[Vision2020] JPL: Cal-Tech: Antarctic Ice Loss Speeds Up, Nearly Matches Greenland Loss

[Ted Moffett]

When skeptical arguments about climate change deny scientific fact, what can
be offered in response?  More facts?  OK, here are more facts about ice loss
in Antarctica, questioning the argument that Antarctica overall is gaining
ice:

http://www.jpl.nasa.gov/news/news.cfm?release=2008-010

January 23, 2008

PASADENA, Calif. – Ice loss in Antarctica increased by 75 percent in the
last 10 years due to a speed-up in the flow of its glaciers and is now
nearly as great as that observed in Greenland, according to a new,
comprehensive study by NASA and university scientists.

In a first-of-its-kind study, an international team led by Eric Rignot of
NASA's Jet Propulsion Laboratory, Pasadena, Calif., and the University of
California, Irvine, estimated changes in Antarctica's ice mass between 1996
and 2006 and mapped patterns of ice loss on a glacier-by-glacier basis. They
detected a sharp jump in Antarctica's ice loss, from enough ice to raise
global sea level by 0.3 millimeters (.01 inches) a year in 1996, to 0.5
millimeters (.02 inches) a year in 2006.

Rignot said the losses, which were primarily concentrated in West
Antarctica's Pine Island Bay sector and the northern tip of the Antarctic
Peninsula, are caused by ongoing and past acceleration of glaciers into the
sea. This is mostly a result of warmer ocean waters, which bathe the
buttressing floating sections of glaciers, causing them to thin or collapse.
"Changes in Antarctic glacier flow are having a significant, if not
dominant, impact on the mass balance of the Antarctic ice sheet," he said.

To infer the ice sheet's mass, the team measured ice flowing out of
Antarctica's drainage basins over 85 percent of its coastline. They used 15
years of satellite radar data from the European Earth Remote Sensing-1 and
-2, Canada's Radarsat-1 and Japan's Advanced Land Observing satellites to
reveal the pattern of ice sheet motion toward the sea. These results were
compared with estimates of snowfall accumulation in Antarctica's interior
derived from a regional atmospheric climate model spanning the past quarter
century.

The team found that the net loss of ice mass from Antarctica increased from
112 (plus or minus 91) gigatonnes a year in 1996 to 196 (plus or minus 92)
gigatonnes a year in 2006. A gigatonne is one billion metric tons, or more
than 2.2 trillion pounds. These new results are about 20 percent higher over
a comparable time frame than those of a NASA study of Antarctic mass balance
last March that used data from the NASA/German Aerospace Center Gravity
Recovery and Climate Experiment. This is within the margin of error for both
techniques, each of which has its strengths and limitations.

Rignot says the increased contribution of Antarctica to global sea level
rise indicated by the study warrants closer monitoring.

"Our new results emphasize the vital importance of continuing to monitor
Antarctica using a variety of remote sensing techniques to determine how
this trend will continue and, in particular, of conducting more frequent and
systematic surveys of changes in glacier flow using satellite radar
interferometry," Rignot said. "Large uncertainties remain in predicting
Antarctica's future contribution to sea level rise. Ice sheets are
responding faster to climate warming than anticipated."

Rignot said scientists are now observing these climate-driven changes over a
significant fraction of the West Antarctic Ice Sheet, and the extent of the
glacier ice losses is expected to keep rising in the years to come. "Even in
East Antarctica, where we find ice mass to be in near balance, ice loss is
detected in its potentially unstable marine sectors, warranting closer
study," he said.

Other organizations participating in the NASA-funded study, in addition to
the University of California, Irvine, are Centro de Estudios Cientificos,
Valdivia, Chile; University of Bristol, United Kingdom; Institute for Marine
and Atmospheric Research, Utrecht University, Utrecht, The Netherlands;
University of Missouri, Columbia, Mo.; and the Royal Netherlands
Meteorological Institute, De Bilt, The Netherlands.

Results of the study are published in February's issue of Nature Geoscience.


Additional media contact for this story: Jennifer Fitzenberger, University
of California, Irvine; 949-824-3969, jfitzen at uci.edu .

For more information, visit: http://www.nasa.gov.

JPL is managed for NASA by the California Institute of Technology in
Pasadena.

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Vision2020 Post: Ted Moffett
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