Across the Arctic, lakes emit dangerous greenhouse gases

The first time Walter Anthony saw Esieh Lake, she was afraid it could explode – and she's no stranger to the danger, or theatricality, of methane. In 2010, the University of Alaska at Fairbanks released a video of the media ecologist standing on the frozen surface of an arctic lake and then lit a stream of methane on fire for create a flame tower as tall as her. He had almost half a million views on YouTube.

Then, in August, in the heat of the Arctic, she had returned to this isolated place with a small research team, along with her husband and two young sons, to see what secrets might give Lake Esieh. Was it just a weird anomaly? Or was it a sign that the Arctic thawing had begun to release an ancient source of methane that could worsen climate change?

One thing she was sure of: if warming the Arctic released more methane, it could lead to increased warming. Scientists call this a feedback loop.

"These lakes are accelerating the permafrost thaw," Walter Anthony said. "It's an acceleration."

There was so much that the team would learn the instruments that they had transported here. To get a firsthand glimpse, they had to enter. They had brought their suits.

Walter Anthony, who grew up near Lake Tahoe, was captivated by the Arctic lakes at age 19, while she was spending a summer at scenic Lake Baikal in Siberia.

"I love the loneliness of secluded lakes and the mystery of what lies beneath the surface of the water."

Two decades and several university degrees later, an indigenous group in Alaska, the NANA Regional Corporation, asked him to look for methane seeps in northwestern Alaska because gas, despite its climatic disadvantages.

How do you find a lake in Alaska that is leaking methane? Well, there is a telling sign: they do not freeze completely.

In April 2017, Walter Anthony revealed to residents of Kotzebue, Alaska, that she was looking for strange lakes. This month, an email sent by a pilot led to the Noatak area, not far from the Arctic Circle. Last September, she made her first visit to the lake, on sloping hills covered with rust-colored mosses and blueberries. She brought her family and a graduate student on site, so far that it took several days of camping and that she was completely out of the grid.

At first, the volume of gas at Esieh Lake was a bit terrifying, but while Walter Anthony was used to constant stuttering of the lake, his fear gave way to wonder.

Its sounding devices have captured huge holes at the bottom of the lake. Pockmarks, she calls them, "unlike anything I've ever seen in an Arctic lake."

Most of Esieh is quite shallow and averages only a little over a meter deep. But where the gas bubbles gather, the ground suddenly falls, a fall marked by the disappearance of all visible plant life.

Measurements showed that the lake plunged about 15 meters deep into one area and about 4.5 meters into another. When they first studied them, Walter Anthony and his graduate student Janelle Sharp named these two groups of seepage W1 and W2, abbreviated as "Wow 1" and "Wow 2."

The next discovery came from the laboratory. When scientists examined gas samples, they found the chemical signature of a "geological" origin. In other words, the evacuation of the lake's methane seemed to emerge not from the direct thaw of frozen arctic soil or permafrost, but rather from a much older fossil fuel reservoir.

If it happened all over the Arctic, Walter Anthony thought that if fossil fuels buried for millennia were now exposed to the atmosphere, the planet could be even more threatened.

For the second trip, Walter Anthony had brought in a larger team of researchers, more equipment and his family – his husband, Peter Anthony, and his sons, Jorgen, 6, and Anders, 3.

The team provided instruments for gas sampling, four inflatable boats, large crates of food, eight tents, a satellite phone for emergencies and two shotguns. As in most of Alaska's wilderness, the lake is frequented by grizzlies, and the presence of bears around the camp has made everyone aware of their surroundings.

A week before the trip, Walter Anthony had published a major study broadcasting disturbing news about Arctic lakes in general. Her husband – also a scientist at the University of Alaska at Fairbanks – was co-author.

The research focused on the central issue now driving scientists studying permafrost soils, which can reach depths of nearly 1.5 kilometers and have spread over tens of thousands of years. Because of the cold, these carbon-rich are never completely decomposed and the soil keeps them in an icy purgatory. Now, as the Arctic heats up, decomposition begins and releases greenhouse gases.

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Scientists know that permafrost contains a huge amount of carbon, enough to heat the planet catastrophically if released into the atmosphere. But they do not know how fast it can come out and whether the changes will be gradual or rapid.

This is where the work of Walter Anthony comes in.

The authors examined the prevalence of thermokarst lakes, which form when ice wedges in permafrost melt and create voids that then fill with water. And they found that the continued growth of these lakes – many of which have already formed in the tundra – could more than double greenhouse gas emissions from Arctic soils by 2100. total land area of ​​the Arctic.

Scientists have been intrigued by a spectacular spike in methane concentrations in the atmosphere that, since 2006, have produced an average of 25 million tonnes more per year. The study by Walter Anthony revealed that Arctic lakes could more than double that increase.

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Overall, if Walter Anthony's conclusions are correct, the total impact of melting permafrost could be similar to the addition of two major fossil fuel emitting economies – let's say two more Germany – to the planet. And that does not take into account the possibility of more lakes like Esieh, which seems to be a different phenomenon than thermokarst lakes, emitting gases faster.

The landscape surrounding Lake Esieh itself is marked by the rapid thawing of frost.

Along the coast, much of the hill had collapsed, a shift that two team members reported had occurred since May, the date of their last visit.

This "thaw crisis" was a classic example of rapid thawing of permafrost. He had left behind a wall of muddy ice and small islands of peat and moss.

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If there were no bubbles, the large expanses of loamy water that they create and the fact that you could ignite emerging gases in flames (Walter Anthony l?) done at one point), Esieh Lake could be an idyllic scene. . But these features, combined with the fact that it seems to be frequented by grizzlies, make it more alien than bucolic.

But Walter Anthony and his research technician Philip Hanke, 25, were determined to explore it from the inside. On the second day of the trip, they put on suits and snorkels and plunged into cold water, less than 15 degrees Celsius.

They wanted to see the methane infiltrate closely and learn what they could by swimming among the bubbles.

Hanke went first, venturing into the more vigorous bubble site, Wow 2. There was very little visibility. But, groped in the dark, Hanke could feel the shape of things.

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"It's a bit weird," he reported after surfacing. "Where the hole enters, it bends and flattened, and it fell, and that was where there were very loose sediments, and I could put my hands on it."

"So there are different edges, you say?" Walter Anthony asked.

"Yeah, it was a ledge."

The second site, much deeper, was less dark, more peaceful. Walter Anthony was still in awe when she came looking for air.

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"You are just watching this stream of bubbles rising directly to your face, and they are so sweet that they surround you," she said. "And the sunlight is upon them – it's like out of this world but under this world."

Another scientist, Frédéric Thalasso, had come from Mexico City and spent days measuring the gas around the lake. His first results: Esieh's emissions were very high and clearly targeted fossil fuels.

The lakes where he had experienced similar activity were in the tropics and polluted – ideal conditions for methane production, said Thalasso, a scientist at the Center for Research and Advanced Studies at the National Polytechnic Institute in Mexico City.

But these lakes have gas flows "probably 100 times lower than those of this lake," he said.

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His instruments also detected ethane, butane and propane – classic signatures of fossil origin.

Later, after processing his data, he estimated that the lake produced two tonnes of methane daily, the equivalent of the methane emissions of about 6,000 dairy cows (one of the world's largest sources of methane) . This is not enough to constitute a big climate problem, but if there are many more lakes like this – well, that's another story.

After four nights of camping, the team went to Kotzebue, Alaska, the first leg of the return trip. Walter Anthony would not have processed all the new data for a while, but she had a pretty good assumption about what's going on in Esieh Lake.

Permafrost contains a lot of carbon, but in some places, the permafrost soil and its characteristic built-in ice corners are also found over old fossil fuel reserves, including methane. As the Arctic heats up – which is twice as fast as the rest of the Earth – these gases could be released into the atmosphere.

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The holes in the bottom of Lake Esieh could therefore be an underwater cousin of some craters that have appeared in the Siberian tundra in recent years, allegedly caused by underground gas explosions.

If so, Lake Esieh becomes a kind of hybrid – and disturbing.

This is not a pure thermokarst lake, although some thermokarst seem to form around the lake's expanding edges, upsetting shore trees when the ice in the permafrost melts and the ground becomes destabilized. But the melting of permafrost at the bottom of the lake might also have released some old fossil fuels from a reserve that had been sealed, creating another type of disturbing lake.

"It's an additional source," Walter Anthony said.

Carolyn Ruppel, who heads the gas hydrates project at the US Geological Survey, said Walter Anthony's theory makes sense. Thawing permafrost could release ancient fossil fuels in the areas where they intersect.

But more research is needed to prove that this is causing widespread emissions in the Arctic, she warned.

Nobody knows how long the seeps began to bubble or what the trigger was.

From a scientific point of view, the fact that these lakes emit methane rather than carbon dioxide has a limited advantage.

Methane hits the atmosphere with force and speed, then dissipates largely after a decade or two – far from carbon dioxide, which is less powerful but persists for centuries and even millennia. While methane hampers climate change and amplifies the immediate temperature of the planet, it does not leave the same legacy in the long run.

In the meantime, some scientists say they are not yet sure about the gravity of Arctic lakes for the climate or that permafrost emissions will actually double.

"This is not the final figure," said Vladimir Romanovsky, one of Walter Anthony's colleagues at the University of Alaska at Fairbanks and a recognized permafrost expert.

At this point, it would be premature to call Esieh Lake the sign of a climate disaster. It is a strange and dramatic site, but its message remains partly veiled.

The next few years will probably reveal what lies behind Esieh and if she has many cousins ​​at the top of the world.

From here, we could also see if the great thaw of the Arctic will have thwarted attempts to stop global warming.