Western Canada's Glaciers Hit 7000-Year Low

Oct 30, 2007
Western Canada's Glaciers Hit 7000-Year Low
Overlord Glacier: 7000 years old. Glacier in background.

Tree stumps at the feet of Western Canadian glaciers are providing new insights into the accelerated rates at which the rivers of ice have been shrinking due to human-aided global warming.

Geologist Johannes Koch of The College of Wooster found the deceptively fresh and intact tree stumps beside the retreating glaciers of Garibaldi Provincial Park, about 40 miles (60 km) north of Vancouver, British Columbia. What he wanted to know was how long ago the glaciers made their first forays into a long-lost forest to kill the trees and bury them under ice.

To find out, Koch radiocarbon-dated wood from the stumps to see how long they have been in cold storage. The result was a surprising 7000 years.

"The stumps were in very good condition sometimes with bark preserved," said Koch, who conducted the work as part of his doctoral thesis at Simon Fraser University in Burnaby, British Columbia. Koch will present his results on Wednesday, 31 October 2007, at the Geological Society of America Annual Meeting in Denver.

The pristine condition of the wood, he said, 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," Koch explained. They also give us a span of time during which the glaciers have always been larger than they were 7000 years ago — until the recently warming climate released the stumps from their icy tombs.

Koch compared the kill dates of the trees in the southern and northern Coast Mountains of British Columbia and those in the mid- and southern Rocky Mountains in Canada to similar records from the Yukon Territory, the European Alps, New Zealand and South America. He also looked at the age of Oetzi, the prehistoric mummified alpine "Iceman" found at Niederjoch Glacier, and similarly well-preserved wood from glaciers and snowfields in Scandinavia.

The radiocarbon dates seem to be the same around the world, according to Koch. It's important to note that there have been many advances and retreats of these glaciers over the past 7000 years, but no retreats that have pushed them back so far upstream as to expose these trees.

The age of the tree stumps gives new emphasis to the well-documented "before" and "after" photographs of retreating glaciers during the 20th century.

"It seems like an unprecedented change in a short amount of time," Koch 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."

Source: Geological Society of America

Explore further: 2014 Antarctic ozone hole holds steady

add to favorites email to friend print save as pdf

Related Stories

Samsung vows changes after mobile profit plunges

29 minutes ago

Samsung Electronics Co. admitted erring in its smartphone strategy and vowed Thursday to overhaul its handset lineup after profit from those devices tumbled last quarter to the lowest in more than three years.

WhatsApp founders own nearly $9B in Facebook stock

39 minutes ago

WhatsApp founders Jan Koum and Brian Acton received 116 million shares of Facebook stock currently worth nearly $9 billion when they sold their unprofitable messaging service to the social networking leader earlier this month.

Student science projects explode with rocket

40 minutes ago

Eighteen groups of students have lost science projects that were onboard an unmanned rocket that exploded in Virginia after taking off for the International Space Station.

Billionaires' $10m gift to Yale stirs debate in China

41 minutes ago

A Chinese billionaire couple's $10 million gift to Yale University sparked controversy among the country's Internet users Thursday, with some arguing that the money would be better spent on schools in China.

Recommended for you

2014 Antarctic ozone hole holds steady

11 hours ago

The Antarctic ozone hole reached its annual peak size on Sept. 11, according to scientists from NASA and the National Oceanic and Atmospheric Administration (NOAA). The size of this year's hole was 24.1 million ...

New study finds oceans arrived early to Earth

14 hours ago

Earth is known as the Blue Planet because of its oceans, which cover more than 70 percent of the planet's surface and are home to the world's greatest diversity of life. While water is essential for life ...

Magma pancakes beneath Lake Toba

14 hours ago

Where do the tremendous amounts of material that are ejected to from huge volcanic calderas during super-eruptions actually originate?

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

mikiwud
not rated yet Oct 31, 2007
Surely,if the trees had been under a glacier for 7000yrs,they would have been worn away or ejected at the moraine by the movement?
GuruShabu
3 / 5 (2) Oct 31, 2007
Who knows that the global warming is due to human influence?
This is the typical distortion of information adding something not related to it.
Global warming is a fact.
Human influence in global warming is speculation. Thus it should be treated as such.
lengould100
not rated yet Dec 05, 2008
And, in your system of logic, will remain speculative until what further proof is provided?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.