Ice sheets can retreat in a "geologic instant".

• Position: Paleoclimatology

Modern glaciers, such as those making up the ice sheets in Greenland and Antarctica, are capable of undergoing periods of rapid shrinkage or retreat, according to findings by paleoclimatologists at the University at Buffalo (N.Y), whose fieldwork demonstrates that a prehistoric glacier in the Canadian Arctic rapidly retreated in just a few hundred years. The proof of such rapid retreat of ice sheets provides one of the few explicit confirmations that this phenomenon occurs. Should the same conditions recur today, which some scientists say is very possible, they would result in sharply rising global sea levels, which would threaten coastal populations.

"A lot of glaciers in Antarctica and Greenland are characteristic of the one we studied in the Canadian Arctic," declares Jason Briner, assistant professor of geology. "Based on our findings, they, too, could retreat in a geologic instant."

These findings will allow scientists to predict more accurately how global warming will affect ice sheets and the potential for rising sea levels in the future by developing more robust climate and ice sheet models. Briner emphasizes the findings especially are relevant to the Jakobshavn Isbrae, Greenland's largest and fastest moving tidewater glacier, which is retreating under conditions similar to those he studied in the Canadian Arctic.

Acting like glacial conveyor belts, tidewater glaciers are the primary mechanism for draining ice sheet...