Global Warming

Global warming is reshaping Arctic landscapes

Wide tears in the ground, tilted telephone poles and the whiff of rotten eggs in fresh air are warning signs of a carbon “time bomb” as permafrost in Sweden’s thaws. Global warming is happening in these parts three times faster than in the rest of the world.

Permafrost — defined as soil that stays frozen year-round for at least two consecutive years—lies under about a quarter of the land in the Northern Hemisphere. In Abisko, the permafrost beneath the mire can be up to tens of metres thick, dating back thousands of years. In parts of Siberia, it can go down over a kilometre and be hundreds of thousands of years old. With average temperatures rising around the Arctic, the permafrost has started to thaw. As it does so, bacteria in the soil begin to decompose the biomass stored within. The process releases the greenhouse gases carbon dioxide and methane.

Between carbon dioxide (CO2) and methane, permafrost contains some 1,700 billion tonnes of organic carbon, almost twice the amount of carbon already present in the atmosphere. Methane lingers in the atmosphere for only 12 years compared to centuries for CO2 but is about 25 times more potent as a greenhouse gas over a 100-year period.

So when will the permafrost reach a tipping point? That is, a temperature threshold beyond which an ecosystem can tip into a new state and risk disturbing the global system. It’s feared, for example, that the Amazon tropical forest could turn into a savannah or that the ice sheets atop Greenland and West Antarctica could melt entirely.

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