Antarctic Ice Shelf Disintegration
Underscores a Warming World
25 March 2008 Satellite imagery
from the National Snow and Ice Data Center at the University of Colorado at
Boulder reveals that a 13,680 square kilometer (5,282 square mile) ice shelf has
begun to collapse because of rapid climate change in a fast-warming region of
Antarctica.
The Wilkins Ice Shelf is a broad plate of
permanent floating ice on the southwest Antarctic Peninsula, about 1,000 miles
south of South America. In the past 50 years, the western Antarctic Peninsula
has experienced the biggest temperature increase on Earth, rising by 0.5 degree
Celsius (0.9 degree Fahrenheit) per decade. NSIDC Lead Scientist Ted Scambos,
who first spotted the disintegration in March, said, "We believe the
Wilkins has been in place for at least a few hundred years. But warm air and
exposure to ocean waves are causing a break-up."
Figure
1. This series of satellite images shows the Wilkins Ice Shelf as it began to
break up. The large image is from March 6. NSIDC processed these images from the
NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, which flies
on NASA's Earth Observing System Aqua and Terra satellites.
Satellite images indicate that the Wilkins
began its collapse on February 28; data revealed that a large iceberg, 41 by 2.5
kilometers (25.5 by 1.5 miles), fell away from the ice shelf's southwestern
front, triggering a runaway disintegration of 405 square kilometers (160 square
miles) of the shelf interior (Figure 1). The edge of the shelf crumbled into the
sky-blue pattern of exposed deep glacial ice that has become characteristic of
climate-induced ice shelf break-ups such as the Larsen B in 2002. A narrow beam
of intact ice, just 6 kilometers wide (3.7 miles) was protecting the remaining
shelf from further breakup as of March 23 (Figure
2).
Figure 2. During the break-up,
the Wilkins Ice Shelf broke into a sky-blue pattern of exposed deep glacial ice.
This true-color image of the Wilkins Ice Shelf was taken by MODIS on March 6,
2008.
Scientists track ice shelves and study
collapses carefully because some of them hold back glaciers, which if unleashed,
can accelerate and raise sea level. Scambos said, "The Wilkins
disintegration won't raise sea level because it already floats in the ocean, and
few glaciers flow into it. However, the collapse underscores that the Wilkins
region has experienced an intense melt season. Regional sea ice has all but
vanished, leaving the ice shelf exposed to the action of waves."
With Antarctica's summer melt season
drawing to a close, scientists do not expect the Wilkins to further disintegrate
in the next several months. "This unusual show is over for this
season," Scambos said. "But come January, we'll be watching to see if
the Wilkins continues to fall apart."
Real-time collaboration
Images from NASA's Moderate Resolution
Imaging Spectroradiometer (MODIS) and data from ICESat showed that the ice shelf
was in a state of collapse in March. Scambos then alerted colleagues around the
world, seeking to ensure that every means of gathering information was focused
on the break-up.
British Antarctic Survey (BAS) mounted an
overflight of the crumbling shelf, collecting video footage and other
observations. BAS glaciologist David Vaughan said of the ice shelf, which is
supported by a single strip of ice strung between two islands, "Wilkins is
the largest ice shelf on West Antarctica yet to be threatened. This shelf is
hanging by a thread."
Associate Professor Cheng-Chien Liu at
Taiwan's National Cheng-Kung University (NCKU) also responded, requesting
high-resolution color satellite images of the area from Taiwan's Formosat-2
satellite (Figure 3), operated by the National Space Organization. Cheng-Chien
Liu said, "It looks as if something is slicing the ice shelf piece by piece
on an incredible scale, kilometers long but only a few hundred meters in
width."
Figure 3. This image shows a
high-resolution, enhanced-color image of the Wilkins Ice Shelf in Antarctica on
March 8, 2008. Narrow iceberg blocks (150 meters wide, or 492 feet) crumbled
into house-sized rubble. Taiwan's Formosat-2 satellite acquired this image.
South
American scientists also got involved. Andrés Rivera and Gino Cassasa at the
Laboratorio de Glaciología y Cambio Climático at the Centro de Estudios Científicos
in Chile (CECS), acquired images of the Wilkins from the ASTER instrument,
aboard NASA's Terra satellite.
The combined efforts of these
international teams have begun to provide observational data that will improve
scientific understanding of the mechanisms behind ice shelf collapse. Scambos
said, "The Wilkins is an example of an event we don't see very often. But
it's a key process in being able to predict how sea level will change in the
future."
More information
The Wilkins is one of a string of ice
shelves that have collapsed in the West Antarctic Peninsula in the past thirty
years. The Larsen B became the most well-known of these, disappearing in just
over thirty days in 2002. The Prince Gustav Channel, Larsen Inlet, Larsen A,
Wordie, Muller, and the Jones Ice Shelf collapses also underscore the
unprecedented warming in this region of Antarctica.
This is a joint press release from the
National Snow and Ice Data Center (NSIDC), which is part of the Cooperative
Institute for Research in Environmental Sciences at the University of Colorado
at Boulder; the British Antarctic Survey (BAS), based in the United Kingdom; and
the Earth Dynamic System Research Center at National Cheng Kung University (NCKU)
inTaiwan.
Media Relations Contacts:
Stephanie Renfrow, NSIDC: srenfrow@nsidc.org
or +1 303 492-1497 (se habla Español)
Athena Dinar, BAS: amdi@bas.ac.uk or +44
(0)1223 221414
Cheng-Chien Liu, NCKU: ccliu88@mail.ncku.edu.tw
or +886-6-2757575 X65422
To view British Antarctic Survey's version of
this joint release, visit the press area of their Web site at http://www.antarctica.ac.uk/about_bas/news/press_releases.php.
For more information on the Larsen B collapse,
see http://nsidc.org/iceshelves/larsenb2002/index.html.
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