The most pervasive human fear is the fear of the unknown. One of the things we know very little about, unfortunately, is what lies inside the frozen layer of the tundra known as the permafrost. Long thought to be permanently frozen, it’s now melting much more rapidly than we ever thought, reported NASA scientists in a study in The Cryosphere on Tuesday. A lot of the stuff that lies within it, they warn, will be released within the next few decades.

Of course, they’re not completely clueless about what’s trapped there. Their paper concerns the massive stores of carbon they know lurk deep in the frozen layers of the tundra, trapped there years ago as leaves and other organic material that never decayed. The tundra covers some 5.5 percent of the Earth’s surface, and at the rate the permafrost is thawing due to climate change, they write, the amount of atmospheric carbon that gets released over the next 300 years will be 10 times the amount of carbon we put into the air in 2016. This, of course, will only make climate change worse.

There is one small, encouraging caveat: Not all of the world’s permafrost will release carbon at the same rate. The permafrost in southern Alaska and southern Siberia may already be melting, the researchers write, but the model they created for the study showed that this region won’t really start releasing its carbon until the end of the 2100s. Even more unexpectedly, the permafrost even farther north — where it’s much colder — is expected to release its carbon sooner, even though it is still mostly frozen now.

Accelerated rates of permafrost melt will release long-frozen carbon sooner than we expect, says NASA.
Permafrost melting on Alaska's North Slope, which is expected to become a permanent source of carbon before 2100.

In a statement released on Tuesday, lead author Nicholas Parazoo of NASA’s Jet Propulsion Laboratory, noted his team’s surprise at this finding: “Some of the very cold, stable permafrost in the highest latitudes in Alaska and Siberia appeared to be sheltered from extreme climate change, and we didn’t expect much impact over the next couple hundred years.” But sure enough, it’s this permafrost in the frigid northern Arctic that scientists will be most worried about in our lifetimes. They note the peak transition — when its northerly position on the globe ceases to protect it from the Earth’s rising temperature — could occur in the next 40 to 60 years.

north slope alaska NASA
NASA's Earth Observatory captured this image of Alaska's rapidly thawing North Slope in 2010.

Their unexpected finding that warmer, more southerly regions of permafrost will release carbon more quickly than the north can be explained by its relative closeness to plant growth in more temperate regions. Plants are key to limiting the effects of climate change because they sop up carbon dioxide from the air through photosynthesis, and as the planet warms, the one small upside is that plants will be able to grow further north than before. The plants are expected to be able to stave off the worst effects of carbon release from the permafrost until the late 2100s.

Carbon seems like it will be the biggest of the problems to be released from deep within the Earth as climate change worsens, but it’s not the only thing lurking in the permafrost. Nuclear waste, ancient viruses, and dead bodies will all likely emerge over time, though none are quite as scary as the carbon dioxide and methane that we can’t see.

Bill Nye predicts the future of the environment: