Using radiocarbon analyses of abandoned colonies on the Victoria Land coast of the Ross Sea, scientists believe that modern, ice-free conditions developed in the region only within roughly the past 1,000 years and that the present Adelie colonies on Ross Island, which are among the most numerous in the world, are likely no more than 500 years old.
Those techniques, they say, can also help to refine our understanding of climatic change on the southernmost continent
"We think the birds left the colonies when the southern Ross Sea was completely iced over in a cooling trend that very likely covered that region for probably a thousand years," said Steven D. Emslie, of the University of North Carolina at Wilmington. "That's never been known before from other climate records."
Scientists typically use chemical signatures in marine sediments, ice cores and other natural records to piece together a picture of what the Antarctic climate looked like thousands and even millions of years ago. But those records do not provide a highly defined or detailed picture of climate over shorter geological time scales.
"The evidence from these colonies can help refine those other records," said Emslie. "They are adding a higher resolution to the climatic record in Antarctica."
The National Science Foundation (NSF) funded Emslie's work, which was published recently in the journal Marine Ecology Progress Series. NSF is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of nearly $5 billion.