Rapidly Melting Permafrost Has Tipped the Arctic Into Being a Net Greenhouse Gas Emitter

Global warming’s disproportionate effect on the planet’s polar regions has turned the Arctic into a net carbon emitter, with one-third of the region’s forests, tundra and wetlands now emitting more greenhouse gases than they absorb as the previously-frozen permafrost thaws.

“It is the first time that we’re seeing this shift at such a large scale, cumulatively across all of the tundra,” according to Sue Natali, an ecologist with the Woodwell Climate Research Center, whose team researched data gathered from over 200 sites around the Arctic between 1990 and 2020. “That’s a pretty big deal.”

According to the study, more than 30 percent of the north’s Arctic-Boreal Zone (ABZ) has become a net source of carbon dioxide—a number that rises to 40 percent when emissions from wildfires are factored in—despite a measured increase in CO2 absorption in regions where plants have begun to grow. It’s that 40 percent that has tipped the ABZ into being a net CO2 emitter, rather than a carbon sink.

“One place where I work in interior Alaska, when the permafrost thaws, the plants grow more so you can sometimes can get an uptick in carbon storage,” Natali explained. “But the permafrost continues to melt and the microbes take over. You have this really big pool of carbon in the ground and you see things like ground collapse. You can visually see the changes in the landscape.”

Hundreds of billions of tons of greenhouse gases, such as carbon dioxide and methane, have been trapped in Arctic permafrost for tens of thousands—and in some regions, millions—of years. Over the past few decades, human-generated global warming has been thawing that permafrost, allowing the greenhouse gases trapped inside to leak into the atmosphere where it traps even more thermal energy, contributing to an ever-accelerating feedback loop that has caused an alarming rise in climate-driven disasters around the world.

“There is a load of carbon in the Arctic soils. It’s close to half of the Earth’s soil carbon pool. That’s much more than there is in the atmosphere. There’s a huge potential reservoir that should ideally stay in the ground,” warns study lead Anna Virkkala.

“As temperatures get warmer, soils get warmer,” Virkkala continues. “In the permafrost, most of the soils have been entirely frozen throughout the full year. But now the temperatures are warmer, there’s more organic matter available for decomposition, and carbon gets released into the atmosphere. This is the permafrost-carbon feedback, which is the key driver here.”