OT : GREENLAND ICE-LOSS DOUBLES IN PAST DECADE, RAISING SEA LEVELFASTER

Feb. 16, 2006

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

Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-0474

RELEASE: 06-066 (Revised)

GREENLAND ICE-LOSS DOUBLES IN PAST DECADE, RAISING
SEA LEVEL FASTER

The loss of ice from Greenland doubled between
1996 and 2005, as its
glaciers flowed faster into the ocean in response
to a generally
warmer climate, according to a NASA/University of
Kansas study.

The study will be published tomorrow in the
journal Science. It
concludes the changes to Greenland's glaciers in
the past decade are
widespread, large and sustained over time. They
are progressively
affecting the entire ice sheet and increasing its
contribution to
global sea level rise.

Researchers Eric Rignot of NASA's Jet Propulsion
Laboratory and Pannir
Kanagaratnam of the University of Kansas Center
for Remote Sensing of
Ice Sheets, Lawrence, used data from Canadian and
European
satellites. They conducted a nearly comprehensive
survey of Greenland
glacial ice discharge rates at different times
during the past 10
years.

"The Greenland ice sheet's contribution to sea
level is an issue of
considerable societal and scientific importance,"
Rignot said. "These
findings call into question predictions of the
future of Greenland in
a warmer climate from computer models that do not
include variations
in glacier flow as a component of change. Actual
changes will likely
be much larger than predicted by these models."

The evolution of Greenland's ice sheet is being
driven by several
factors. These include accumulation of snow in its
interior, which
adds mass and lowers sea level; melting of ice
along its edges, which
decreases mass and raises sea level; and the flow
of ice into the sea
from outlet glaciers along its edges, which also
decreases mass and
raises sea level. This study focuses on the least
well known
component of change, which is glacial ice flow.
Its results are
combined with estimates of changes in snow
accumulation and ice melt
from an independent study to determine the total
change in mass of
the Greenland ice sheet.

Rignot said this study offers a comprehensive
assessment of the role
of enhanced glacier flow, whereas prior studies of
this nature had
significant coverage gaps. Estimates of mass loss
from areas without
coverage relied upon models that assumed no change
in ice flow rates
over time. The researchers theorized if glacier
acceleration is an
important factor in the evolution of the Greenland
ice sheet, its
contribution to sea level rise was being
underestimated.

To test this theory, the scientists measured ice
velocity with
interferometric synthetic-aperture radar data
collected by the
European Space Agency's Earth Remote Sensing
Satellites 1 and 2 in
1996; the Canadian Space Agency's Radarsat-1 in
2000 and 2005; and
the European Space Agency's Envisat Advanced
Synthetic Aperture Radar
in 2005. They combined the ice velocity data with
ice sheet thickness
data from airborne measurements made between 1997
and 2005, covering
almost Greenland's entire coast, to calculate the
volumes of ice
transported to the ocean by glaciers and how these
volumes changed
over time. The glaciers surveyed by those
satellite and airborne
instrument data drain a sector encompassing nearly
1.2 million square
kilometers (463,000 square miles), or 75 percent
of the Greenland ice
sheet total area.

From 1996 to 2000, widespread glacial
acceleration was found at
latitudes below 66 degrees north. This
acceleration extended to 70
degrees north by 2005. The researchers estimated
the ice mass loss
resulting from enhanced glacier flow increased
from 63 cubic
kilometers in 1996 to 162 cubic kilometers in
2005. Combined with the
increase in ice melt and in snow accumulation over
that same time
period, they determined the total ice loss from
the ice sheet
increased from 96 cubic kilometers in 1996 to 220
cubic kilometers in
2005. To put this into perspective, a cubic
kilometer is one trillion
liters (approximately 264 billion gallons of
water), about a quarter
more than Los Angeles uses in one year.

Glacier acceleration has been the dominant mode of
mass loss of the
ice sheet in the last decade. From 1996 to 2000,
the largest
acceleration and mass loss came from southeast
Greenland. From 2000
to 2005, the trend extended to include central
east and west
Greenland.

"In the future, as warming around Greenland
progresses further north,
we expect additional losses from northwest
Greenland glaciers, which
will then increase Greenland's contribution to sea
level rise,"
Rignot said.

For information about NASA and agency programs on
the Web, visit:

http://www.nasa.gov/home

For University of Kansas Center for Remote Sensing
of Ice Sheets
information, visit:

http://www.cresis.ku.edu/flashindex.htm