Riccardo Liguori A new study, published in Nature Climate Change, reveals that over 30% of the Arctic has become a source of CO2 emissions, putting the planet's climate balance at risk. Permafrost, which has stored vast amounts of carbon for millennia, is melting at an accelerating rate, releasing greenhouse gases into the atmosphere
@Virkkala et. al 2025
Just think of a sleeping giant waking up in agony, panting in the heat of fever. It’s today’s Arctic image-ancient ecosystem spanning Siberia through Alaska to Canada-which may just turn out to be one climatic hellhole for the whole world. And a study in Nature Climate Change shows exactly how bad the situation has got.
Permafrost-that allegedly permanent layer of frozen ground that locked away massive amounts of carbon for millennia-are breaking down under the pressure of global warming; as it thaws, it releases greenhouse gases into the atmosphere with potentially disastrous consequences.
For thousands of years, arctic ecosystems-tundra, boreal forests, and wetlands-have played the role of natural carbon sinks, trapping vast amounts of possible emissions within permafrost. But climate change, and particularly one of its dangerous byproducts-wildfires-is rewriting that rulebook.
The numbers speak volumes
Based on monitoring data from 200 sites between 1990 and 2020, the study shows that rapid warming is altering arctic ecosystems, leading to increased carbon dioxide emissions. “this is the first time we’re seeing this shift on such a large scale, cumulatively across the entire tundra,” explains Sue Natali, co-author of the study and researcher at the Woodwell Climate Research Center. “it’s a pretty big deal.”
The study estimates the number of the arctic-boreal zone now a source rather than a sink at more than one-third-34%. What this means is that the Arctic is releasing more CO2 than it absorbs, which is dangerous to the planet’s climatic balance. And it gets even worse when the emissions from wildfires, fueled by rising temperatures, are included. With these included, 40% of the Arctic becomes a carbon source.
Thawing permafrost fuels landscape collapse
“In some areas, such as inland Alaska, when the permafrost thaws, plant growth also increases, sometimes leading to additional carbon storage,” Natali says. “But the permafrost just keeps getting warmer, and then the microbes takeover. You end up having this huge reservoir in the soils that you just see things such as ground collapse- you actually start seeing it, visually see how the landscape’s changing.”
Lead author Anna Virkkala drives the point of the threat home: “There’s a lot of carbon in Arctic soils-almost half of the Earth’s total soil carbon pool. It’s far more than what’s currently in the atmosphere. It’s a massive potential reservoir that ideally should stay in the ground.”
But as temperatures rise, permafrost thaws and makes available organic matter entombed, so it turns out to be ready for microbial decomposition. Thus releasing CO2 to the atmosphere. “This is the permafrost carbon feedback, and it is really the key player here,” said Virkkala.
Natural carbon sinks getting under pressure
It does so at a time when the world’s natural carbon sinks-oceans and forests currently absorbing about half of human emissions-are a growing concern. But with the acceleration of global warming, these carbon sinks are under increasing stress, and their weakening could further accelerate climate change.
