N° 36–1998: Antarctica is not shrinking

The team of British, Dutch and American scientists, led by Professor Duncan Wingham at University College London, based their findings on ERS data collected over five years.

The data reveal that most of the ice stored in Antarctica is very stable. The icy continent now looks an unlikely source of rising global sea level this century, making thermal expansion of the ocean due to global warming, and the shrinking of mountain glaciers, more likely causes.

Prof. Wingham's team used ERS's radar altimeter instruments to determine if the thickness of the Antarctic Ice Sheet changed over the five-year period from 1992 to 1996. Transmitting over 4,000,000 radar pulses to the surface of the ice, and measuring the time taken for the echoes to return to the satellite, the average change of the height of 63 of the Ice Sheet was measured with an accuracy of 0.5 cm per year. The ice sheet has changed on average by less than 1 cm per year. Using previous measurements of changes in snowfall over the ice sheet, the team concluded that the interior of the Antarctic Ice Sheet had contributed only 1.7 cm to sea level rise this century.

Sea level has risen 18 cm over the past 100 years. Previously the accuracy of data could have meant that Antarctica were responsible for a raise or lowering of global sea level by 14 cm in either direction. Speaking today on the importance of the research Professor Duncan Wingham said: "Scientists have never really understood the role that Antarctica has played in this century's rising sea level. Our research makes it likely that the answer is very little."

The result supports the view that global warming, leading to a thermal expansion of the ocean and the melting of mountain glaciers, is responsible for rising sea level. Professor Wingham continued, "As a consequence of our research we should be able to produce more accurate predictions of future sea level rises. Indeed it is possible that the consequences of global warming on sea level rise has been underestimated." Professor Wingham and his team also discovered a rapid reduction in thickness in one of West Antarctica's least known drainage basins. The Thwaites Glacier basin was shrinking rapidly at 12 cm per year. The result provides evidence that one of the most hostile regions of Antarctica may be undergoing rapid change.

Commenting on the wider importance of the research, ESA's Earth Observation Mission Manager Guy Duchossois said: "Knowledge about sea level rise matters for many million people in coastal areas whose lives depend on dykes that can withstand the forces of nature. ESA will continue to fly satellites that provide the data for a better understanding of our environment. Global warming may have daunting consequences that satellites in space can help to manage."

Further information: Franco Bonacina, Media Relations, European Space Agency, 00 33 1 5369 7713 Patrick Edwards, Head of Media Relations, 0171 391 1621 Linda Capper, British Antarctic Survey, 01223 221 448

NOTES TO EDITORS.
(i) Antarctic Elevation Change 1992 - 1996, D.J.Wingham et al. Appears in the 16 October 1998 edition of SCIENCE