PARIS, France, April 6, 2012 (ENS) – As the Envisat satellite marks 10 years in orbit, the European Space Agency says the instruments onboard continue to observe the rapid retreat of one of Antarctica’s ice shelves due to climate change.

One of the satellite’s first observations after its launch on March 1, 2002 was the break-up of a main section of the Larsen B ice shelf in Antarctica.

Envisat (Photo courtesy European Space Agency)

During that break-up, 3,200 square kilometers (1,235 square miles) of ice disintegrated within a few days “due to mechanical instabilities of the ice masses triggered by climate warming,” according to the European Space Agency.

Now, with 10 years of observations using its Advanced Synthetic Aperture Radar, ASAR, Envisat has mapped an additional loss in Larsen B’s area of 1,790 sq km (690 square miles) over the past decade.

The Larsen Ice Shelf is a series of three shelves – A (the smallest), B and C (the largest) – that extend from north to south along the eastern side of the Antarctic Peninsula.

The Larsen A ice shelf disintegrated in January 1995.

Larsen C so far has been stable, but satellite observations have shown thinning and an increasing duration of melt events in summer.

Professor Helmut Rott (Photo courtesy U. Innsbruck)

“Ice shelves are sensitive to atmospheric warming and to changes in ocean currents and temperatures,” said Professor Helmut Rott from the Institute of Meteorology and Geophysics at the University of Innsbruck in Austria.

“The northern Antarctic Peninsula has been subject to atmospheric warming of about 2.5°C over the last 50 years,” said Professor Rott, “a much stronger warming trend than on global average, causing retreat and disintegration of ice shelves.”

Professor Rott has participated in several scientific expeditions to Antarctica, Greenland and Patagonia, performing field measurements on microwave interactions with snow and ice as basis for the inversion of satellite observations.

He studied the collapse of the Larsen-A and Larsen-B ice shelves and, based on radar interferometic analysis, he provided the first evidence of the acceleration of ice streams after ice shelf disintegration.

Larsen B decreased in area from 11,512 sq km in early January 1995 to 6,664 sq km in February 2002 due to several calving events.

Break-up of the Larsen B ice shelf, 2002 (Photo by Oregon State U.)

The disintegration in March 2002 left behind only 3,463 sq km. Today, Envisat shows that only 1,670 sq km remain.

“Long-term systematic observations are of particular importance for understanding and modelling cryospheric processes in order to advance the predictive capabilities on the response of snow and ice to climate change,” said Professor Rott.

“Climate models are predicting drastic warming for high latitudes,” he said. “The Envisat observations of the Larsen Ice Shelf confirm the vulnerability of ice shelves to climatic warming and demonstrate the importance of ice shelves for the stability of glaciers upstream.”

“These observations are very relevant for estimating the future behavior of the much larger ice masses of West Antarctica if warming spreads further south,” Rott warned.

Radars on Earth observation satellites, such as Envisat’s ASAR, are particularly useful for monitoring polar regions because they can acquire images through clouds and darkness.

Envisat has already doubled its planned lifetime, but is scheduled to continue observations of Earth’s ice caps, land, oceans and atmosphere for at least another two years.

This ensures the continuity of crucial Earth observation data until the next generation of satellites, the Sentinels, begin operations in 2013.

The Sentinel missions, being developed as part of Europe’s Global Monitoring for Environment and Security program, will continue with radar observations.

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