Arctic Sinkholes I Full Documentary I NOVA I PBS

It's not as cold as it used to be. As Brower discovered. BROWER: I checked the meat and told my brothers, "We have to get that meat out. It's leaking and we don't want that." I have resorted to taking an entire whale out of there and putting it in cold storage. ♪ ♪ NARRATOR: The melting of ice cellars is not the only threat that rising temperatures pose to this community. Recently, the sea ice that used to protect the coast from storms has begun to melt. BROWER: The storm surge is pretty dramatic. And it's going to wreak havoc on your coast here.

And the thing is, when you get down to it, a lot of the banks are rich in permafrost, and that undermines them. NARRATOR: The permafrost, exposed by the storms, is melting and crumbling. Now communities like Utqiagvik are trying to protect their homes. BROWER: These are all of our local efforts to stop the storm surge. This is our way of trying to save the town. NARRATOR: With a receding coast and warming ice basements, local communities are being hit twice by thawing permafrost. But the big melt is a problem that affects the entire Arctic. NATALI: Over the next decades and century, we expect that anywhere, around the world, in the Arctic, between 30% and 70% of the near-surface permafrost will be lost.

That range partly has to do with some scientific uncertainty, but largely has to do with how much warming will occur in the future. NARRATOR: Arctic communities now face the immediate effects. But scientists worry that this loss has implications for the entire planet. So why is thawing permafrost so dangerous? And what is the link with methane? (birds chirping) Back near Fox in Interior Alaska, Tom Douglas is about to do something that's only possible in a few places on Earth: hike deep into the permafrost. Fox's permafrost tunnel reveals that there is more to permafrost than frozen ground. DOUGLAS: That's a hoot.

That's from the longhorn steppe bison. And now they're extinct, but 18,000 to 40,000 years ago, you know, there were steppe bison here. Very exciting, here is a mammoth bone. You can see some kind of piece sticking out right there. It's quite big. NARRATOR: The tunnel reveals that the permafrost contains large amounts of organic matter. DOUGLAS: So these are reeds, kind of like grass. And you can see that they are green. They still have chlorophyll. They are also backwards. This block fell into a water source that then froze, probably about 20,000 years ago. ♪ ♪ NARRATOR: This ancient organic matter, like all life on our planet, contains carbon. (birds chirping) And it's part of a vital Earth system called the carbon cycle. ♪ ♪ As they grow, plants absorb carbon dioxide.

When they die, they or the animals that have eaten them decompose, releasing some of this carbon into the atmosphere. But in the frigid Arctic, decomposition occurs slowly. Thus, over millennia, an enormous amount of organic matter became permafrost before it could decompose, and its carbon was frozen in time. DOUGLAS: From the late 1990s to the early 2000s, people started looking at carbon stocks in permafrost. And it is a lot, about 1,400 billion metric tons. It is almost twice as much carbon as is currently in the Earth's atmosphere. When we walked in, we noticed that smell, right? You're smelling ancient bacteria and oxidized carbon.

It's almost like, well, I've heard anything from French cheese to free-range cheese, but it's an organic, almost late fall smell of wet leaves. You're smelling the oxidation of permafrost carbon. So, the big question is: that carbon that we smell, that is all over the tunnel walls, what is its final destination? And there are many people working on it. NARRATOR: In other words, how much of this carbon will end up in the atmosphere? And most importantly, at what speed? ♪ ♪ Falmouth, Massachusetts. 3,000 miles from the ice tunnel. Arctic ecologist Susan Natali investigates samples of permafrost to find out what happens when it melts.

NATALI: These are permafrost cores that were collected in different places in Alaska. Some of them are really dark, like this one in particular. And that dark color means it has a lot of carbon. ♪ ♪ NARRATOR: As permafrost warms, its carbon melts. And the carbon cycle begins once again. So the carbon becomes available for microbes to break down. And they use it as energy and break it down. And in that process, they release carbon dioxide or methane. ♪ ♪ NARRATOR: Carbon dioxide and methane are greenhouse gases. As the Earth's surface absorbs energy from the sun, it radiates some of it as heat.

In the atmosphere, greenhouse gases absorb this heat, radiating some of their energy back to Earth and warming our planet. NATALI: Greenhouse gases are a concern because they trap heat. They are useful to us because they make this planet habitable, but because there is too much atmosphere in the atmosphere, they are now making it an uninhabitable or less habitable planet. ♪ ♪ NARRATOR: It is estimated that in the mid-18th century, there were more than 2,000 gigatons of naturally occurring carbon-based greenhouse gases in the atmosphere. With industrialization, man-made greenhouse gas emissions began to increase this amount. By 2019, the total was estimated to have risen to more than 3,000 gigatons.

Over the past century and a half, Earth's average temperature has risen about two degrees Fahrenheit. ♪ ♪ Scientists agree that human emissions caused this warming. But recently, they are concerned that greenhouse gases released by permafrost may also be raising temperatures. As the name suggests, permafrost is permanently frozen ground. So we thought, "Okay, this carbon is very stable, so nothing's going to happen." But as permafrost begins to melt, this carbon becomes vulnerable. NARRATOR: Since the mid-1970s, carbon dioxide emissions from the northern Alaska wilderness have skyrocketed by more than 70%. But while we know a lot about carbon dioxide, the impact of another greenhouse gas escaping from permafrost is less known: the same one escaping from Lake Yamal and Esieh, methane.

Methane is really important because it is much more powerful in terms of its ability to trap heat. Therefore, it is about 30 times more powerful than carbon dioxide. ♪ ♪ NARRATOR: Fortunately, while carbon dioxide lasts centuries or more in our atmosphere, methane only lasts about 12 years. But as a much more potent greenhouse gas, any large-scale increase in methane emissions seriously worries climate scientists. ♪ ♪ For now, more than half of methane emissions come from human sources such as fossil fuels and agriculture, sources well understood by climate experts. But scientists are increasingly concerned about methane emissions from permafrost. It is not yet known how much methane is released from permafrost.

And that is a big problem. To control our temperature, we have a certain amount of carbon that humans can release: that is our carbon budget. NARRATOR: In 2015, the international Paris Agreement set a goal to limit global warming. Their goal was to keep the temperature rise well below two degrees, preferably 1.5 degrees Celsius. To have a good chance of staying below the 1.5 degree mark, it is estimated that humans could release a maximum of around 460 gigatonnes more of carbon dioxide. But recent climate calculations are based on computer models with incomplete information. LEE: Unfortunately, many of these Earth system models that contribute to such goals do not take into account CO2 and methane emissions from permafrost.

NARRATOR: More recent carbon budgets have begun to include permafrost carbon. But some scientists believe they still underestimate how much carbon the warming Arctic will release, making it harder to meet temperature targets and putting more pressure on societies to sharply reduce their emissions to compensate. NATALI: So we think we have a certain amount of greenhouse gases that humans can release, but our goal is wrong right now, because we're not accounting for potential methane and carbon dioxide emissions from permafrost. NARRATOR: Understanding the dynamics of thawing permafrost is now critical to predicting our climate future. So how much methane does permafrost emit each year?

And is that annual amount going to increase? (dogs barking) HANKE: Good dogs! Straight ahead, following, following, following. NARRATOR: Fairbanks, Interior Alaska. Environmentalist Katey Walter Anthony enters the frozen terrain. HANKE: Ha! Haw! Come on, Biggy, come on. (dogs whining) NARRATOR: Walter Anthony was one of the first to study Lake Esieh. He has found worrying evidence that it is not the only lake in the permafrost region that is releasing methane. ♪ ♪ WALTER ANTHONY: So when you harpoon the place, if I hear gas coming out, I'll try to light it. And if there's fire, we both have to get out of the way.

Well. Ready? Yeah. Wow... (flames roaring) That got me. Oh shoot. I'm on fire? No... I was wondering. (Both laugh) What are you smoking? (laughing) Are you okay? (laughing): Yes, I'm fine. (laughs) That was a good one. That was a good one. Alright. NARRATOR: Methane comes from permafrost organic matter that melts and decomposes at the bottom of the lake, then rises in methane bubbles to the surface. Across the Arctic, thawing permafrost is generating a host of new lakes. As the ground warms, the ice beneath the surface melts, causing the ground to sink and fill with water. And once a lake forms, you can't stop it, because the water has heat and causes the ground to thaw very quickly.

NARRATOR: The lakes then begin to release methane. WALTER ANTHONY: As methane escapes, it causes more permafrost to melt and more methane to be generated, which causes more warming, and you get what's called a positive feedback loop. NARRATOR: Positive feedback loops from permafrost regions are another scenario that is not sufficiently accounted for in current climate models. READ: As permafrost melts, greenhouse gases such as CO2 and methane will be released into the atmosphere much faster. Warming is causing more warming. NARRATOR: Because of positive feedback, permafrost emissions could increase the rate of warming, compounding the need for humans to reduce their emissions if climate goals are to be met.

But permafrost carbon is not the only potential driver of a positive feedback loop. In reality, permafrost is not the largest carbon reserve on Earth. There is a much larger reserve of carbon in the Earth's crust in the form of fossil carbon. But we don't often talk about this carbon. This is because this carbon is considered very stable. NARRATOR: But some scientists now wonder if this megacarbon source is as stable as they thought. Disturbing evidence comes from bubbles in Lake Esieh. The methane released by thawing permafrost has a particular chemical signature. When scientists at Lake Esieh studied the methane in the bubbles, they discovered that it originated deep inside the Earth.

Much deeper. ♪ ♪ Miles beneath the permafrost, deep in the Earth's crust, lie enormous reserves of fossil methane. While permafrost methane comes from thousands of years old organic matter, fossil methane comes from organisms that decayed millions of years ago. But if it is kilometers deep, how does this methane manage to penetrate the Earth's crust? And why here? On the surface, the landscape itself gives scientists a clue. SULLIVAN: By looking at the peaks around here and studying the local geology, we know that this is a very fractured and faulted region. NARRATOR: As of 2021, Alaska is the most seismically active state in the US.

In the territory near Lake Esieh, scientists have discovered a network of geological faults. Although it is not on a tectonic plate boundary, movements in the Earth's crust have caused it to crack here. The closest fault discovered so far is less than five miles from the lake. Faults create cracks in the Earth's crust through which fossil methane can rise to the surface. Although it has not been confirmed, scientists suspect that there is a fault near or directly below Lake Esieh. But if so, there is a mystery. Seismic evidence from the area suggests that Lake Esieh sits atop 500 feet of still-frozen permafrost.

This should form a rock-solid icy barrier that would trap the fossil methane inside the Earth. So how are these coming to the surface?deep reserves of greenhouse gases? So far, the team's sonar scan has revealed a 50-foot hole in the bottom of the lake. But what if you could look deeper, into the permafrost itself? Geophysicist Nick Hasson joins the team, using technology used by the military. 75 just after the bush. HASSON: I'm basically scanning the permafrost using a geophysical method called Very Low Frequency. NARRATOR: Very low frequency, or VLF, measures a special type of electromagnetic wave as it moves through the Earth.

The Navy sends these waves around the world to communicate with submarines. But as those waves pass through the Earth, Hasson's team can capture them. By measuring the speed the wave travels, Hasson can tell whether the ground beneath him is frozen or not. When moving through the ground, if there is permafrost or ice, these waves encounter a lot of resistance. But if there is no permafrost or ice, it quickly moves. NARRATOR: If strong enough, the VLF electromagnetic waves should allow Hasson to see what's beneath the lake. And then we can scan the Earth similar to how a doctor scans you with an MRI.

NARRATOR: Lake Esieh is the largest terrestrial methane leak yet found in the Arctic, but no one has used VLF to look beneath it. Until now. HASSON: Wow. Fantastic signs. Yes, I'm starting to notice a change. Well, we're past the biggest leak and there's some sort of huge anomaly going on right here where I'm located. And the VLF is getting it. It's very exciting. The signs are simply exceptional. ♪ ♪ NARRATOR: Back at camp, Hasson takes his first high-resolution look beneath Lake Esieh. This 500-foot cut of terrain beneath the lake reveals an anomaly. So the dark blue is the permafrost region.

So anything that is light blue to red is thawed. And then this shouldn't be here. There should be permafrost covering this entire area. But for some reason, what you can see here is a melting chimney that runs from somewhere below 150 meters to the surface, where we see the rising bubbles. And this is really unique. NARRATOR: So far, scientists have only seen 50 feet below the lake. Now, Hasson's VLF image allows them to look ten times deeper. Beneath the lake lies a deep layer of permafrost. But scientists now know that this hasn't simply thawed on the surface. Instead, a chimney of material has thawed through frozen permafrost: a warmer, semi-permeable passageway through which fossil methane rises to the surface.

Therefore, thawing permafrost means not one, but two sources of methane for our atmosphere. As it warms, permafrost releases its own methane gas. And as melt chimneys form inside them, they provide an escape route for fossil methane that has been safely trapped for millions of years. Scientists estimate that there are about 1.3 trillion tons of methane stored beneath the Arctic. That's almost 250 times more methane than is in Earth's atmosphere today. So, is the Esieh Lake melting chimney unique? Or is the fossil methane escaping elsewhere? While the leak at Lake Esieh is unusually large, smaller leaks of fossil methane are being discovered across the Arctic.

More than 70 sites have been found in Alaska alone. ♪ ♪ There are no current signs that the entire fossil methane reserve is moving to the surface. But the appearance of even small amounts of this ancient greenhouse gas worries some scientists. WALTER ANTHONY: If permafrost thaws, then it's a scary wild card in the climate change story, because we think there's an enormous amount of methane and natural gas trapped within the permafrost and beneath the permafrost. So, if the permafrost becomes like Swiss cheese, with a lot of holes, then you can have chimneys where that gas comes out. And that is not included in the climate models. ♪ ♪ NARRATOR: If only a small fraction of fossil reservoirs reached the atmosphere, warming could intensify, putting even more pressure on human emissions targets.

We don't know how quickly that will happen and how much methane will come out. NARRATOR: Scientists currently do not understand how quickly such a cycle could occur, or what it would look like. But there is one place on Earth that offers a chilling example of how a man-made permafrost feedback loop really works. Northeastern Siberia is home to the Chersky Mountains. In the 1960s, in a place called Batagaika, a stretch of forest was cleared to make a road. Stripped of its tree cover, the permafrost was exposed to the warm sun. As it thawed, the ground sank, toppling trees at its edges and exposing more permafrost—a positive feedback loop. ♪ ♪ Today, the strip of clear-cut forest is a depression nearly 300 feet deep and more than half a mile wide.

And it is growing. Scientists call it a mega depression. LEIBMAN: Batagaika, it is very large, but this size is due to the initial human impact. And this one is already more than a kilometer long and grows every summer. NARRATOR: Batagaika reveals how a small human impact can start a devastating feedback loop in permafrost. (birds chirping) Scientists are now trying to figure out what a feedback loop could mean for the entire permafrost region and whether it could reach a point where it becomes irreversible. This phenomenon is called inflection point. SULLIVAN: A turning point is the proverbial straw that broke the camel's back.

You can get away with adding straw for so long and then you won't be able to. And the turning point is the point of no return. ♪ ♪ NARRATOR: It's a controversial idea among climate scientists. But the possibility of a tipping point has been raised for several global climate systems, including Arctic sea ice and deforestation in the Amazon. So far, there is no conclusive evidence that a tipping point for permafrost is approaching. However, some scientists believe that some aspects of the melt are now irreversible. (soil silencing) Vladimir Romanovsky has spent decades studying permafrost change. Near Utqiagvik in northern Alaska, he investigates what happens when large wedges of ice in the ground begin to melt.

ROMANOVSKY: Before it was a more or less flat area, but then the ice melts and the surface sinks. NARRATOR: Romanovsky believes the lakes formed by melting permafrost ice have passed a point of no return. ROMANOVSKY: It took tens of thousands of years to put this ice on the ground. Now it's melting. To return all this ice to the earth will take several tens of thousands of years. So for humans, that is a definitely irreversible process. It is a turning point. NARRATOR: While melting ice forms lakes in the desert, just a few miles away, it is causing very different problems for the local community.

On the roads outside Utqiagvik, the effects of rising Arctic temperatures are easy to see. NELSON: Just from observation, when I grew up here and came here since I was a kid, the roads were a lot higher than they are now. It is literally sinking. Your bumper could get wet. NARRATOR: Lars Nelson, Alaska Native, Inupiaq, is an infrastructure consultant. He knows firsthand what thawing permafrost is doing to his community. NELSON: This road is for subsistence use; We come here and organize our hunts. It's a big part of our history and it's important that we can access it in the event of an emergency.

NARRATOR: And it's not just the roads that are sinking. In the center of Utqiagvik, Nelson meets Inupiaq Anthony Edwardsen. These are also declining. Yes. NARRATOR: He is an expert on the Inupiaq community with four decades of experience in the construction industry. Yeah, he look... this one is really fucked up. Look how it's just... EDWARDSEN: That's where the houses are sinking. NARRATOR: Local houses are built on wooden stilts. If they were built above ground, the heat used to heat the houses would thaw the permafrost below. But now the permafrost is melting on its own and the piles are starting to sink.

EDWARDSEN: When the pile is a very small base, it does not support its structure. Communities need to level the houses, move the houses, the houses need to be torn down. We are in the middle of a real estate crisis. NARRATOR: Nelson believes strategic construction is the answer. We're in it right now and we're refining it right now. We can build beautiful, good and healthy homes. We just have to pay attention to our foundation, pay more attention to the tundra we are building on. Because it's an amazing place, you know? It's the top of the world. ♪ ♪ NARRATOR: But as permafrost continues to melt, others in Alaska are looking for more drastic solutions.

GRIFFIN HAGLE: This is our portable, adjustable, sled-based house. It's on a giant steel sled, as opposed to stilts. NARRATOR: C.E.O. Griffin Hagle of the regional housing authority has a more radical plan to sink homes. HAGLE: What we would do if necessary, to move this, is connect our tow chains to these two tie-down points. We have one on this side and one on that corner of the building over there. Attach it to a piece of heavy equipment, Caterpillar, and then drop it off the pads and basically tow it through the snow in the winter. ♪ ♪ NARRATOR: As temperatures rise, Hagle looks for ways to protect some of the most isolated communities in the United States.

HAGLE: I think this is the largest municipality in the world, by area. We offer affordable housing in eight villages in an area the size of Minnesota, just without roads. NARRATOR: No houses have been removed from Alaska yet. But the warming Arctic has forced some cities to relocate. And Hagle believes houses will soon start moving. And there are several communities, especially in rural Alaska, Native communities, that are increasingly at risk of relocation due to global warming. And this gives us the advantage of having the option, the adaptability, to move that structure if necessary. The native peoples, the indigenous communities that have called this place home for thousands of years, have come up with all kinds of in

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tions to make life work here.

So we draw a lot of inspiration from that and see it as kind of a continuation of a long, long tradition of in

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tion. ♪ ♪ NARRATOR: As Arctic residents adapt to their changing world, scientists are striving to build a better picture of our climate future. The methane craters are just one sign of a region that is experiencing unprecedented changes... ...that put communities with deep ties to this land at risk. BROWER: We've been whaling here for more than 4,000 years. (birds squawking) We have adapted again and again. Today, we may not be able to do it alone. NARRATOR: But the great thaw is not just a regional problem.

What is happening in the Arctic could really affect everyone on Earth. NARRATOR: Greenhouse gases from the Arctic will intensify global warming in the future. It is difficult to predict how quickly. And positive feedback loops could accelerate beyond human control, making our decisions today even more urgent. LEE: Because it is very difficult to take control of natural systems, it is even more important for us to reduce our emissions. NATALI: These craters are a really important and worrying indicator that things are changing and that the Arctic is melting and the Arctic is melting. And the future of the Arctic is a very different place than it was several decades ago. ♪ ♪ ♪ ♪ ANNOUNCER: Episodes of "NOVA" are available with Passport.

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