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Rugged mountains topped by ice.
Photo Credit: Janice O'Reilly
The Antarctic Peninsula where new research suggests that tropical influences are causing widespread warming during the autumn months of March, April and May in the Southern Hemisphere.

Temperatures rise in the fall

Study suggests tropics to blame for warming during autumn months 

A new study in the Journal of Climate suggests widespread warming across the Antarctic Peninsula during the fall is being influenced by atmospheric circulation patterns originating in the tropics.

Previously, researchers have documented that temperatures have been rising about half a degree Celsius per decade for the last 50 years across parts of the peninsula. In addition, sea ice duration during the winter months has decreased dramatically. Scientists have attributed these phenomena to human-induced climate change and ozone depletion. [State of the Antarctic — State of the Antarctic: New SCAR report shows continent undergoing major changes.]

The new research from scientists at the University of Washington External Non-U.S. government site provides evidence that warming during March, April and May is being driven by large-scale atmospheric circulation originating in the equatorial Pacific Ocean that affects the entire peninsula region.

The warm sea surface generates an atmospheric phenomenon called a Rossby wave train, which reaches the Antarctic Peninsula and alters the local circulation to warm the region. [See previous article — Heat wave: UW scientists suggest Pacific Ocean contributes to West Antarctic warming.]

The sea-surface temperature trend in the tropical Pacific is related to natural phenomena such as the El Niño Southern Oscillation External U.S. government site (El Niño and La Niña) and cycles that occur on longer timescales, sometimes decades. But it is not clear whether human causes play a role in that trend, according to the researchers.

"We still lack a very clear understanding of the tropical natural variability, of what that dynamic is," said Qinghua Ding External Non-U.S. government site, a University of Washington research associate in Earth and space sciences and lead author on the paper. 

For further information, see the University of Washington press release External Non-U.S. government site