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.
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