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SCIENCE: A Satellite for Solving the Polar Ice Mysteries

Julio Godoy* - Tierramérica

PARIS, Apr 8 2006 (IPS) - The European satellite Cryosat 2, slated for launch in March 2009, will determine for the first time the rate of polar ice melt, which is a vital piece for understanding the changes the planet’s climate is undergoing, mission director Volker Liebig told Tierramérica.

The failed launch of the first Cryosat, in October 2005, proved a considerable setback for the world scientific community specialised in studying the impact of the greenhouse effect on the volume of ice at the poles.

But the European Space Agency (ESA), which as part of its Earth Observation programme had worked toward its launch, did not give up on the mission, and will relaunch with new technology for putting the satellite into orbit – and ensuring its success.

“The Cryosat mission for measuring the rates of change in the ice mass at the poles over three years is crucial for understanding the consequences of atmospheric warming,” said Liebig, director of ESA’s Earth Observation programme.

So far, the estimates about ice volume at the poles are based on isolated measurements and offer contradictory results. For example, some figures indicate that while the ice surface in the Arctic diminished nine percent in 30 years, it increased by about the same amount in that period in the Antarctic.

The Cryosat 2 mission, which was given the green light in February, should provide definitive information in this regard.

“Cryosat 2 will measure the density of the ice, both in the ice mass at the poles and in the seas, to analyse the link between the melting of those masses and the rise in sea level, and what role climate change plays,” said Liebig.

The scientist indicated that for ESA it is important to study how these phenomena alter the Gulf Stream of the northern Atlantic Ocean, and its effects on the climate of Northern Europe.

“The climate in European regions like the British Isles and the Scandinavian countries is determined by the Gulf Stream, which makes it very different from zones located at the same distance from the equator in North America, like Canada and Alaska,” Liebig explained. “The melting at the poles will surely change the nature of the Gulf Stream, affecting the climate of Northern Europe.”

Several scientific bodies have established that polar melt has been constant for years.

In September, the U.S. National Snow and Ice Data Centre (NSIDC) estimated that the ice at the North Pole is melting at a rate of eight percent every 10 years, and if the trend continues, by the end of the 21st century the ice could disappear from the Arctic during the boreal summer.

According to NSIDC measurements, the ice surface in the Arctic covered 5.32 million square kilometres, the lowest reading since satellites began taking these measurements in 1978.

To confirm and clarify these measurements, beginning in March 2009 and over the next three years, Cryosat 2 will orbit the Earth at an unusually sharp angle for meteorological satellites, in order to reach 88 degrees latitude north and south.

“For normal meteorological satellites there is a blind angle that prevents them from observing certain points on the Earth. For the Cryosat 2, the blind angle doesn’t exist,” said Liebig.

Furthermore, a special radar system known as SIRAL – the main instrument of the satellite and operable under all climate conditions – will have the most advanced technology for obtaining exact measurements of the thickness of polar ice.

The SIRAL has two antennae that emit radar signals and receive their echoes reflected by the ice surface at the poles. The two antennae function like two human eyes, allowing a three-dimensional view of the polar mass.

The radar operates in coordination with the Cryosat programme for measuring orbits and high-precision radio positioning system, DORIS, complemented by a system fed by retroreflection laser rays.

This complex measurement system will allow the Cryosat 2 to obtain millimetre-accurate images of the irregular and inclined surfaces of polar ice, as well as the ice masses floating in the oceans. It will also be possible to measure the exact velocity of glacial flows, paving the way for conclusions about the degree of global climate change occurring.

Liebig explained that the measurement-taking technology of the meteorological satellite was not to blame for the failure of the first attempted Cryosat mission.

“The fall of the Cryosat was due to an error in the launch rocket. But its observation technology functions perfectly and is the most advanced available,” he assured.

(*Julio Godoy is an IPS correspondent. Originally published Apr. 1 by Latin American newspapers that are part of the Tierramérica network. Tierramérica is a specialised news service produced by IPS with the backing of the United Nations Development Programme and the United Nations Environment Programme.)