When permafrost melts, what happens to all that stored carbon?

Public Release: 5-Dec-2016
When permafrost melts, what happens to all that stored carbon?
Study shows massive release during past warming spike
The Earth Institute at Columbia University

The Arctic's frozen ground contains large stores of organic carbon that have been locked in the permafrost for thousands of years. As global temperatures rise, that permafrost is starting to melt, raising concerns about the impact on the climate as organic carbon becomes exposed. A new study is shedding light on what that could mean for the future by providing the first direct physical evidence of a massive release of carbon from permafrost during a warming spike at the end of the last glacial period.

The study, published this week in the journal Nature Communications, documents how Siberian soil once locked in permafrost was carried into the Arctic Ocean during that period at a rate about seven times higher than today.

"We know the Arctic today is under threat because of growing climate warming, but we don't know to what extent permafrost will respond to this warming. The Arctic carbon reservoir locked in the Siberian permafrost has the potential to lead to massive emissions of the greenhouse gases carbon dioxide and methane to the atmosphere," said study co-author Francesco Muschitiello, a post-doctoral research fellow at Columbia University's Lamont-Doherty Earth Observatory.

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The new study looks at a parallel process, estimating the change in the amount of carbon released from permafrost by examining the amount of organic carbon that was washed from destabilized permafrost into the Lena River and out toward the Arctic Ocean. When permafrost starts to melt, its top "active layer" deepens and the soil loosens, allowing water to flow through it more easily, releasing greenhouse gases to the atmosphere and washing away stored carbon.

"The results indicate severe deepening of the active-layer permafrost in the watershed and release of previously frozen-lock soil carbon, which also implies enhanced microbial respiration of CO2 with important implications for carbon-climate feedback during climate warming," said lead author Tommaso Tesi, a researcher at the Italian National Research Council. Oceans also release CO2 from organic carbon.

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