Apr 04, 2008

Satellite images reveal collapsing ice shelf

Taiwan’s FORMOSAT-2 satellite is playing an integral role in assisting the international scientific community monitor the breakup of an ice shelf in Antarctica by providing detailed real-time images of the phenomenon, which began Feb. 28.

Estimated Article Reading Time: 3 min.

According to Liu Cheng-chien, an associate professor at the National Cheng Kung University’s Department of Earth Sciences in Tainan, the satellite started taking photographs on a day-to-day basis of the 14,500-square-kilometer Wilkins Ice Shelf in Antarctica March 7 after a request from National Snow and Ice Data Center at the University of Colorado in the United States.

“Ted Scambos, chief scientist at the NSIDC, noticed the ice shelf had begun collapsing after reviewing U.S. satellite data,” Liu said. “He contacted us as a way of ensuring that every means at the international scientific community’s disposal of gathering information was focused on the break-up.”

The Wilkins Ice Shelf is a broad plate of permanent floating ice on the southwestern Antarctic Peninsula, about 1,600 kilometers 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 per decade.

Information made available to Scambos by the U.S. National Aeronautics and Space Administration’s Terra and Aqua satellites, and the center’s Ice, Cloud, and Land Elevation Satellite, first alerted him that Wilkins had begun its collapse. Images revealed that a massive iceberg fell away from the ice shelf’s southwestern front, triggering a 570-square-kilometer disintegration of the shelf interior.

The melted area is twice the size of Taipei City, or nine times that of Manhattan Island’s land mass. A narrow beam of intact ice just kilometers wide was all that remained from halting the shelf from further breakup as of March 23.

Liu immediately responded to his stateside colleague’s call for assistance by requesting imagery from FORMOSAT-2, the first and only very-high resolution satellite with a daily revisit capability. “We were excited to be able to assist by utilizing our nation’s satellite that possesses such high imagery resolution,” the Taiwanese scientist added.

Launched into space May 2004 from the Vandenberg Air Force Base located on California’s central coast in the United States, FORMOSAT-2 is the first remote sensing satellite developed and operated by the Hsinchu-based National Space Organization under the Cabinet-level National Science Council. Formerly known as ROCSAT-2, the satellite—designed in Europe and built by EADS Astrium—completes exactly 14 orbital revolutions every day and is an integral part of disaster management processes, such as those used to evaluate 2004 South Asia Tsunami and last year’s wildfires in California.

Capturing very-high resolution images of the disintegrating ice shelf using its panchromatic and multi-spectral image-capture systems, the aftermath of the collapse was documented in remarkable detail. “It looked as if something was slicing the ice shelf piece by piece on an incredible scale,” Liu said. “The ice sheets are kilometers long but only a few hundred meters in width.”

In comparison to other images captured using the Moderate Resolution Imaging Spectroradiometer sensors on NASA’s satellites, and from a surveillance aircraft, the FORMOSAT-2 photographs are superior because they provided more spatial details. According to Liu, who developed the automatic image-processing system for the US$137.8 million satellite, most of its commercial competitors equipped with high image resolution capability are restricted in high-latitude areas of Antarctic observation.

With scientists tracking ice shelves and studying collapses carefully because some of them hold back glaciers—which if unleashed can increase sea levels—the importance of FORMOSAT-2 to this process was underlined when David Vaughan and Andrew Fleming of the British Antarctic Survey ordered an aerial surveillance of Wilkins after studying images provided by the satellite.

Vaughan, who in 1993 predicted that the northern part of Wilkins was likely to be lost within 30 years if climate changes on the Peninsula were to continue at the same rate, said: “Wilkins is the largest ice shelf on the Antarctic Peninsula yet to be threatened. This ice shelf is hanging by a thread and we will know in the next few weeks what its fate will be.”

Scambos agreed that Wilkins is under threat but explained that with Antarctica’s summer melt season drawing to a close, scientists do not expect to see any further disintegration over the next several months. “The ice shelf’s collapse underscores that the region has experienced an intense melt season,” he said. “This unusual show is over for this season, but come January, we’ll be watching to see if the Wilkins continues to fall apart.”

The Wilkins Ice Shelf is one of string of ice masses to have collapsed in the West Antarctic Peninsula over the past 30 years. In 2002, the Larsen B became the most well known of these, disappearing in just over 30 days. Six other shelves have also been lost entirely—the Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller and Jones—underscoring the unprecedented warming in this region of Antarctica.

Write to Edwin Hsiao at edwinhsiao@mail.gio.gov.tw