Earth’s permafrost could soon release hidden ‘deep carbon,’ supercharging warming

Earth’s permafrost could soon release hidden ‘deep carbon,’ supercharging warming

Melting permafrost is releasing carbon into the atmosphere, but scientists may have underestimated just how bad the situation may be, a new analysis finds

Permafrost, or frozen soil, covers some 15 percent of land in the Northern Hemisphere, and thanks to human-driven climate change, it is fueling a vicious warming feedback loop. As rising global temperatures melt the frozen soil, it releases stored carbon into the atmosphere, enhancing warming. Scientists have debated for years how fast this could happen and how much carbon the world’s permafrost might expel, but according to a new study , the situation might be far worse than past estimates suggest.

We know that permafrost stores a massive amount of carbon: In the Northern Hemisphere, it holds around double the carbon that’s already in the atmosphere, according to the National Oceanic and Atmospheric Administration. For thousands of years, permafrost has been a reliable carbon “sink”—meaning it has trapped carbon—mostly in the form of frozen organic matter such as dead plant and animal material. Because of warming, northern permafrost could soon release more carbon than it stores, turning it into a carbon source.

In the new study, researchers estimate that that tipping point could happen by 2100—earlier than previous models suggest.

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The reason has to do with frozen soils deep below the surface. While other projections have largely focused on permafrost near the surface, where most of the carbon is stored, the new study accounts for deeper soils. These soils lie beyond a depth of three meters, or about 10 feet, explains Yi Xi, the study’s first author and a postdoctoral researcher at the Laboratory for Climate and Environmental Sciences in France. The results suggest that these deeper soils may be an overlooked source of carbon.

“In our model, we constructed the accumulation history of soil carbon below three meters,” Xi says, such as peatlands that formed during the Holocene. Then, using various global warming scenarios projected by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), she and her co-authors found that without a reduction in global temperatures, melting northern permafrost could emit much more carbon before the end of the century than previously thought.