[asa] ESA: Wilkins Ice Shelf under threat

http://www.esa.int/esaEO/SEMXK5AWYNF_planet_0.html

28 November 2008
New rifts have developed on the Wilkins Ice Shelf that could lead to
the opening of the ice bridge that has been preventing the ice shelf
from disintegrating and breaking away from the Antarctic Peninsula.

The ice bridge connects the Wilkins Ice Shelf to two islands, Charcot
and Latady. As seen in the Envisat image above acquired on 26 November
2008, new rifts (denoted by colourful lines and dates of the events)
have formed to the east of Latady Island and appear to be moving in a
northerly direction.
Dr Angelika Humbert from the Institute of Geophysics, Münster
University, and Dr Matthias Braun from the Center for Remote Sensing,
University of Bonn, spotted the newly formed rifts during their daily
monitoring activities of the ice sheet via Envisat Advanced Synthetic
Aperture Radar (ASAR) acquisitions.

"These new rifts, which have joined previously existing rifts on the
ice shelf (blue dotted line), threaten to break up the chunk of ice
located beneath the 21 July date, which would cause the bridge to lose
its stabilisation and collapse," Humbert explained. "These recent
changes are happening slower and more continuously than the events we
saw earlier this year."

In February 2008 an area of about 400 km² broke off from the ice
shelf, narrowing the ice bridge down to a 6 km strip. At the end of
May 2008 an area of about 160 km² broke off, reducing the ice bridge
to just 2.7 km. Between 30 May and 9 July 2008, the ice shelf
experienced further disintegration and lost about 1 350 km².

The Wilkins Ice Shelf, a broad plate of floating ice south of South
America on the Antarctic Peninsula, had been stable for most of the
last century before it began retreating in the 1990s. The peninsula
has been experiencing extraordinary warming in the past 50 years of
2.5°C.

If the ice shelf breaks away from the peninsula, it will not cause a
rise in sea level since it is already floating. However, ice shelves
on the Antarctic Peninsula are sandwiched by extraordinarily raising
surface air temperatures and a warming ocean, making them important
indicators for on-going climate change.

Long-term satellite monitoring over Antarctica is important because it
provides authoritative evidence of trends and allows scientists to
make predictions. Over the last 17 years, ESA’s ERS and Envisat
satellite missions have been the main vehicles for testing and
demonstrating the use of Earth Observation data in Polar Regions.

In the past 20 years, seven ice shelves along the Antarctic Peninsula
have retreated or disintegrated, including the most spectacular break-
up of the Larsen B Ice Shelf in 2002, which Envisat captured within
days of its launch.

Envisat’s ASAR instrument is particularly suited to acquire images
over Antarctica during the local winter period because it is able to
produce high-quality images through bad weather and darkness,
conditions often found in the area.

Daily ASAR images of Antarctica are easily accessible to scientists.
ESA will publish an update about the status of the Wilkins Ice Shelf
in the event of a break-up.
  

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Received on Sat Nov 29 14:36:12 2008