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Research shows that deep layers of frozen soil store ancient carbon and may weaken the natural capacity of cold regions to offset part of human emissions
The melting of permafrost, the permanently frozen soil of cold regions of the planet, may release carbon at a more concerning rate than previously estimated. A new study indicates that deep layers, often underrepresented in climate models, may change the carbon balance in the Northern Hemisphere within this century.
Permafrost is a kind of natural archive formed over thousands of years. Inside it are remains of plants, animals, and microorganisms that were frozen before fully decomposing.
The problem is that, with global warming, this organic material begins to thaw. When this happens, microorganisms resume decomposing the matter trapped in the soil and release greenhouse gases, mainly carbon dioxide and methane.
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The new research does not mean that all this carbon will be released at once. But it indicates that the so-called “carbon bomb” of permafrost may come into action sooner than expected in scenarios of intense warming.
Study points out that deep carbon changes the climate account
According to a study published in the scientific journal Science Advances in June 2026, researchers led by Yi Xi updated simulation models to include deep carbon deposits in permafrost areas. The difference is important because many climate models consider in more detail only the upper layers of soil, generally up to 3 meters deep.
The team worked with an enhanced version of the ORCHIDEE-MICT model, used to simulate interactions between carbon, vegetation, water, and temperature. The goal was to reconstruct how carbon accumulated in ancient deposits, such as the Yedoma soils formed during the Pleistocene, and in peatlands of the Northern Hemisphere.
These deep layers can reach about 10 meters in peatlands and approximately 20 meters in Yedoma deposits, according to information released about the study. By considering this stock, the projection changes significantly.
Instead of continuing to function as a net carbon sink for much of the century, parts of the North may become a net source of CO₂ sooner. In high emission scenarios, the study points to a net release of up to 32 billion tons of carbon by 2100.
Why Permafrost Concerns Scientists So Much
According to information from NASA, permafrost is soil that has remained frozen for at least two years, but it can preserve organic material for tens of thousands of years. When it thaws, this stock is no longer isolated and re-enters the carbon cycle.
The concern is not just about the ice disappearing on the surface. The most sensitive point is that warming deepens the so-called active layer, the part of the soil that thaws seasonally and allows biological activity.
With a deeper active layer, materials previously protected by the cold come into contact with oxygen, water, and microorganisms. This accelerates decomposition and can turn ancient carbon into gases that trap heat in the atmosphere.
The process creates a feedback loop. The planet warms, the permafrost thaws, the soil releases greenhouse gases, and this increase can reinforce the warming.
Boreal Forests Can Help, But Maybe Not Enough
One of the major scientific debates about permafrost involves the role of vegetation. In a warmer world, cold regions may have longer growing seasons, which favors shrubs, trees, and boreal forests.
In theory, more plants mean greater CO₂ absorption through photosynthesis. This gain could offset some of the soil losses, keeping Northern regions as carbon sinks.
The new study, however, reduces confidence in this compensation when deep carbon is considered. Vegetation may grow more, but the soil may also lose carbon in greater volume.
This is a crucial point for climate models. If the models underestimate the carbon hidden in depth, they may also overestimate the natural capacity of these regions to mitigate the climate crisis.
Ancient Carbon Below 3 Meters Was Left Out of Some Projections
According to the National Snow and Ice Data Center, permafrost stores a huge amount of frozen organic matter. Estimates indicate that there is more carbon trapped in these soils than in the current atmosphere.
NOAA also highlights that the permafrost soils of the Northern Hemisphere hold between 1.46 trillion and 1.6 trillion metric tons of organic carbon. A significant portion of this volume is below 3 meters in depth.
This deep carbon is difficult to represent in models because it did not form in just a few decades. It results from long processes of accumulation, freezing, burial, sedimentation, and preservation in very cold environments.
Therefore, the new modeling sought to reconstruct the history of these deposits on scales of thousands of years. The result suggests that previous simplification left out an important piece of the climate puzzle.
Methane increases concern, even though the study focuses on CO₂
The study led by Yi Xi focused the analysis on the CO₂ balance. Even so, permafrost is also associated with methane release, especially in waterlogged areas, thaw lakes, and oxygen-poor soils.
Methane is less long-lasting in the atmosphere than carbon dioxide, but it has greater warming power in short periods. This makes the gas especially relevant for the coming decades.
According to the IPCC, methane emissions associated with wetlands, thermokarst lakes, and permafrost thaw still carry uncertainties but can reinforce climate feedbacks. The warning is that these processes do not act in isolation.
In practice, CO₂ and methane make up two sides of the same problem. The first weighs more in the long term, while the second can intensify warming in shorter time windows.
What changes for global warming projections
The main change is the perception of time. Permafrost was already seen as a climate risk, but the new research suggests that the shift from sink to carbon source could occur decades earlier in high-emission scenarios.
This does not mean that the outcome is inevitable in any trajectory. The most concerning projection is linked to scenarios where global warming advances far above the Paris Agreement target.
The international agreement seeks to limit the increase in global average temperature to 1.5°C above pre-industrial levels, or at least keep it well below 2°C. The more the world exceeds these limits, the greater the pressure on frozen soils tends to be.
The study works with severe warming scenarios up to 2100. If global emissions are strongly reduced, the future behavior of permafrost may be less extreme, although not free from impacts.
Why this warning matters even far from the Arctic
Permafrost thaw seems like a distant problem for tropical countries, but its effects are part of the global climate system. The carbon released in the Arctic mixes with the atmosphere and can influence warming on a planetary scale.
Moreover, the weakening of natural sinks increases the pressure for faster emission cuts. If nature absorbs less carbon than previously thought, the climate safety margin becomes smaller.
The topic also helps explain why scientists insist on improving climate models. It’s not enough to predict average temperature; it’s necessary to represent forests, soils, roots, fires, waters, microorganisms, and deep carbon reservoirs.
The most important conclusion is that permafrost is not just melting ice. It is a huge biogeochemical reservoir, and its behavior can alter the speed at which climate change worsens.
Scientists still see uncertainties, but the risk has become clearer
Despite the warning, the researchers themselves acknowledge that there are still uncertainties. Processes such as abrupt thawing, wildfires, lake formation, soil ice dynamics, and changes in vegetation can alter projections.
This means that the study does not end the discussion. On the contrary, it shows that climate models need to include more details about deep carbon and the quality of frozen organic matter.
The central issue is that uncertainty does not necessarily reduce the risk. In some cases, it may indicate that the impacts have been underestimated.
If permafrost releases more CO₂ sooner than expected, the planet will have less time to avoid accumulated effects. The discussion now is whether governments, companies, and society will treat this warning as just another distant projection or as a sign that the response window is narrowing.
Do you believe that warnings like this can still influence real decisions about climate, energy, and emissions, or does society only react when the impacts hit the wallet and routine? Leave your opinion in the comments, because this is one of those discussions where science points out the risk, but the response depends on political and economic choices.
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