Permafrost, or permanently frozen ground – soil, sediment or rock that remains at or below 0° Celsius for at least two continuous years – makes up about 24 percent of the exposed land mass in the Northern Hemisphere: that’s approximately 22.79 million square kilometers. Permafrost can be thousands of years old, or it can be just beginning. Either way, as permafrost thaws, it jeopardizes both man-made structures and natural features. Thawing permafrost on mountain slopes can lead to landslides.
And it’s melting.
Besides posing threats to structures and landscapes on a local scale, melting permafrost emits carbon dioxide and methane, according to the Commonwealth Scientific and Industrial Research Organisation (CSIRO), making permafrost a threat on a global scale.
In a paper published in the most recent issue of Global Biogeochemical Cycles, Dr. Canadell informs that permafrost has the potential to release vast quantities of carbon and methane into the atmosphere, which would only add to the climate change crisis.
“Warmer temperatures at high latitudes are already resulting in unprecedented permafrost degradation,” he says. “Projections show that almost all near-surface permafrost will disappear by the end of this century exposing large carbon stores to decomposition and release of greenhouse gases.” And as the global temperature increases, an irreversible process of thawing could be initiated.
“A number of feedbacks increase the vulnerability of these soils. For example, heat generated from increased microbial activity could lead to sustained and long-term chronic emissions of carbon dioxide and methane.” As the permafrost thaws and melts, ‘thermokarst lakes’ form. These ‘lakes’ are bodies of freshwater, usually shallow, that are formed in depressions by melt-water from thawing permafrost. The formation of such lakes would draw heat to deeper layers and bring methane to the surface.
An increase in fire frequency could also trigger permafrost melt and thermokarst formation.
“The potential for significant feedbacks from permafrost carbon could be realised with only a small fraction of currently frozen carbon released to the atmosphere,” said Canadell. “For example if only 10 per cent of the permafrost melts, the resultant feedback could result in an additional 80 ppm carbon dioxide equivalent released into the atmosphere, equating to about 0.7°C of global warming.”
As the global temperature rises, permafrost melts. As permafrost melts, carbon dioxide and methane are emitted into the atmosphere, causing increases in the temperature. The temperature increase spurs on permafrost thaw, etc., etc. The cycle is vicious and, as Canadell states, could be irreversible.
Are we past the point of no return? Not yet. But action must be taken now to slow or, if possible, stop the melting of permafrost.
Photo Credit: Marina & Enrique via flickr under Creative Commons License