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Satellites show rapid disintegration of Larsen ice shelves

The Larsen B ice shelf is about 90 percent smaller than it was in 1995.

Part of the Larsen ice shelf has declined by 90 percent, according to measurements by an Envisat satellite

By Summit Voice

SUMMIT COUNTY — A European satellite that’s been monitoring Antarctic sea ice for the past 10 years has documented additional disintegration of the Larsen ice shelf area, along the east side of the Antarctic peninsula.

The Larsen B ice shelf has shown the most significant decline since 1995, shrinking by about 90 percent, from 11,512 square kilometers to just 1,67o square kilometers this year.

The European Space Agency’s Envisat satellite first documented the wasting in 2002, shortly after its launch, when when 3200 sq km of ice disintegrated within a few days due to mechanical instabilities of the ice masses triggered by warming climate temperatures in the region.

Air temperatures around the Antarctic Peninsula are increasing at a greater rate than many other areas —   by about 2.5 degrees Celsius in the past 50 years, confirmed by data from NASA satellites.

“Ice shelves are sensitive to atmospheric warming and to changes in ocean currents and temperatures,” said Prof. Helmut Rott from the University of Innsbruck, one of the scientists evaluating the Envisat data.

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

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.

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.

“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.”

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.

The Sentinel missions – being developed as part of Europe’s Global Monitoring for Environment and Security (GMES) program — will continue the legacy of radar observations.

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