Friday, August 16, 2013

Earth orbit changes were key to Antarctic warming that ended last ice age

For more than a century scientists have known that Earth’s ice ages are caused by the wobbling of the planet’s orbit, which changes its orientation to the sun and affects the amount of sunlight reaching higher latitudes, particularly the polar regions.
he Northern Hemisphere’s last ice age ended about 20,000 years ago, and most evidence has indicated that the ice age in the Southern Hemisphere ended about 2,000 years later, suggesting that the south was responding to warming in the north.
But new research published online Aug. 14 in Nature shows that Antarctic warming began at least two, and perhaps four, millennia earlier than previously thought.
Most previous evidence for Antarctic climate change has come from ice cores drilled in East Antarctica, the highest and coldest part of the continent. However, a U.S.-led research team studying a new ice core from West Antarctica found that warming there was well under way 20,000 years ago.
“Sometimes we think of Antarctica as this passive continent waiting for other things to act on it. But here it is showing changes before it ‘knows’ what the north is doing,” said T.J. Fudge, a University of Washington doctoral student in Earth and space sciences and lead corresponding author of the Nature paper.
Co-authors are 41 other members of the West Antarctic Ice Sheet Divide project, which is primarily funded by the National Science Foundation.
The findings come from a detailed examination of an ice core taken from the West Antarctic Ice Sheet Divide, an area where there is little horizontal flow of the ice so the data are known to be from a location that remained consistent over long periods. Read More