Antarctic's Big Thaw Began Much Earlier than Previously Believed

The Antarctic began to warm as many as 4,000 years sooner following the last ice age than previously believed, a new study suggests.

Though scientists have long known that Earth's ice ages are caused by the wobbling of the planet's orbit, most evidence has suggested that the last ice age in the Southern Hemisphere ended roughly 22,000 years ago, or 2,000 years after the Northern Hemisphere, suggesting that the south was merely responding to the warming in the north.

However, most previous evidence for climate change in the Antarctic region has come from samples taken from its eastern half, or the highest and coldest part of the continent. In an effort to get a better look of the area as a whole, a US-led team decided to take a sample from West Antarctica and, in doing so, uncovered evidence that warming was well underway in the region when North America was shedding its ice.

"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 paper published in the journal Nature.

More than two miles deep and accounting for more than 68,000 years, the ice core was analyzed by running two electrodes under the ice core in order to measure higher electrical conductivity associated with each summer season. The results pointed toward a period of greater warming between 18,000 and 22,000 years ago, or the beginning of the last deglaciation.

"This deglaciation is the last big climate change that we're able to go back and investigate," Fudge said. "It teaches us about how our climate system works."

Meanwhile, rapid warming in West Antarctica in recent decades has been documented in previous research by Eric Steig, also of the University of Washington. With this new data in hand, researchers believe say they have confirmed that West Antarctica's climate is more strongly influenced by regional conditions in the Southern Ocean than East Antarctica is.

"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.