The West Antarctic Ice Sheet is still dropping huge chunks of iceberg that drift hundreds of miles while they slowly melt, but it may have stopped melting, meaning that there will not be a rise in ocean levels in the immediate future. NASA?s Jet Propulsion Laboratory and the California Institute of Technology say their measurements show the ice sheet is getting thicker. ?We find strong evidence for ice-sheet growth,? say Ian Joughlin and Slawek Tulaczyk. Other scientists have been taking measurements showing the ice sheet, known to scientists as the WAIS, has been steadily melting since the end of the last Ice Age about 11,000 years ago.
It currently covers about 360,000 square miles has enough ice to raise global sea levels by five to 18 feet if it melts. Earlier predictions said that it could melt in 4,000 years.
The United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC) predicts the average global temperature could be as much as 11 degrees higher at the end of the century than it was in 1990. If this affected the Antarctic, it could melt enough ice to raise sea levels enough to swamp coastal areas and drown island nations. It would also greatly alter the Earth?s climate by changing ocean currents and temperatures.
But experts say there is little evidence that global warming is responsible for melting the ice sheet. Currents and the way water washes underneath the floating portions seems to have more of an effect.
Joughlin and Tulaczyk used satellite radar to measure the thickness of the ice. They specifically looked at ice streams, which are similar to large, flowing rivers of ice.While previous measurements had suggested ice was being steadily lost, they found that there was slightly more ice in the areas feeding the streams than before. Overall, there were 26 billion tons more ice each year, not the loss of nearly 21 billion tons a year that other studies showed.
They say the West Antarctic ice streams may be undergoing the same transition from shrinking to growing that appears to have occurred on a neighboring stream 150 years ago. This means there?s less possibility of the feared massive collapse of the ice field.
Richard Allen of Pennsylvania State University says, ?Perhaps after 10,000 years of retreat from the ice-age maximum, researchers turned on their instruments just in time to catch the stabilization or re-advance of the ice sheet.?
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