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Satellite Images Show Antarctic Ice Sheet Losing Mass
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http://enews.voanews.com/t?ctl=113352D:3919ACA Data from pair of
satellites orbiting  globe marks first time scientists have been able
to survey entire ice blanket  The Antarctic ice sheet is losing mass,
according to scientists using data from a pair of satellites orbiting
the globe. This is the first time scientists have been able to survey
the entire ice blanket. The study confirms prior studies that the
sheet is melting.

The Antarctic ice sheet is responsible for 90 percent of the world's
ice. Studies over the past several years have showed that the sheet is
losing mass, causing a rise in global sea surface levels.

But the conclusions have been reached based on snapshots of parts of
the ice blanket, such as its thinning edges.







Gravity Recovery and Climate Experiment satellite (GRACE)"But you know
now what's going on which I think is pretty good," said Isabella
Velicogna, who is with the University of Colorado's Cooperative
Institute for Research and Environmental Sciences and lead scientist
on the GRACE project, which stands for Gravity Recovery and Climate
Experiment.

Launched by the U.S. space agency NASA and Germany in 2002, GRACE
employs two satellites that circle the globe 16 times a day, sensing
subtle changes in earth's mass and gravitational field.

The satellites orbit 220 kilometers apart. As one satellite passes
over an irregular mass on the ice sheet, it emits a slightly increased
gravitational pull that slows it down slightly, and the deceleration
is recorded by the other satellite.

After many passes back and forth, a picture begins to emerge,
according to Velicogna.



"As it turns out if you can measure changes in distance between the
two satellites, you can get information about what's underneath and
what's causing those changes," she said. "And you can get information
when you fly over the ice sheet about the mass change of the ice
sheet."

In a paper published in the current issue of Science, Veliconga and
co-author John Wahr, also of the University of Colorado, report the
ice blanket appears to be losing mass at an annual rate of 152 cubic
kilometers.

That confirms estimates from earlier studies. At that rate, Veliconga
says, global sea surface levels will rise an average of 0.4
millimeters per year.

The University of Colorado's Isabella Veliconga says no one knows for
certain whether the ice sheet will continue to shrink and contribute
to a rise in ocean levels.

But she says that scientists now have a more comprehensive way to
monitor it.

"If we will be able to have projections for sea level change that will
help from a sociological point of view, and it would help our everyday
life, maybe not our immediate life but our kids, and the kids of our
kids," she said. "So, it's very exciting to be part of this."