Antarctic ice shelf may be disintegrating rapidly

Washington, Apr 5 (ANI): ESA's Envisat satellite, which marks ten years in orbit, is continuing to observe the rapid retreat of one of Antarctica's ice shelves because of climate warming.

One of the satellite's first observations following its launch on 1 March 2002 was of break-up of a main section of the Larsen B ice shelf in Antarctica - when 3200 sq km of ice disintegrated within a few days due to mechanical instabilities of the ice masses triggered by climate warming.

Now, with ten years of observations using its Advanced Synthetic Aperture Radar (ASAR), Envisat has mapped an additional loss in Larsen B's area of 1790 sq km 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.

Larsen A disintegrated in January 1995. Larsen C so far has been stable in area, but satellite observations have shown thinning and an increasing duration of melt events in summer.

"Ice shelves are sensitive to atmospheric warming and to changes in ocean currents and temperatures," said Prof. Helmut Rott from the University of Innsbruck.

"The northern Antarctic Peninsula has been subject to atmospheric warming of about 2.5degreeC over the last 50 years - a much stronger warming trend than on global average, causing retreat and disintegration of ice shelves."

Larsen B decreased in area from 11512 sq km in early January 1995 to 6664 sq km in February 2002 due to several calving events. The disintegration in March 2002 left behind only 3463 sq km. Today, Envisat shows that only 1670 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 Prof. Rott.

"Climate models are predicting drastic warming for high latitudes. 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 behaviour of the much larger ice masses of West Antarctica if warming spreads further south," Prof. Rott added. (ANI)