People living in low-lying coastal regions should brace for major floods as an immense expanse of Antarctic ice disintegrates. No need to pack just yet, though. Researchers expect the floods sometime in the next 7,000 years.
The potential culprit is the West Antarctic Ice Sheet, which rests on the Antarctic land mass below sea level. The ice sheet, which covers about 360,000 square miles, has been receding steadily for 10,000 years. It poses the most immediate threat of a large sea level rise because of its potential instability, according to a new study by led by Howard Conway, UW research associate professor of geophysics.
While human-caused climate change could hasten the ice sheet’s demise, it might be that there is nothing humans can do to slow or reverse the trend, says Conway.
“Collapse appears to be part of an ongoing natural cycle, probably caused by rising sea level initiated by the melting of the Northern Hemisphere ice sheets at the end of the last ice age,” explains Conway. “But the process could easily speed up if we continue to contribute to warming the atmosphere and oceans.”
| "Collapse appears to be part of an ongoing natural cycle . . . but the process could easily speed up if we continue to contribute to warming the atmosphere and oceans." |
Using evidence gathered from raised beaches and radar imaging of subsurface ice structures to reconstruct historic changes, the scientists found the ice sheet has both thinned and decreased in area since the last glacial maximum 20,000 years ago.
Ice covering the region once was as much as a half-mile thick in places. Land previously weighed down by the dense ice has elevated since being freed from its burden. The timing of deglaciation was determined by carbon-14 dating of samples found on raised beaches that are now up to 90 feet above present sea level.
Other evidence comes from Roosevelt Island, an ice island in the Ross Sea. Floating ice now surrounds it, but reconstructions suggest that ice in the area of Roosevelt Island was about 1,600 feet thicker and was grounded during the last ice age.
Researchers working with Conway on this study included Professor Edwin Waddington and Research Associate Anthony Gades of the UW Department of Geophysics, and Professor George Denton and post-doctoral researcher Brenda Hall of the University of Maine.
[Winter 2000 - Table of Contents]