Permafrost matters because it locks away roughly 1,500 gigatons of organic carbon, nearly twice what’s currently in the atmosphere. As it thaws, that carbon enters the air as carbon dioxide and methane, accelerating climate change. But the climate impact is only part of the story. Permafrost also holds up roads and buildings across the Arctic, preserves ancient pathogens, and supports the way of life of millions of people living in northern regions.
A Massive Carbon Freezer
Permafrost is ground that stays frozen for at least two consecutive years. It covers about 14 million square kilometers, roughly 15% of the Northern Hemisphere’s exposed land surface. Much of it has been frozen for thousands of years, and during that time it has accumulated enormous quantities of dead plant and animal material that never fully decomposed. The cold essentially hit pause on decay.
The estimated 1,500 gigatons of carbon trapped in this frozen ground dwarfs annual human emissions, which currently sit around 10 gigatons per year. As long as the ground stays frozen, that carbon stays locked in place. The concern is what happens when it doesn’t.
How Thawing Drives Climate Change
When permafrost thaws, microorganisms wake up and begin breaking down organic material that has been preserved for millennia. The gases they produce depend on conditions. In the presence of oxygen, decomposition primarily releases carbon dioxide. In waterlogged, oxygen-poor environments like flooded soils or lake bottoms, the process can produce methane, a greenhouse gas with far greater short-term warming power than CO2.
Research on ancient permafrost deposits in Arctic Siberia found that greenhouse gas emissions after thawing were dominated by carbon dioxide, with methane playing a smaller role. In that case, the low methane output was traced to the absence of methane-producing microorganisms in those particular deposits. Other sites, especially those with standing water, can produce significantly more methane. The mix varies by location, but both gases contribute to warming.
This creates the potential for a feedback loop: warming temperatures thaw permafrost, which releases greenhouse gases, which drive more warming, which thaws more permafrost. Scientists have studied past warm periods to understand whether this feedback has ever spiraled out of control. During an exceptionally warm period roughly 400,000 years ago, atmospheric CO2 and methane levels did not spike beyond their normal range, suggesting that widespread thawing in the past didn’t trigger a runaway greenhouse effect. That’s somewhat reassuring, but today’s rate of warming is far faster than anything in the geological record.
Billions in Infrastructure Damage
Across the Arctic, roads, pipelines, airports, and buildings sit on ground that was stable precisely because it was frozen solid. As that ground thaws, it loses its structural integrity. Water trapped in the soil expands and contracts unevenly, causing the surface to buckle, crack, and sink. In Alaska, houses are visibly tipping to one side, and both old and new roads develop large cracks as the ground beneath them shifts. Snow and water pooling along roadsides accelerates the problem by warming the permafrost underneath.
The financial toll is staggering. Recent projections estimate that building and road damage from permafrost thaw could cost Alaska alone between $37 billion and $51 billion, depending on how aggressively global emissions continue. Those figures represent a doubling of earlier estimates, driven by improved mapping that revealed more infrastructure sitting on vulnerable ground. Across the broader Arctic, which includes parts of Russia, Canada, and Scandinavia, the total costs will be far higher.
Risks From Ancient Pathogens
Permafrost doesn’t just preserve carbon. It also preserves microorganisms, including dangerous ones. In 2016, an anthrax outbreak on Russia’s Yamal Peninsula killed thousands of reindeer and sickened dozens of people. It was the region’s first outbreak in 70 years. The trigger was a summer heat wave that thawed permafrost deep enough to expose the carcasses of animals that had died of anthrax decades earlier. The bacterial spores, preserved in the frozen ground, became active again.
Genetic analysis confirmed that the anthrax strains from the Yamal outbreak closely matched strains previously isolated from permafrost in another part of Siberia, supporting the hypothesis that the thaw revived old bacteria rather than introducing new ones. The risk isn’t limited to anthrax. Permafrost can preserve viruses and bacteria for centuries or longer, and as warming deepens the thaw layer each summer, previously buried biological material becomes increasingly exposed.
Reshaping Arctic Landscapes
When ice-rich permafrost melts, the ground collapses and fills with water, forming what scientists call thermokarst lakes. These lakes are appearing across the Arctic at increasing rates, and they create a self-reinforcing cycle of their own. The water stores heat and transfers it to the surrounding frozen ground, accelerating thaw well beyond the lake’s edges. This process reshapes entire landscapes, turning what was once solid, relatively flat terrain into a patchwork of ponds, sinkholes, and eroded gullies.
These changes ripple through local ecosystems. Soil chemistry shifts. Drainage patterns change, drying out some areas while flooding others. Vegetation communities transform as wet-adapted species replace those suited to drier, frozen ground. Caribou migration patterns shift as the terrain they’ve traveled for generations becomes impassable or unrecognizable. The biological processes in the soil itself change, both in the thawed ground around thermokarst lakes and within the lake water.
Consequences for Arctic Communities
For Indigenous peoples across the Arctic, permafrost isn’t an abstract climate concern. It is the foundation of daily life. Thawing ground causes homes to sink and tilt. Erosion threatens entire coastal villages. But the effects go well beyond buildings.
As permafrost degrades, overland travel becomes difficult or dangerous. Routes that were once reliably frozen are now riddled with gullies and unstable ground, limiting access to hunting and fishing areas that communities have depended on for generations. Caribou and whale populations are shifting their migration patterns in response to changing conditions, reducing harvest levels in some regions. Thawing also mobilizes industrial contaminants that were previously locked in frozen soil, sending them into streams and waterways that communities rely on for drinking water and food.
Pamela Miller, executive director of Alaska Community Action on Toxics, has described what she hears from elders in affected communities: permafrost thawing is causing subsidence and erosion around homes while simultaneously limiting access to traditional food and water sources and disrupting travel for hunting and fishing. The effects are interconnected, compounding in ways that threaten both physical safety and cultural continuity.