacier fjord in northern Greenland.
At certain frequencies, radio waves can travel through the
ice and bounce off the bedrock underneath. The amount of times 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, IceBridge project
scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "It was
the enormous amount of data collected by IceBridge 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."
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.
"It is quite remarkable that a channel the size of the
Grand Canyon is discovered in the 21st century below the Greenland ice
sheet," said Studinger. "It shows how little we still know about the
bedrock below large continental ice sheets."
The IceBridge campaign will return to Greenland in March
2014 to continue collecting data on land and sea ice in the Arctic using a
suite of instruments that includes ice-penetrating radar.
Credits:
Production editor: Dr. Tony Phillips | Credit: Science@NASA
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