Andrew Yee
February 24th 06, 11:15 PM
Erica Hupp/Dwayne Brown
Headquarters, Washington February 16, 2006
(202) 358-1237/1726
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-0474
RELEASE: 06-066
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
Headquarters, Washington February 16, 2006
(202) 358-1237/1726
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-0474
RELEASE: 06-066
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