Katey Walter Anthony has studied some 300 lakes across the tundras of the Arctic. But sitting on the mucky shore of her latest discovery, the Arctic expert said she’d never seen a lake like this one.
Set against the austere peaks of the Western Brooks Range, the lake, about 20 football fields in size, looked as if it were boiling. Its waters hissed, bubbled and popped as a powerful greenhouse gas escaped from the lake bed. Some bubbles grew as big as grapefruits, visibly lifting the water’s surface several inches and carrying up bits of mud from below.
This was methane. As the permafrost thaws across the fast-warming Arctic, it releases carbon dioxide, the top planet-warming greenhouse gas, from the soil into the air. Sometimes, that thaw spurs the growth of lakes in the soft, sunken ground, and these deep-thawing bodies of water tend to unleash the harder-hitting methane gas. But not this much of it. This lake, which Walter Anthony dubbed Esieh Lake, looked different. And the volume of gas wafting from it could deliver the climate system another blow if lakes like this turn out to be widespread. The first time Walter Anthony saw Esieh Lake, she was afraid it might explode — and she is no stranger to the danger, or the theatrics, of methane. In 2010, the University of Alaska at Fairbanks posted a video of the media-savvy ecologist standing on the frozen surface of an Arctic lake, then lighting a methane stream on fire to create a tower of flame as tall as she is. It got nearly half a million views on YouTube. So now, in the Arctic’s August warmth, she had come back to this isolated spot with a small research team, along with her husband and two young sons, to see what secrets Esieh Lake might yield. Was it simply a bizarre anomaly? Or was it a sign that the thawing Arctic had begun to release an ancient source of methane that could worsen climate change? One thing she was sure of: If the warming Arctic releases more planet-warming methane, that could lead to. . . more warming. Scientists call this a feedback loop. “These lakes speed up permafrost thaw,” Walter Anthony said. “It’s an acceleration.” There was only so much the team would learn from the instruments they had hauled here. To get a firsthand look, they would have to get in. They’d brought their wet suits.ARCTIC LAKES THAT DON’T FREEZE
Walter Anthony, who grew up close to Lake Tahoe, was captivated by Arctic lakes at 19, when she spent a summer at Siberia’s picturesque Lake Baikal.
“I love the solitude of remote lakes and the mystery of what lies beneath the water surface.” Two decades and several academic degrees later, she was asked by a Native Alaskan group, the NANA Regional Corporation, to search for methane seeps in northwest Alaska, since the gas, despite its climate downsides, could provide a fuel source for remote communities. How do you find a lake in Alaska that leaks methane? Well, there’s one telltale sign: They don’t fully freeze over. In April 2017, Walter Anthony put out word among residents of Kotzebue, Alaska, that she was looking for weird lakes. An email that month from a pilot led her to the Noatak region, not far above the Arctic Circle. Last September, she made her first visit to the lake — set against sloping hills covered with rust-colored mosses and blueberry bushes. She brought her family and a graduate student to the spot, so remote it required several days of camping and was completely off the grid. At first, the sheer volume of gases at Esieh Lake was slightly terrifying, but as Walter Anthony grew accustomed to the lake’s constant spluttering, her fear gave way to wonder.‘HOTSPOT’
For the second trip, Walter Anthony had brought a larger team of researchers, more equipment and her family — her husband, Peter Anthony, and sons, Jorgen, 6, and Anders, 3.
The team brought instruments for sampling gases, four inflatable boats, large crates of food, eight tents, a satellite phone for emergencies and two shotguns. As with much of the Alaskan wilderness, the lake is frequented by grizzly bears, and the bear scat around the camp kept everyone keenly aware of their surroundings. A week before the trip, Walter Anthony had published a major study delivering worrisome news about Arctic lakes in general. Her husband, Peter — also a scientist at the University of Alaska at Fairbanks – was a co-author. The research tackled the central question now animating scientists who study permafrost soils, which can reach depths of nearly 5,000 feet and were laid down over tens of thousands of years or more as generations of plants died and sank beneath the surface. Because of the cold, those carbon-rich remains never fully decomposed, and the soil preserves them in an icy purgatory. Now, though, as the Arctic warms, decomposition is starting up — and it gives off greenhouse gases. Scientists know the permafrost contains an enormous amount of carbon — enough to catastrophically warm the planet if it were all released into the atmosphere. But they don’t know how fast it can come out and whether changes will be gradual or rapid. That’s where Walter Anthony’s work came in. The authors examined the prevalence of thermokarst lakes, which form when the wedges of ice within permafrost melt and create voids that then fill with water. And they found that the continuing growth of these lakes — many of which have already formed in the tundra — could more than double the greenhouse gas emissions coming from the Arctic’s soils by 2100. That’s despite the fact that the lakes would cover less than 6 percent of the total Arctic land surface.ALASKA
Fewer
More emissions
Study area
Barrow
Rate
15
10
5
0
5
10
15
No data
metric tons of carbon dioxide-equivalent emissions per year
Anchorage
Esieh Lake
Kotzebue
Fairbanks
Nome
100 MI
Note: Data aggregated over hexagons 11.1 square miles in size.
Abruptly thawing thermokarst lakes may add significant carbon emissions by the end of the century
1.5 billion metric tons carbon dioxide-equivalent per year
Emissions caused by
gradual thaw from land
1
Germany’s total carbon emissions in 2016
0.5
Emissions caused by
abrupt thaw from lakes
0
1999
2025
2050
2075
2101
‘IT’S KIND OF FREAKY’
If it weren’t for the bubbles, the large patches of silty water they create and the slightly unsettling fact that you could light the emerging gases on fire (at one point, Walter Anthony did just that), Esieh Lake might be an idyllic scene. But these features, combined with the fact that it appears to be frequented by grizzly bears, render it more alien than bucolic.
An entirely new lake has formed near Fairbanks, Alaska, and has kept growing since 1949.
Fairbanks
AUGUST 1996
200 FT
AUGUST 2018
Approximate
lake surface
area in 1996
Source: Satellite imagery via DigitalGlobe
A TROUBLING HYBRID
After four nights of camping, the team packed up to make the two-hour boat trip to Kotzebue, Alaska, the first leg on the journey home. Walter Anthony wouldn’t have all the new data processed for a while, but she did have a pretty good hypothesis about what is happening at Esieh Lake.
Permafrost contains a lot of carbon — but in some locations, permafrost soil, and its characteristic wedges of embedded ice, also sits atop ancient reserves of fossil fuels, including methane gas. So as the Arctic warms — which it is doing twice as fast as the rest of Earth — these gases could be liberated into the atmosphere. The holes in the bottom of Esieh Lake could therefore be an underwater cousin of odd craters that have appeared in the Siberian tundra in recent years, suspected to have been caused by underground gas explosions. If this is right, then Esieh Lake becomes a kind of hybrid — and a worrying one. It’s not a pure thermokarst lake, though some thermokarst appears to be forming around the lake’s expanding edges, tipping shoreline trees as the ice in the permafrost melts and the ground destabilizes. But the thawing of permafrost at the lake bed might also have unleashed older fossil gases from a reserve that had been sealed — creating another kind of worrisome lake. “This is an additional source,” Walter Anthony said.This story has been updated to clarify the different impacts of carbon dioxide and methane gas.
Yorumlarınızı Bizimle Paylaşın
Sadece üyelerimiz yorum yapabilir, hemen ücretsiz üye olmak için Tıklayın