The carbon dioxide that came from the cold

A team from the Earth and Space Sciences Department at the University of Washington (Seattle) proposes to re-evaluate the organic carbon content of soils at very high latitudes up sharply.


Sudha Brown

While stocks have so far been estimated at 1 billion tonnes in the peripheral area of ​​the Arctic Desert and 17 million in the Arctic Desert itself, Ronald Sletten and his colleagues suggest 8,7 and 2,1 billion tonnes respectively. for these two areas.

They are based on the results of fieldwork carried out over three successive summers over an area of ​​365 km2 in the North-West of Greenland.

Unlike previous studies, the permafrost samples analyzed were not limited to the surface part of the soil (the first 25 cm), but were taken to a depth of one meter.

The researchers then was surprised to see the presence of high concentrations of organic carbon in the lower horizons of the soil.
According to them, this carbon burial is due to a phenomenon of “cryogenic mixing”.

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Admittedly, the sector studied represents only a little more than 0,01% of the surface area of ​​the polar zones concerned on a global scale. But if the validity of the extrapolation made by Dr. Sletten's team is confirmed, the melting of permafrost would produce, by massive release of greenhouse gases, a positive feedback much more dramatic than expected on global warming.

This work was presented at the fall session of the American Geophysical Union (San Francisco, December 5-9).


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