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| Radar images from the Envisat satellite from 2002 to 2012 of the Larsen B ice shelf in Antarctica. Over the last decade, the ice shelf has disintegrated by 1790 sq km. (Credit: ESA) |
ScienceDaily, April 5, 2012
As ESA's Envisat
satellite marks ten years in orbit, it continues to observe the rapid retreat
of one of Antarctica's ice shelves due to 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 2.5°C 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.
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) programme -- will continue the legacy of radar
observations.
Story Source:
The above story is reprinted from materials provided by European Space Agency (ESA), via AlphaGalileo.
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