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Scientists discover new source of greenhouse gas emissions in Siberian permafrost

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An important part of tackling the climate crisis is understanding what is happening in the Earth’s atmosphere in terms of heating, cooling and the factors that contribute to it. Now scientists have discovered a massive new source of nitrous oxide (NOT2O), one of the greenhouse gases causing the warming of our planet.

This source of nitrous oxide is an abundant type of permafrost called Yedoma, rich in organic matter, spanning over a million square kilometers of land in the northern hemisphere.

Here, the researchers studied the Lena and Kolyma rivers in northeast Siberia.

“Yedoma’s high ice content makes it vulnerable to sudden thaw and soil collapse, allowing rapid mobilization of soil carbon and nitrogen stocks after thaw,” the researchers write in their published paper.

“Along the arctic rivers and coastal area of ​​the arctic continental shelf, the thawing of the Yedoma permafrost creates sheer Yedoma exposures tens of meters high, where many of the conditions known to favor the N2O emissions from soils affected by permafrost are respected. “

Nitrous oxide is produced by microbes in the soil. While the gas is not as abundant as carbon dioxide and methane in the atmosphere, it has a much greater effect in terms of temperature: it is almost 300 times more potent than carbon dioxide as a warming agent over a period of 100 years.

The researchers’ permafrost analysis revealed specific processes in the Yedoma that contributed to such a high N2O output: This is partly related to the rate at which the sediments dry and stabilize after thawing. While nitrous oxide emissions from melting permafrost start slowly, they increase rapidly in less than a decade.

What happens in the ground as it thaws is that the N2The population of O-producing microbes is increasing while the N2The microbial population consuming O is decreasing. This changes the nitrogen cycle and means that a lot more nitrous oxide is expelled.

“Although it is important to remember that such a high N2O emissions will occur in particular contexts … these conditions are not limited to the regressive thaw subsidence along the rivers studied here “, write the researchers.

“Similar disturbed nitrogen-rich Yedoma with successional vegetation cover are prevalent along the thermokarst the shores of lakes, coasts, slopes and valleys of the Yedoma region. “

In other words, the conditions here – the high ice content of the Yedoma exposed to the surface (meaning rapid thaw), the right humidity levels, enough time for microbial populations to move – are likely to be found in many other places. .

Previously, researchers believed that nitrogen trapped inside permafrost was not of particular concern for climate change, as nitrogen cycling in cold arctic soil is typically very slow (N2O emissions generally come from agriculture).

This study shows that much more research needs to be done on how much nitrogen could be stored in these cold landscapes, how quickly it could be released, and what the effects could be on global warming and these ecosystems as a whole.

“The release of nitrogen from thawing permafrost can dramatically improve the availability of nitrogen in arctic ecosystems, which, in addition to direct climate feedback in the form of nitrous oxide, can have important consequences for the environment. carbon fixation by plants and eutrophication of aquatic systems’, says environmental scientist Maija Marushchak, from the University of Eastern Finland.

The research was published in Nature Communication.


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