Buried Stumps Emerge as Glaciers Retreat Due to Global Warming, Says Geological Association of America

Tree stumps long buried under advancing Canadian glaciers are seeing the light of day for the first time in 7,000 years as the climate warms, according to news from the Geological Society of America (GSA).

Johannes Koch, a geologist at The College of Wooster, discovered what appeared to be fresh tree stumps beyond the retreating edge of glaciers in Garibaldi Provincial Park near Vancouver in British Columbia. In fact, the stumps were still rooted in soil in their original positions.

After radiocarbon-dating wood from the stumps, though, Koch discovered the fresh-looking stumps were actually 7,000 years old.

"The stumps were in very good condition sometimes with bark preserved," said Koch, who carried out the research while working on his doctoral thesis at Simon Fraser University in Burnaby, British Columbia. "Thus they really indicate when the glaciers overrode them, and their kill date gives the age of the glacier advance."

While glaciers around the world have both advanced and retreated over the past 7,000 years, the pristine nature of the stumps in Canada indicate the ice there has never shrunk so far back before during that time period.

Koch compared the ages of the stumps in Canada to those found near glaciers in the Yukon Territory, the Alps, New Zealand and South America. He also examined how the stump ages related to similarly well-preserved wood found in Scandinavians glaciers and snowfields, as well as to the age of Oetzi, the famously mummified "Iceman" discovered in 1991 in a glacier in the Oetzal Alps between Italy and Austria.

Radiocarbon dating showed all the compared samples appeared to be about the same age.

Koch said his findings indicate that human-caused climate change is driving rapid shifts in natural systems.

"It seems like an unprecedented change in a short amount of time," he said. "From this work and many other studies looking at forcings of the climate system, one has to turn away from natural ones alone to explain this dramatic change of the past 150 years."

Koch was scheduled to present the results of his research during the GSA's annual meeting in Denver this week.

Geological Society of America, "Western Canada's Glaciers Hit 7,000-Year Low." URL: (http://www.geosociety.org/news/pr/07-61.htm)