Ice Sheet Seen Melting From Space
W A S H I N G T O N, Feb. 2, 2001 -- Scientists have worried for decades that theAntarctic ice sheet was shrinking, threatening a global rise in sealevel. Now, satellite studies show that about 7.5 cubic miles ofice have eroded from a key area in just eight years.
Melting of that much ice doesn't mean that it is time to getinto boats, said one researcher, but the finding may be a "yellowwarning flag" that confirms long-term changes are under way in theice fields covering the South Polar region.
The study, which appears today in the journal Science, involvedaltitude measurements of the West Antarctica Ice Sheet, the smallerof two major ice sheets. It covers 740,000 square miles of thefrozen continent.
‘Weak Underbelly’
Based on satellite measurements, said Andrew Shepherd, aUniversity College London geologist and first author of the study,it appears that since 1992 the ice sheet has lost ice principallythrough the speeded-up movement of the Pine Island Glacier, an icestream that drains about a third of the ice sheet.
"The Pine Island Glacier is key," said Shepherd. "It istotally exposed to the sea, and people have identified it as theweak underbelly of the West Antarctica Ice Sheet."
Melting of the entire sheet theoretically could cause a globalsea level rise of 25 to 45 feet, but Shepherd said that at thepresent rate of change it would take centuries for the Pine IslandGlacier, which is only about 10 percent of the ice sheet, to affectsea level seriously.
Jane Ferrigno, a U.S. Geologic Survey geologist and polar iceexpert, said a speedup of the Pine Island Glacier, as reported byShepherd and his co-authors, could foreshadow continuing changes ofthe West Antarctica Ice Sheet's ice levels.
The glacier "is moving faster than we thought," Ferrigno said."This doesn't mean it could have an effect on coastal areas aroundthe world within the next few decades, but this is a yellow warningflag. This is an area that should be watched carefully."
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