David E. Steitz

Headquarters, Washington, DC

(Phone: 202/358-1730)

Lynn Chandler

Goddard Space Flight Center, Greenbelt, MD

(Phone: 301/614-5562)

RELEASE: 00-112

Scientists who want to monitor the state of our global
climate may have to look no farther than the coastal ice that
surrounds the Earth’s largest island.

A NASA study of Greenland’s ice sheet reveals that it is
rapidly thinning. In an article published in the July 21 issue of
Science, Bill Krabill, project scientist at the NASA Goddard Space
Flight Center’s Wallops Flight Facility, Wallops Island, VA,
reports that the frozen area around Greenland is thinning, in some
places, at a rate of more than three feet per year. Any change is
important since a smaller ice sheet could result in higher sea

“A conservative estimate, based on our data, indicates a net
loss of approximately 51 cubic kilometers of ice per year from the
entire ice sheet, sufficient to raise global sea level by 0.005
inches per year, or approximately seven percent of the observed
rise,” Krabill said.

“This amount of sea level rise does not threaten coastal
regions, but these results provide evidence that the margins of
the ice sheet are in a process of change,” Krabill said. “The
thinning cannot be accounted for by increased melting alone. It
appears that ice must be flowing more quickly into the sea through

Greenland covers 840,000 square miles and 85 percent of the
island is covered by ice, some of which is up to two miles thick.
With its southern tip protruding into temperate latitudes,
monitoring this portion of the ice sheet may be one of the best
ways to measure changes in our climate, at least in the Northern

The ice mapping was completed by NASA, which has been
surveying the Greenland ice sheet for nearly seven years. In 1993
and 1994, NASA researchers surveyed the ice sheet using an
airborne laser altimeter and precision global positioning
satellite receivers. Those same areas were surveyed again in 1998
and 1999.

Now, for the first time, portions of the entire ice sheet
covering Greenland have been mapped with sufficient accuracy to
detect significant changes in elevation.

Krabill noted that while some internal areas of Greenland
show slight ice thickening, most areas along the coast show
significant thinning. “Why the ice margins are thinning so rapidly
warrants additional study,” according to Krabill. “It may
indicate that the coastal margins of ice sheets are capable of
responding more rapidly than we thought to external changes, such
as a warming climate.”

“For the first time, we are seeing evidence that one of the
two great ice bodies on the Earth (the other is the Antarctic ice
sheet) is contributing, in a modest fashion, to observed sea level
rise,” said Dr. Ghassem Asrar, Associate Administrator for NASA’s
Office of Earth Science. “NASA’s ICESat spacecraft, which is
scheduled for launch in 2001, will allow us to make similar
measurements routinely and keep an eye on both Antarctica and

The Office of Earth Science, NASA Headquarters, Washington,
DC sponsors the Greenland ice mapping project. NASA’s Office of
Earth Sciences studies long-term climate trends to learn how
human-induced and natural changes affect our global environment.

Further information on the Greenland mapping project,
including the technology behind the science, is available at:


Imagery supporting this story is available at:


More information about the Office of Earth Sciences can be
found at: