Permafrost is the permanently frozen ground in the coldest regions of the planet. It contains billions of tons of greenhouse gases trapped in the soil at very low temperatures, and experts fear that global warming could change things, transforming the Arctic into a new source of climate-altering emissions. In fact, things seem to be going exactly like this: even if slowly, in recent decades the Arctic permafrost has begun to emit more carbon into the atmosphere than it absorbs.
This was revealed by a study published in the journal Global Biogeochemical Cycles by a team of scientists led by researchers from Stockholm University, who analyzed in great detail the carbon balance of the Arctic regions, i.e. how many greenhouse gases are emitted and how many are instead absorbed every year. The topic is more relevant than ever, given that in the past the Arctic permafrost has always been a so-called “carbon sink”, that is, an ecosystem that stored more carbon than it emitted, thanks to the very low temperatures that prevent the decomposition of the organic matter that forms settles in the frozen ground.
Global warming, however, is changing things: the area covered by Arctic permafrost has already reduced by 7% compared to the 1960s, and it is expected that the entire region will transform into a net contributor in the future, i.e. a source which will contribute to increasing the amount of CO2 and other greenhouse gases in the atmosphere annually, thus amplifying the effects of climate change. To verify the state of affairs, the authors of the new study analyzed measurements taken at over a thousand sites in the Arctic region, obtaining solid estimates of how many greenhouse gases were emitted and absorbed by permafrost between 2000 and 2020.
The results speak clearly: in the twenty years under review, the Arctic permafrost produced 38 million tons of methane, and 670 thousand tons of nitrous oxide (also known as laughing gas), a gas with a very high global warming potential. For carbon dioxide the situation was more difficult to ascertain, because terrestrial ecosystems absorb more than they emit, but only when they are undisturbed: a fire is enough (and they are increasingly common at those latitudes) to change the cards in table.
All things considered, however, the researchers conclude that Arctic permafrost has now already become a net contributor of greenhouse gases, introducing 144 million tons of carbon and 3 million tons of nitrogen into our planet's atmosphere over the past 20 years. Numbers which for now are negligible compared to those of any industrialized country, but which are destined to rise in the future with the further increase in global temperatures, and which could soon transform even the northern regions into an important source of greenhouse gases.