Melting permafrost is bad because it triggers a cascade of environmental problems, from releasing massive amounts of stored carbon into the atmosphere to destabilizing the ground beneath roads, buildings, and entire communities. Permafrost, the permanently frozen ground that covers about a quarter of the Northern Hemisphere’s land surface, has kept roughly 1,460 to 1,600 billion metric tons of organic carbon locked away for thousands of years. That’s about twice the amount of carbon currently in the atmosphere. As global temperatures rise, this frozen ground is thawing, and the consequences stretch far beyond the Arctic.
A Massive Carbon Reserve Is Unlocking
The most alarming thing about thawing permafrost is the sheer volume of carbon it holds. Over tens of thousands of years, dead plants and animals were buried and frozen before they could fully decompose. That organic material has been sitting in cold storage, essentially removed from Earth’s carbon cycle. When permafrost thaws, microbes wake up and start breaking down that material, releasing carbon dioxide and methane into the atmosphere.
Carbon dioxide is the primary gas released by weight, but methane matters too because it traps far more heat per molecule. Even relatively small methane releases from thawing soils can meaningfully accelerate warming. Research from the Proceedings of the National Academy of Sciences shows that Arctic ecosystems are projected to shift from absorbing carbon to emitting it before 2100, as the warming-driven release of stored carbon overtakes the ability of northern plants to pull carbon from the air through photosynthesis.
The Feedback Loop That Speeds Up Warming
What makes permafrost thaw particularly dangerous is that it creates a self-reinforcing cycle. Rising temperatures thaw permafrost, which releases greenhouse gases, which raise temperatures further, which thaws more permafrost. This is known as the permafrost carbon feedback, and it operates independently of human emissions. Even if the world cut fossil fuel use dramatically, permafrost that has already begun thawing would continue releasing carbon for decades.
Under the most extreme warming scenario modeled by the IPCC, up to 93% of near-surface permafrost could disappear by 2100 compared to preindustrial levels. Even under more moderate projections, roughly 77% of near-surface permafrost is expected to be lost by the end of the century if surface air temperatures rise by about 13.5 degrees Fahrenheit. Each percentage point lost adds more carbon to the atmosphere, making climate targets harder to reach.
Billions in Infrastructure Damage
Permafrost acts as a foundation. Roads, pipelines, airstrips, and buildings across the Arctic were built on ground that was assumed to stay frozen. As it thaws, the ground becomes soft and uneven, causing structures to crack, tilt, and sink. In Alaska alone, building and road losses from permafrost thaw are projected to cost between $37 billion and $51 billion under medium to high emissions scenarios, roughly double what earlier estimates suggested.
The damage isn’t gradual in the way most people imagine. When ice-rich permafrost melts, the ground can collapse suddenly, forming sinkholes and uneven terrain. These features, called thermokarst, reshape entire landscapes. Lakes form in collapsed areas, and because water stores and transfers heat efficiently, these new lakes accelerate thawing of the surrounding permafrost. Lakes deeper than about 2.5 meters can thaw the ground all the way down to the permafrost base, creating permanently thawed zones that never refreeze.
Arctic Coastlines Are Crumbling
Permafrost holds Arctic coastlines together. As it thaws, waves carve into the softened ground, and shorelines retreat. On average, Arctic coasts lose about half a meter (1.6 feet) per year. But some areas are losing ground far faster. In northern Alaska, the average rate is 1.4 meters (4.6 feet) per year, and hotspots like Drew Point, Alaska, have seen erosion of up to 20 meters (66 feet) in a single year. Similar rates of 10 to 20 meters per year have been documented along the Canadian Beaufort Sea and on Muostakh Island in Russia’s Laptev Sea.
This erosion doesn’t just redraw maps. It washes sediment, nutrients, and contaminants into coastal waters, altering marine ecosystems. It also destroys the land that coastal communities depend on for housing, transportation, and access to hunting and fishing grounds.
Mercury Entering Rivers and Food Chains
Permafrost stores more than carbon. Arctic soils hold an estimated 1,656 gigagrams of mercury in the top three meters, with roughly 793 gigagrams locked in the frozen layer itself. As permafrost thaws, that mercury enters rivers and eventually reaches oceans, where it can accumulate in fish and work its way up the food chain to humans.
Research published in Nature Communications projects that under a high emissions scenario, annual mercury releases from thawing permafrost could rival current global human-caused mercury emissions by 2200. In a more immediate timeframe, mercury concentrations in the Yukon River are projected to double by 2100 under high emissions, with corresponding increases in fish contamination. Under a low emissions pathway, the increases are smaller, around 14%, highlighting how much the outcome depends on the trajectory of global warming.
Threats to Indigenous Communities
The people living closest to thawing permafrost are already feeling its effects. Indigenous communities across the Arctic depend on frozen ground for stable housing, clean water, safe travel routes, and access to traditional food sources like caribou and whales. Thawing permafrost undermines all of these. Subsidence and erosion damage homes. Long-frozen industrial pollutants are being released into drinking water and traditional food sources. Changing conditions have shifted the migration patterns and population sizes of key species, reducing harvests in some areas.
Some communities have already been forced to move. Residents of Niugtaq, Alaska, were relocated further inland because of flooding and land loss driven by climate change. Relocation is enormously disruptive, both practically and culturally, for communities with deep ties to specific landscapes. And as permafrost continues to thaw, more relocations will follow.
Ancient Microbes Coming Back to Life
Permafrost has also preserved microorganisms for thousands of years, and some of them are still viable when thawed. Researchers have revived thirteen previously unknown viruses from Siberian permafrost samples, all of which remained infectious. The oldest, a virus called Pandoravirus yedoma, had been frozen for 48,500 years. In 2018, microscopic worms were recovered alive from Siberian soil where they had been frozen for 42,000 years.
The viruses revived so far infect amoebas, not humans. But scientists have noted that the same permafrost layers contain preserved animal remains, including wolf organs and mammoth wool, suggesting a rich microbial ecosystem locked in the ice. Whether future thawing could release microbes capable of infecting humans remains uncertain. The 2016 anthrax outbreak in Siberia, linked to a thawed reindeer carcass, demonstrated that the risk of old pathogens re-emerging is not purely theoretical. The concern is less about any single virus and more about the unpredictability of what a warming Arctic might release from its deep freeze.