What is permafrost? What happens when permafrost thaws? This animation, based on research by scientists at the Alfred Wegener Institute, answers these questions. Understanding this problem, and its connection to global climate change, is of vital importance at a time when the thawing Arctic tundra is creating massive craters and bringing back diseases like anthrax.
What is permafrost and how does it relate to climate change?
Permafrost is soil that has remained below 0C (32F) for more than two years. It occurs in regions where the summer warmth fails to penetrate the ground sufficiently to thaw the soil. These conditions prevail in high-latitude or high-mountain areas that cover roughly a quarter of the Earth’s land surface – including Alaska, Canada and Siberia. The thickness of permafrost ranges from a few metres to many hundreds of metres, depending on the local climate.
Due to climate change, soil temperatures are rising. This can be seen in long-term borehole measurements from different permafrost zones, which show a significant warming trend during the past 30 years. The permafrost layer is thinned by warming, and disappears entirely if the warming is sufficiently great and sustained.
In the near term, thawing permafrost can cause serious local problems – such as damaging or buildings and other infrastructure – but the larger concern around permafrost thaw relates to greenhouse gas emissions.
Permafrost soils are extremely rich in organic carbon. According to one estimate they contain about 1700 billion tonnes of it – about twice the total amount of carbon currently in the atmosphere. When the soil remains deep-frozen, the carbon is largely inert, but when the permafrost thaws, the decomposition of organic matter through microbial activity increases sharply – with the consequence that large amounts of carbon will eventually get respired into the atmosphere as CO2 and (to a lesser extent) methane.
This is an example of a positive feedback loop, because the greenhouse gases released by the thawing permafrost will exacerbate the warming, leading to more permafrost thawing, more warming, and so on. One recent study estimated that about one-tenth of the permafrost carbon pool might get released by 2100 under a scenario with strong future warming – equivalent to around twenty years of man-made CO2 emissions at current rates. More still would be released over subsequent centuries, and the process would not be readily reversible.
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All hell breaks loose as the tundra thaws
Over the past three years, 14 other giant craters have been found in the region, some of them truly massive – the first one discovered was around 50m (160ft) wide and about 70m (230ft) deep, with steep sides and debris spread all around. There have also been cases of the ground trembling in Siberia as bubbles of methane trapped below the surface set the ground wobbling like an airbed. Even more dramatic, setting fire to methane released from frozen lakes in both Siberia and Alaska causes some impressive flames to erupt. (Related: Methane release from melting permafrost could trigger dangerous global warming)
Scientists say a long feared climate ‘feedback’ is now happening
Chris Mooney, The Washington Post
In a massive new study published in the influential journal Nature, more than 50 authors from around the world document a so-called climate system “feedback” that, they say, could make global warming considerably worse over the coming decades. That feedback involves the planet’s soils, which are a massive repository of carbon.
Why trapped methane in the Arctic is a problem for all
Dave Lindorff, Counterpunch
The concern is that if the Arctic Ocean waters were to warm even slightly, as they will do as the ice cap vanishes in summer, at some point the clathrates which have currently trapped massive amounts of methane will suddenly dissolve releasing tens of thousands of gigatons of methane in huge bursts.