by Emily Fischer
Trudging through snow up to their thighs, researchers Nicholas Hasson and Phil Hanke pull 200 pounds of equipment through boreal terrain near Fairbanks, Alaska. Once they reach their destination – a frozen, collapsing lake — they drill through two feet of ice to access frigid water containing copious amounts of methane.
Hasson lies flat on his stomach and reaches both of his arms into the subzero water. The stench of 40,000-year-old rotting vegetation floats up from the permafrost. He attempts to open the valve on a piece of equipment underneath the water’s surface using his fingers, but his thick protective gloves (water would instantly freeze onto his arms, otherwise) make simple tasks challenging. Finally, he manages to collect his sample, close the valve, and put a stopper in the vial, which is now full of methane gas.
The researchers then trek back to their lab to analyze these samples as part of ongoing field research to fill in a key knowledge gap in climate science: What happens to thawing permafrost in winter?
Hasson, a student researcher with NASA’s Arctic Boreal Vulnerability Experiment, or ABoVE, has been studying Alaskan lakes for three years. His team at the University of Alaska Fairbanks researches how thawing permafrost in Arctic regions contributes to climate change.
Permafrost is ground in mainly polar regions that stays frozen throughout the year, for multiple years. Almost 25% of the Northern Hemisphere contains permafrost. Partially decayed plant matter is trapped within the permafrost, creating a sort of “dirty, dusty, carbon-rich” layer of icy soil, as Hasson described.
Permafrost, he continued in analogy, is like a giant carbon freezer that has been storing organic material for tens of thousands of years. Over the past several decades, as climate change warmed the region, it’s as if someone has left the door open and all the contents of the freezer are thawing. As permafrost thaws, trapped plant matter is broken down by microbes; as a result, carbon dioxide and methane—a greenhouse gas 25 times more potent than the former—are released into the atmosphere.
Thawing permafrost can also collapse, creating depressions that fill with rain and melting snow to form thermokarst lakes, accelerating permafrost thaw and the subsequent release of greenhouse gases.
As the methane bubbles to the surface of lakes in the winter, it freezes in the ice, forming pockets of varying sizes and shapes. These pockets create unique patterns on top of the frozen lakes. In the summer, visitors can watch little bubbles burst at the water’s surface like a hot spring, releasing methane into the atmosphere. This scene illustrates how much the environment here has changed in a region warming twice as fast as the rest of the planet. Only a few decades ago, Arctic winters were colder, many of these lakes didn’t exist and the permafrost was rock solid.
How permafrost behaves in winter has largely been a mystery, but basic physics tells us there’s a lot to learn about its behavior during those darker months. For instance, heat travels slowly through water, so the water in Alaskan lakes holds heat and thaws permafrost partway into the cold season. It’s like lying on the beach in the sun and then walking into an air-conditioned building: your skin still feels warm for a while. Scientists can’t get the whole picture on methane emissions unless they take consistent measurements year-round.
Because planes can only take airborne methane measurements in the summer when there isn’t much snow coverage and because field researchers don’t usually take mid-winter measurements, there is an eight-month gap in the data set – eight months that could completely change how scientists model methane emissions, which have nearly tripled in the past 200 years. These models are crucial in understanding methane’s role in climate change. And that’s why Hasson and his colleagues are in the middle of the Alaskan wilderness: to study methane emissions year-round and provide data for developing climate models.
Hasson and Finke’s university lab will age the gas samples they collect in the field using carbon isotopes to better understand how ancient carbon is being transported into the atmosphere. Even now, in the summertime when airborne measurements are possible, the field team still collects samples at thermokarst lakes and takes them to the lab for analysis.
Hasson said a combination of many different types of measurements and methods is vital to their success. The ABoVE team uses absorption spectrometry to measure methane emissions by shooting lasers through large chambers placed in the water. They also use an insulated sled nicknamed “the coffin” to protect their delicate equipment from the cold while traveling in the field. The team even carries around a giant magnet that can image the ground layers below them, mapping thawing regions of the permafrost. All these methods are the pieces to understanding the puzzle of Arctic permafrost.
Field researchers make observations and collect data so that others can put the pieces in computer models and see the greater picture. “I don’t actually make the predictions,” Hasson said. “I’m just gathering the evidence so that people can put the puzzle together and try to figure out what’s going to happen.”
But “just” gathering the evidence underestimates the task at hand. Even in the cold, Hasson must walk hours to each remote Alaskan lake, pulling his equipment along, following densely forested trails that are too narrow for snow machines.
To save time in a season when daylight is limited and the cold unbearable, Hasson and Hanke, an ABoVE research technician, had the idea to use Hanke’s sled dogs for field travel. The dogs are used to running through winding trails and rough terrain while pulling heavy cargo. And this way, the two researchers get a much-needed break from hauling equipment.
“What’s unique is that [dog mushing’s] original intent was to supply healthcare to remote places in Alaska,” Hasson said. “And now, a century later, we’re staying true to that philosophy and collecting long-term data to know the health of our ecosystems.”