Permafrost Becoming a Carbon Source Instead of a Sink


As global and regional warming continues, winter emissions of carbon dioxide from Arctic lands are offsetting what plants absorb in the summer.

Winter carbon emissions from Arctic regions appear to be adding more carbon to Earth’s atmosphere each year than is being taken up by Arctic plants and trees. It is a stark reversal for a region that has captured and stored carbon for tens of thousands of years.

In a study published in Nature Climate Change, scientists estimated that 1.7 billion metric tons of carbon were lost from Arctic permafrost regions during each winter from 2003 to 2017. Over the same span, an average of 1 billion metric tons of carbon were taken up by vegetation during summer growing seasons. This changes the region from being a net “sink” of carbon dioxide—where it is captured from the atmosphere and stored—into being a net source of emissions.

Permafrost is the carbon-rich frozen soil that covers about one quarter of Northern Hemisphere land area; it encompasses vast stretches of Alaska, Canada, Siberia, and Greenland. Scientists have estimated that permafrost stores more carbon than has ever been released by humans via fossil fuel combustion. These frozen soils have kept carbon safely locked away for thousands of years, but rising temperatures are making them thaw and release those greenhouse gases.

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Image via NASA Earth Observatory