New glacier history sheds light on climate change

New glacier history sheds light on climate change

By Phoebe Dey, ExpressNews Staff

University of Alberta news release

January 9, 2006

University of Alberta research that rewrites the history of glacial movement in northwestern North America over the past 10,000 years offers important clues to climate change in recent millennia.

Glacier fluctuations are sensitive indicators of past climate change, yet little is known about glacier activity in Pacific North America during the first millennium A.D. Alberto Reyes, a PhD student in the Department of Earth and Atmospheric Sciences, and his research team have found evidence for a regionally extensive glacier expansion during that time, suggesting that climate during the last several thousand years may have been more variable than previously thought. The research appears in the journal Geology.

Reyes and his collaborators – mainly Dr. Dan Smith from the University of Victoria and Dr. Greg Wiles from the College of Wooster in Ohio – looked for a variety of clues in the field to help figure out the timing of past glacier fluctuations. At almost all of the glaciers studied, surface evidence prior to the “Little Ice Age” had been destroyed because glacial advance during that time had been so dramatic. Most of the evidence they found was in the form of buried soils and logs covered by glacial sediments.

“In some cases, entire forest stands were buried by sediments, and their trunks sheared off by advancing ice,” said Reyes, who initiated the work while a master’s student at Simon Fraser University.

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Samples were then sent off for radiocarbon dating, and when the results came back, the researchers were able to determine when each individual glacier was expanding. Reyes had earlier noted a first-millennium-AD advance at the glacier he was studying for his master’s thesis, which jumped out because it was thought glaciers in the region weren’t expanding at that time.

After poring over old data and early results of new research, the team found that many other glaciers had also advanced during that period. “If only one or two glaciers are advancing at any particular time, it is not really significant,” said Reyes. “But when many glaciers across a wide region are advancing with some degree of synchronicity, there is likely something going on with regional climate that causes the glaciers to advance.”

Reyes was surprised that the regional nature of this first-millennium-AD glacier advance remained unrecognized for so long. He suspects that earlier reports hinting at the existence of an advance slipped under the radar because they did not fit into the established chronology of past glacier activity.

The glacier data reported by Reyes and colleagues, together with other clues of past climate, support an emerging idea that climate in the North Pacific region has cycled from warmer to colder intervals several times over the last 10,000 years.

This is a modified news release from the Earth University of Alberta.