NASA Survey Confirms Climate Warming Impact on Polar Ice Sheets(Forwarded)

Erica Hupp/Dwayne Brown
Headquarters, Washington March 8, 2006
(202) 358-1237/1726

Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
(301) 286-4044

RELEASE: 06-089

NASA SURVEY CONFIRMS CLIMATE WARMING IMPACT ON POLAR ICE SHEETS

In the most comprehensive survey ever undertaken of the massive ice
sheets covering both Greenland and Antarctica, NASA scientists
confirm climate warming is changing how much water remains locked in
Earth's largest storehouses of ice and snow.

"If the trends we're seeing continue and climate warming continues as
predicted, the polar ice sheets could change dramatically," said
survey lead author Jay Zwally of NASA's Goddard Space Flight Center,
Greenbelt, Md. "The Greenland ice sheet could be facing an
irreversible decline by the end of the century."

Other recent studies have shown increasing losses of ice in parts of
these sheets. This new survey is the first to inventory the losses of
ice and the addition of new snow on both continents in a consistent
and comprehensive way throughout an entire decade.

The survey shows there was a net loss of ice from the combined polar
ice sheets between 1992 and 2002 and a corresponding rise in sea
level. The survey documented for the first time extensive thinning of
the West Antarctic ice shelves, an increase in snowfall in the
interior of Greenland and thinning at the edges. All are signs of a
warming climate predicted by computer models.

The survey combines new satellite mapping of the height of the ice
sheets from two European Space Agency satellites. It also used
previous NASA airborne mapping of the edges of the Greenland ice
sheets to determine how fast the thickness is changing. Researchers
used nine years of elevation mapping over much of Antarctica and 10.5
years of data over Greenland from the European Remote-sensing
Satellites 1 and 2. The survey pinpointed where the ice sheets were
thinning and where they were growing.

In Greenland, the survey saw large ice losses along the southeastern
coast and a large increase in ice thickness at higher elevations in
the interior due to relatively high rates of snowfall. This study
suggests there was a slight gain in the total mass of frozen water in
the ice sheet over the decade studied, contrary to previous
assessments.

According to Zwally, this situation may have changed in just the past
few years. Last month NASA scientists at the Jet Propulsion
Laboratory, Pasadena, Calif., reported a speed up of ice flow into
the sea from several Greenland glaciers. That study included
observations through 2005; Zwally's survey concluded with 2002 data.

"The melting of ice at the edges of the ice sheet is also increasing,
which causes the ice to flow faster," Zwally said. "A race is going
on in Greenland between these competing forces of snow build-up in
the interior and ice loss on the edges. But we don't know how long
they will be approximately in balance with each other or if that
balance has already tipped in favor of the recently accelerating
outflow from glaciers."

The situation was very different in Antarctica. The ice sheets had a
major net loss of ice due to outflow from West Antarctica. These
loses, which may have been going on for decades, outweighed the gains
in snow and ice seen in the East Antarctic ice sheet and parts of
West Antarctica. Also thinning were the ice shelves around West
Antarctica, where temperatures have been increasing. The floating ice
shelves are vulnerable to climate change. Some ice shelves in the
Antarctic Peninsula have totally disintegrated in recent years,
allowing the ice from the land to move into the ocean faster.

When the scientists added up the gains and loses of ice from the
Greenland and Antarctic sheets, there was a net loss of ice to the
sea. The Greenland ice sheet annually gained approximately 11 billion
tons of water, while Antarctica lost about 31 billion tons per year.
The 20 billion net tons added to the oceans is equivalent to the
amount of fresh water annually used in homes, businesses and farming
in New York, New Jersey and Virginia.

"The study indicates that the contribution of the ice sheets to
sea-level rise during the decade studied was much smaller than
expected, just two percent of the recent increase of nearly three
millimeters (0.12 inches) a year," Zwally said. "Current estimates of
the other major sources of sea-level rise -- expansion of the ocean by
warming temperatures and runoff from low-latitude glaciers -- do not
make up the difference, so we have a mystery on our hands as to where
the water is coming from. Continuing research using NASA satellites
and other data will narrow the uncertainties in this important issue
and help solve the mystery."

The survey was published this week in the Journal of Glaciology
(www.igsoc.org). For more information about the research and images
on the Web, visit:
http://www.nasa.gov/vision/earth/env...ce_sheets.html