They hope that ice cores retrieved from two tropical ice caps there, as well as ancient plants retrieved from beneath the retreating glaciers, may contain clues that could link ancient events that changed daily life in South America, Europe and Asia.

"Something happened 5,200 years ago that was abrupt and very large-scale," explained Lonnie Thompson, professor of geological sciences at Ohio State and researcher with the Byrd Polar Research Centre.

As snow falls on these ice caps and is packed tightly over time, it forms stratigraphic layers indicating annual accumulations. Researchers can estimate the age of a core by counting these layers just as biologists date forests by counting tree rings.

In September, Thompson and his team returned from drilling ice cores from glaciers atop two peaks in Peru. They drilled three cores from Nevado Coropuna, a 6,425-meter (21,074-foot) extinct volcano in the Cordillera Occidental of the Andes in Southern Peru. Two of the cores were drilled at the crater rim and measured just over 34 meters (111.5 feet).

"Based on our counting layers in the core at the drill site, we believe the shorter cores might date back at least 300 years," Thompson said.

The third core from coropuna was drilled directly over the crater at the mountains summit and measured 146.3 meters (479 feet). This core will likely provide the first annually resolved climate history for this region over at least the last 2,000 years.

There is a possibility that this core could contain glacial stage ice, he suspects, which could date it back more than 10,000 years. "These cores should provide a critical piece of the puzzle needed to understand climate variability in this region," Thompson said...