Share of inorganic sources of CO2 during permafrost thawing was unusually high

(ORDO NEWS) — According to scientists, their result is about 20% of the carbon dioxide released during the melting.

Following the melting of permafrost on one of the islands at the mouth of the Lena, climatologists came to the conclusion that a large amount of carbon dioxide is released during this process. Approximately 20% of these emissions come from inorganic sources. The results of the study were published in the scientific journal Frontiets in Earth Science.

Scientists suggest that as a result of the rapid warming of the Arctic, by the end of the 21st century, about a third of the permafrost located in Alaska and southern Siberia will disappear. So far, scientists cannot say exactly how fast organic matter will decompose from thawed permafrost, which does not allow us to assess how this process will affect global warming in the near future.

In a new study, Jan Melchert from the University of Cologne and his colleagues obtained the first such data. They watched the melting and decomposition of permafrost, which formed in the north of Eastern Siberia, on the shores of the island of Kurungnakh at the mouth of the Lena. Its territory is covered with yedoma – a special type of permafrost, which is approximately 50-90% ice.

As a result of melting, porous soil appears on the site of the yedoma, which consists of 2-5.5% of organic remains. It is very vulnerable to microbes, which is why scientists fear that the rapid decomposition of all stocks of yedoma will lead to more than a trillion tons of CO2 and other greenhouse gases entering the Earth’s atmosphere.

Permafrost on Kurungnah Island

Melcher and his colleagues tried to get an answer to this question. They took samples of yedoma from the island of Kurungnah and followed in the laboratory how the organic remains contained in them decompose. Climatologists also collected CO2 samples from thawed permafrost and studied their isotopic composition. This helped to determine the rate of permafrost decomposition, estimate the volumes of greenhouse gases released during this process, and determine the sources of CO2.

It turned out that the ancient organic matter preserved inside the yedoma decomposed very quickly: each square meter of the island’s soil emitted 2-12 grams of carbon dioxide daily. At the same time, scientists found that soil microbes destroyed a significant part of the reserves of ancient and young organic matter in the first year and a half after the permafrost thawed.

In turn, the isotopic composition of CO2 emissions indicated that a significant proportion, about 20% of the total volume, arose as a result of reactions between inorganic carbon compounds. This came as a surprise to climatologists, as previously this source of CO2 was not taken into account when assessing the potential contribution of permafrost melting to global warming.

Such results, according to Melchert and his colleagues, suggest that the process of thawing and decomposition of permafrost in Siberia and other regions of the Arctic will have a much stronger effect on the Earth’s climate than climatologists thought in the past. This must be taken into account when making forecasts for climate change in the Arctic on the whole planet as a whole, the scientists concluded.

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