From: Allison Winter, ENN
Published February 25, 2013 01:56 PM

Siberian Stalactites and Stalagmites Suggest Permafrost Thawing

One of the greatest concerns of global warming is the effects temperature will have on snow and icecaps. With Arctic ice melt, many scientists predict sea levels rise, affecting coastlines and populations around the world. Not only will warmer temperatures affect ice caps, but according to a new study the thawing of permafrost in colder regions could eventually lead to the release of 1,000 giga-tonnes of greenhouse gases into the air which has the potential to further accelerate global warming.

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Scientists lead by a team from Oxford University studied stalactites and stalagmites from northern caves where the ground is permanently frozen in a layer tens to hundreds of meters thick. Because stalactites and stalagmites only grow when liquid rainwater and snow melt drips into the caves, these formations have recorded decades of changing permafrost conditions, providing insight to researchers who can compare past weather conditions to today.

Evidence from Siberian caves suggests that a global temperature rise of 1.5 degrees Celsius (2.7 degrees Fahrenheit) could see permanently frozen ground thaw over a large area of Siberia, threatening release of carbon from soils, and damage to natural and human environments.

'The stalactites and stalagmites from these caves are a way of looking back in time to see how warm periods similar to our modern climate affect how far permafrost extends across Siberia,' said Dr Anton Vaks of Oxford University's Department of Earth Sciences, who led the work. 'As permafrost covers 24% of the land surface of the Northern hemisphere significant thawing could affect vast areas and release giga-tonnes of carbon.

'This has huge implications for ecosystems in the region, and for aspects of the human environment. For instance, natural gas facilities in the region, as well as power lines, roads, railways and buildings are all built on permafrost and are vulnerable to thawing. Such a thaw could damage this infrastructure with obvious economic implications.'

Data from the Ledyanaya Lenskaya Cave — near the town of Lensk, showed that stalactite growth occurred about 400,000 years ago, during a period with a global temperature 1.5 degrees Celsius higher than today. Periods when the world was 0.5-1 degrees Celsius warmer than today did not see any stalactite growth in this northernmost cave. Therefore the data suggests that around 1.5 degrees Celsius is the 'tipping point' at which the coldest permafrost regions begin to thaw.

A report of the research, entitled 'Speleothems reveal 500 kyr history of Siberian permafrost', was published last week online in Science Express.

Continue reading at the University of Oxford.

Ice image via Shutterstock.

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