In western CanadaMelting ice has 'provided' us with frozen mammoths and even frozen people, like the famous Oetzi from the Alps, as if they were kept in a fridge. No wonder that melting glaciers in Western Canada, which recently reached a historic minimum, have unveiled 7,000-year-old tree stumps.
The prehistoric tree stumps were left behind by the retreating melting glaciers in Garibaldi Provincial Park, some 40 mi (60 km) north of Vancouver, British Columbia. The age of the stumps was determined through radiocarbon dating, and the trees appeared to have lived at the end of the ice age.
"The stumps were in very good condition, sometimes with bark preserved," said Johannes Koch of The College of Wooster in Ohio, who based his doctoral thesis (published on Oct. 31 at the Geological Society of America annual meeting in Denver) at Simon Fraser University in Burnaby, British Columbia on this discovery.
The life time of these trees also shows the age of the local glaciers. "The pristine condition of the wood can best be explained by the stumps having spent all of the last seven millennia under tens to hundreds of meters of ice. All stumps were still rooted to their original soil and location. Thus they really indicate when the glaciers overrode them, and their kill date gives the age of the glacier advance. The recently warming climate released the stumps from their icy tombs," said Koch.
Koch made a comparison between the death time of these trees and others encountered in the Canadian southern and northern Coast Mountains of British Columbia and the mid- and southern Rocky Mountains to similar findings from the Yukon Territory, Alps, New Zealand and South America. The age of the Canadian fossil trees matched that of Oetzi, the "Iceman" found in a glacier between Italy and Austria, and similarly well-preserved trunks from Scandinavian glaciers. "The radiocarbon dates seem to be the same around the world," said Koch.
In the last 7,000 years, glaciers experienced variations, but no retreat was so advanced upstream to expose the fossilized ice-preserved stumps. These ancient tree stumps just emphasize the sever glacier retreat started in the last 100 years. "It seems like an unprecedented change in a short amount of time. 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 added.