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October 2008 issue	In this issue Table of Contents Feature: Grise Fiord Feature: Norway Carbon Tax The Inside Story Editor’s Notebook Reverberations À la carte

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The other melting ice cap
Northerners may be on slurry ground as global warming thaws the frozen soil under their feet
By Steven Fick and Elizabeth Shilts

The ground covering almost a quarter of the northern hemisphere is permanently frozen, parts of it more than a kilometre deep. This is the permafrost zone (above), and building on it — especially its ice-rich regions — is an engineering challenge. The design of pipelines, roads and other infrastructure has to account for occasional thaws, slumps and shifts.

Now, slumps are expected to become more frequent and the thawing is deepening. For these frozen lands, which occur in regions of the world where temperatures could rise the most with climate change, the melt may have widespread effects.

Permafrost can range in temperature from below -10°C to just under the freezing point. The entire land base in continuous permafrosted areas is layered with ice, most of which was formed more than 10,000 years ago, during the last ice age.

Over the past few decades, monitoring sites have shown a general increase in permafrost temperatures. But scientists suggest that subarctic North American permafrost, which largely hovers within a couple degrees of its melting point, could see more significant thawing than regions such as the Canadian Arctic, where permafrost is typically colder and thicker. The Intergovernmental Panel on Climate Change also predicts that the extent of permafrost in the northern hemisphere could decrease by some 20 percent by mid-century, and summer thawing depth could increase by about 25 percent.

The resulting slumping could drain lakes, alter shorelines and modify the course of waterways, ultimately reshaping ecosystems. Such changes can affect vegetation, animal migration routes and human infrastructure. Studies have also revealed that melting permafrost around some lakes has released significant amounts of methane — a greenhouse gas that is, volume for volume, 21 times more effective than carbon dioxide in trapping the sun’s heat — and, as a result, could further accelerate global warming.

Canada holds about 30 percent of the hemisphere’s permafrost. Since the late 1990s, climate change and its impacts on permafrost have been factored into major northern development projects, such as the design of the Ekati diamond mine’s waste storage and the design and environmental assessment of the proposed Mackenzie Gas Pipeline. But Canada’s varied northern landscape — from boreal forest to peatlands to tundra to permanent snow and ice cover — make it difficult to predict exactly how increased air temperatures will affect permafrost.

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