As the Arctic rapidly warms, permafrost – perennially frozen soil – is thawing fast. As ground temperature climbs above freezing, microbes break down organic matter in soil, releasing greenhouse gases that accelerate global warming. Permafrost soils hold twice as much carbon as the atmosphere: 1,600 billion tonnes.
Current climate models assume that permafrost gradually thaws from the surface downwards. Deeper layers become exposed only over decades or even centuries.
The models ignore that frozen soil doesn’t just lock up carbon – permafrost physically holds the landscape together. Across the polar regions, including boreal forests, permafrost is collapsing suddenly from ice melt. Instead of a few centimeters of soil thawing each year, several meters of soil destabilize within days or weeks. The land sinks and becomes inundated with swelling wetlands and lakes. Forests flood, killing vast stands of trees.
Worse, the most unstable regions are the most carbon rich. Over 1 million square kilometers of Alaska, Canada, and Siberia are larded with Yedoma: thick permafrost deposits from the last ice age. Yedoma is often 90% ice, making it extremely vulnerable to warming. Moreover, Yedoma collectively contains 130 billion tonnes of organic carbon: equivalent to over a decade of the greenhouse gases that human emit in their industrial endeavors.
The warming impact from thawing permafrost is likely to be at least twice that expected from current models.