Antarctic Ice Loss Speeds Up, Nearly Matches Greenland Loss
Pastor Dale Morgan
Antarctic Ice Loss Speeds Up, Nearly Matches Greenland Loss*
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.
by Staff Writers
Pasadena CA (SPX) Jan 24, 2008
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.