15% of the Northern Hemisphere is covered by Arctic permafrost
The perennially icy terrain that covers 15% of the Northern hemisphere has become a net emitter of greenhouse gases. Arctic permafrost, melting as a result of global warming, is releasing more methane (CH4) and nitrous oxide (N2O) into the atmosphere than it can absorb, while the balance is still substantially equal for carbon dioxide (CO2).
It is the result of the first scientific assessment of the greenhouse gas balance conducted on the entire Arctic region. Very important data because they give the most precise measure so far – even if the uncertainty margins remain high – of the exchange of the main greenhouse gases at those latitudes. But above all the study manages to quantify the role of global warming in both its main aspects: the fusion of the arctic permafrost, which favors the release of greenhouse gases, and the increase of vegetation, which increases the absorption of CO2.
The Arctic permafrost contains twice the carbon present in the atmosphere today, and in the last 50 years its extent has already been reduced by 7%. Many recent studies claim that limiting the global temperature to +1.5 ºC in the pre-industrial era will slow this phenomenon but will not stop it. Knowing the real net emissive balance, therefore, is fundamental to determining if the Arctic is a “climate bomb” that could explode even in the best emissive scenario. And understand how many greenhouse gases could be released, affecting the breadth of our carbon budget for the Paris Accord goals.
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The study, recently published in Global Biogeochemical Cycles, concludes that the net balance is positive for both methane and N2O. The analysis was carried out from a database that collected field measurements between 2000 and 2020. In these 20 years, the Arctic permafrost has emitted on average every year 12 million tons (Mt) of carbon from CO2, 38 Mt of carbon from methane and 0.67 Mt of nitrogen from nitrous oxide. By subtracting from these values the removals and also including the lateral flows of greenhouse gases (which depend on changes in the surface of ecosystems and exchanges between ocean and land), the permafrost emerges as a net emitter. The final balance is +144 Mt of carbon and 3 Mt of nitrogen each year.