Permanent permafrost

A researcher ignites methane escaping from Arctic permafrost

Good climate news for a change:  man-made warming of the Arctic’s icy soils may be ten times less deadly than previously thought.

Scientists have been worried that Arctic permafrost – soil that remains frozen all year round – will release large amounts of methane if it’s melted by global warming.  Methane is a greenhouse gas 25 times as powerful as carbon dioxide and a large-scale release could trigger rapid warming of the atmosphere, with dire consequences for life on Earth.

However, a team of European researchers suggests that current predictions of how much methane will escape this century are ten times over the top.

Conventional wisdom has it that when permafrost melts, the soil collapses and meltwater forms lakes in the resulting hollows.  The lake prevents the soil from refreezing and methane – formed during the breakdown of dead plants and animals – is free to bubble into the air. But new research, published in this month’s Nature Climate Change journal, suggests that the meltwater will drain away, rather than pooling in lakes.  With the water gone, a cold snap can refreeze the soil and the methane will become trapped again.

The scientists from Sweden, Russia and the Netherlands modelled a thaw lake area in northern Siberia.  They tested their calculations against sediment records of lake formation, then projected the scenario forward 100 years, using warming data from the Intergovernmental Panel on Climate Change (IPCC).

The model showed that, despite thawed area increasing by up to 25%, after 70 years, lake drainage would allow refreezing.  In fact, after 100 years, the thawed area was projected to be around 6% smaller than the present day.

It’s not all good news though, according to the researchers.  “Lake expansion on the scale predicted by our model will still profoundly affect permafrost ecosystems, including wildlife habitats and human infrastructure,” they say.

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