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February 16, 2006
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, Pasadena, Calif., 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 University of Kansas Center for Remote Sensing of Ice Sheets information on the Web, visit:
http://www.cresis.ku.edu/flashindex.htm
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Contact:
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
Erica Hupp/Dwayne Brown
NASA Headquarters, Washington
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Break-off Point of Helheim Glacier
This image shows the calving front, or break-off point into the ocean, of Helheim Glacier, located in southeast Greenland. The image, taken in May
2005, shows high calving activity associated with faster glacial flow. This glacier is now one of the fastest moving glaciers in the world. Image
credit: NASA/Wallops
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