On the trail of the Arctic’s carbon time bomb
Not good for climate (Image: NASA)
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ON A July afternoon in the eastern Siberian town of Cherskiy, 220 kilometres north of the Arctic circle, it is a warm 27 °C. The vista features silver-blue rivers bisecting green swathes of boreal forest – Earth’s biggest ecosystem. But drive a metal rod into the soil and roughly 75 centimetres below the surface you hit a layer that’s as hard as steel – and perhaps as dangerous as dynamite.
Arctic permafrost holds more than twice as much carbon in its frozen soil as Earth’s atmosphere. Which is what brings me here, accompanying seven US scientists from various labs, led by the Woods Hole Research Center in Falmouth, Massachusetts. We have travelled 7000 kilometres and 15 time zones to Cherskiy to study a phenomenon that might hasten the release of that carbon: the rise of Arctic wildfires.
“Welcome to Cherskiy,” our host Nikita Zimov says minutes after we disembark the Antonov-24 propeller plane that brought us here. Zimov directs the Northeast Science Station. “I understand you want me to take you to that hellhole,” he says as he points to a ghost of a forest that will soon enchant the scientists, despite its bugs, muck and fallen trees.
The trees at Hellhole – the moniker sticks – were burned a decade ago and could provide an important clue in the debate over the impact of Arctic fire (see diagram). There is no question that warmer temperatures, drier conditions and, possibly, an uptick in lightning are catalysing a rise in blazes across the Arctic. This summer over 9 million hectares of forest in Alaska and Canada have burnt – a record – drawing thousands of firefighters to help.
Fires devour the organic layer of leaf litter and shrubs on the floor of boreal forests and tundra alike. As this layer offers insulation during the summer, burned sites could see an increase in the depth of the soil that thaws in summer, before refreezing in winter. More thawed soil could mean more microbial respiration of ancient Arctic carbon into the atmosphere, eventually turning the boreal forest from a carbon sink into a source.