New research suggests West Antarctica's warming began more than 20,000 years ago, much earlier than previously believed, according to a University of Washington news release.
"The 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," the University said. "Suggesting that the south was responding to warming in the north."
However, the past research is contradicted as new findings from West Antarctica's core ice shows warming began at least 2,000 to 4,000 years earlier.
The study was published online in Nature.
Previous evidence used to indicate Antarctica's climate change has come from ice core drilled in East Antarctica, the highest and coldest part of the continent, according to the news release.
"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.
Researchers provided the following explanation of their findings:
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.
The ice core is more than 2 miles deep and covers 68,000 years, though so far data have been analyzed only from layers going back 30,000 years. Near the surface, 1 meter of ice covers one year, but at greater depths the annual layers are compressed to centimeters.
Fudge identified the annual layers by running two electrodes along the ice core to measure higher electrical conductivity associated with each summer season. Evidence of greater warming turned up in layers associated with 18,000 to 22,000 years ago, the beginning of the last deglaciation.
"This deglaciation is the last big climate change that that we're able to go back and investigate," Fudge said. "It teaches us about how our climate system works."
West Antarctica is separated from East Antarctica by a major mountain range. East Antarctica has higher elevations, which makes it colder than the west, but there is also recent evidence that it is also warming.
"It's not surprising that West Antarctica is showing something different from East Antarctica on long time scales, but we didn't have evidence for that before," Fudge said.
Researchers noted Earth's orbit is not an important factor in the rapid warming.
"Earth's orbit changes on the scale of thousands of years, but carbon dioxide today is changing on the scale of decades so climate change is happening much faster today," Fudge said.
