Maybe it was a story of researchers finding a frozen baby mammoth in some permafrost.

Or you might have heard about the risk of it melting and releasing some long, dormant supervirus.

But there's a good chance permafrost is not exactly what you picture in your head.

It's not just a layer of ice and snow.

It's the frozen remains of ancient ecosystems.

And in some cases, it's the foundation of modern ones.

It's actually pretty complex, and there are a lot of reasons to care about it.

Because a ton of it is about to melt.

And if it does, it's going to have a massive impact on the entire planet.

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In simple terms, permafrost is soil in the ground that stays frozen year-round for at least two years straight.

But there's so much more to it than that.

While permafrost often includes lots of rock and ice, the key ingredient is organic matter.

So when you hear about animal bodies being found in permafrost, they aren't, like, frozen in an ice cube.

It's more like being mummified in frozen mud.

All that organic matter, and the carbon atoms within it, are what make permafrost so important for the entire planet.

As a plant grows, it takes carbon dioxide out of the atmosphere and stores it in its roots, stalk, and leaves.

When the plant dies and decomposes, a lot of that carbon ends up going right back into the atmosphere as carbon dioxide, or worse, methane.

But what if you stuck that plant in a freezer before it had a chance to decompose?

You'd trap all of its carbon in the freezer, too.

That's why permafrost is a carbon sink, something that pulls carbon out of the atmosphere.

It stops the decomposition process in its tracks.

That is, until it melts.

Once things warm up, microbes break down all that organic matter and release carbon dioxide and methane.

And methane is an even worse greenhouse gas than carbon dioxide because it traps so much more heat.

Over a century, methane warms the planet up to 30 times more than CO2.

You can probably see the issue here.

If the Earth warms up, permafrost melts and releases greenhouse gases that warm the Earth even more, melting more permafrost, and so on.

Even more concerning, Earth's poles are warming about twice as fast as the rest of the planet.

Which is where you can find the vast majority of our permafrost.

There are 14 million square kilometers of it across northern Europe,

Alaska, and the Canadian and Russian Arctic.

Like, you can find permafrost under 15% of the land in the Northern Hemisphere.

And all of that permafrost stores about twice as much carbon as is in our atmosphere today.

There's also some permafrost in the Southern Hemisphere, and even some undersea permafrost, mostly in the Arctic Ocean.

So it's a lot more widespread than you'd think.

Permafrost may evoke an image of barren, lifeless tundra, but that's another misconception.

It can form the base of thriving ecosystems like boreal forests that grow on peatlands.

And plants growing on permafrost are really helpful since they provide insulation and shade to prevent the ice from thawing.

So when a wildfire comes along and burns down all the plants, permafrost ends up melting even after the blaze is out.

Not from the heat of the fire, but from the ground staying warmer without the forest to shade it.

A 2023 study in Alaska looking for hot spots of methane emissions from melting permafrost found that they were nearly a third more likely in areas where wildfires had burned through even 50 years prior.

And a warmer planet means more intense wildfires, which will just keep this cycle going.

By now, you've probably figured out that this is more than just some frozen ground, but permafrost is also more than just one thing.

One of the coolest kinds of permafrost is called yedema, and it's utterly crucial when it comes to carbon storage.

Yedema is a massive permafrost layer that stretches across Siberia, Alaska, and Canada.

It can be up to 130,000 years old, but all of it dates back to the last ice age, so all of it is at least 10,000 years old.

Over the last two centuries, yedema has been the subject of much debate among scientists.

They first used the term to describe permafrost that was particularly rich in ice.

In fact, scientists would find massive chunks of ice buried in the ground next to things like woolly mammoths.

So their question was, how did that ice get there?

It took a hot minute to figure out how these ice wedges formed, but now researchers have a pretty good idea.

In the cold Arctic winter, the ground contracts, forming small cracks across it.

These cracks then fill up with water from melting snow and other runoff, which freezes when it flows down and reaches the cold permafrost.

Water is one of the few substances that expands when it freezes, so the growing ice widens the cracks ever so slightly.

Every year, this seasonal cycle repeats, and the ice wedges grow into massive columns of ice.

From ground level, these look like a network of large polygons, but below this, ice wedges in yedema can be more than 40 meters deep.

In addition to being ice-rich, yedema is also carbon-rich.

See, because it formed during the last ice age, the carbon froze really quickly and didn't have much chance to decompose first.

Not all of this carbon would be released in the atmosphere if the layer melted, but around 10% could be.

And the fact that yedema is perforated by all these ice wedges turns out to have a pretty devastating downside.

When those ice wedges melt, they destabilize the surrounding permafrost.

The ground collapses, creating voids that are now exposed to air, perfect conditions for organic material to decompose and release greenhouse gases.

One computer model suggests that by the year 2300, greenhouse gas emissions from all types of permafrost will be about as much as humans emitted up to the year 2000.

And while there's a lot of uncertainty around the exact number, we know permafrost can emit a lot of greenhouse gas.

It's yet another reason why it's so important for us humans to reduce our carbon emissions as soon as possible and prevent these feedback loops.

So now you know what permafrost is and what it isn't, which is good, since it's going to play a pretty big role in our planet's future, and research suggests we should do what we can to preserve it.

With any luck, this Arctic oddity will be around long enough to be misunderstood by generations to come.

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