Sunday, March 6, 2011

New information on antarctic from the journal SCIENCE>

 For full story and video links, please use link below:
Link to MSNBC Web site.

This satellite view shows Antarctica, which is covered by
two ice sheets divided by the Transnatarctic Mountains.
A new studyfound that a plateau justeast of the
mountain range includes ice that thaws and freezes over
time, changing the structure of the ice sheet.

By Miguel LlanosReporter
updated 3/3/2011 3:15:55 PM ET
Knowing how the massive ice sheets atop
Antarctica and Greenland work is key to
predicting how global warming could raise sea
levels and flood coastal cities. But a new study
upends what scientists thought they knew. It
turns out it’s not just ancient snow that makes
up the ice sheets, but water deep under the
sheets also thaws and refreezes over time.

To put it in non-scientific terms, lead scientist
Robin Bell told, the study
redefines "how squishy" the base of ice sheets
can be. "This matters to how fast ice will flow
and how fast ice sheets will change."

"It also means that ice sheet models are not
correct," she said, comparing it to "trying to
figure out how a car will drive but forgetting to
add the tires. The performance will be very
different if you are driving on the rims."

Reporting in this week's issue of the peer-
reviewed journal Science, Bell and his team
described how ice-penetrating radar peeled
back two miles of ice a million years old in the
center of
The images show that refrozen ice makes up
24 percent of an area known as Dome A, a
13,800-foot-high plateau roughly the size of
California. Much of the sheet and refrozen ice
lies atop an underground mountain range.

Ice from that area "drains into all the major ice
shelves of Antarctica," the researchers wrote
in their study. "Processes occurring in the
'Squishy' ice shifts climate models, study says
Ice sheet structure far different than thought — complicating rising-sea scenarios
Dome A region have the potential to affect the
majority of East Antarctica."

While the field work was far inland, Bell
believes the same will hold true along the
edges of the icy continent. "We believe there is
this ice rimming the ice sheets at the edge so
this will impact how they will change," said
Bell, a geophysicist at Columbia University's

The Antarctic ice sheets, some of it more than
two miles thick, holds enough fresh water to
raise ocean levels 200 feet if it all melted.
That's not expected but even if a small part did
melt it could threaten millions of coastal
dwellers worldwide.

Given already known melt in Greenland and
parts of Antarctica, the U.N. Intergovernmental
Panel on Climate Change earlier estimated
will rise between seven inches and two
feet this century.

Bell said the study did not look at what kind
of impact the refreezing would have. "We are
not sure if it will make them go faster or
slower," he said of ice sheets flowing into the
ocean and thus raising sea levels.

How can water be sandwiched between the ice
sheet and the continent?

"Deeply buried ice may melt because overlying
layers insulate the base, hemming in heat
created there by friction, or radiating naturally
from underlying rock," Columbia University
said in a statement along with the study.
"When the ice melts, refreezing may take place
in multiple ways ... If it collects along mountain
ridges and heads of valleys, where the ice is
lowtemperatures penetrating from the
surface may refreeze it. In other cases, water
gets squeezed up valley walls, and changes
pressure rapidly.

"In the depths, water remains liquid even when
it is below the normal freezing point, due to
pressure exerted on it. But once moved up to
an area of less pressure, such supercooled
water can freeze almost instantly."

Ted Scambos, lead scientist at the National
Snow and Ice Data Center in Boulder, Colo.,
told that the finding was
"unexpected in its scope" but he also felt it

Robin Bell
This radar image shows part of the East Antarctic ice sheet (top), a bulge of refrozen ice (center), and the profile of a mountain range buried deep below (outlined in red).
would be limited to the interior of East
Antarctica, not the more vulnerable coastlines.

"I think it is an astounding discovery," added
Scambos, who was not involved with the
study. "Who knew that a buried mountain
range would let you grow the ice sheet from

Bell said that "the important message" is that
while ice experts have long known of
underground water systems "greasing the
bottom of ice sheets," and thus potentially
undermining them, "we never considered that
they might be important for the actual
structure of the ice sheet."

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