Willow Lake and River are filling in with sediment as thawing permafrost leads to landslides in the Mackenzie Delta — dramatically increasing the amount of organic material in rivers and lakes.
Located just at the edge of the Delta near Aklavik, the Willow River basin has been feeling the effects of climate change for over 30 years. Research facilitated through the Aurora Research Institute (ARI) and assisted with traditional knowledge scientists has found that 40 per cent of the 800-square-kilometre river basin has been affected by permafrost landslides, and they’re becoming more common.
“The frequency of these events have led to an like increased amount of sediment resulting in the rerouting of the river,” said Jaedyn Smith, who was speaking Sept. 23 as part of the ARI’s Virtual Speaker Series with fellow University of Alberta (U of A) researchers Suzanne Tank and Marina Taskovic, detailing their work in the Mackenzie Delta, particularly the Peel Plateau.
“Recent work has shown that the changes associated with permafrost thaw can persist for decades after the initial disturbance, so understanding how these changes have played out over time in the past will hopefully help us be able to predict how things will continue to change in the future.”
Using core, water and snow samples collected over the year, Smith is working to determine how quickly the infill of the lakes happened. She also is looking at what happens to sediments locked away in the permafrost, both organic and inorganic, and how they interact with the surround ecosystem after being freed from their frozen banks.
Melting permafrost is a serious problem in the fight against climate change, not only because of the methane and carbon dioxide gas released as it thaws, but also the enormous variety of material frozen in the soil entering water bodies and mixing with current ecosystems.
“Aquatic ecosystems, by their very nature, integrate landscapes,” said Tank. “They really integrate change. These aquatic systems are critically affected by changes on land, so if you impose agriculture or you impose logging you’re going to fundamentally change the signature of stream water.
“A kind of flip on that you can use your streamlined stream water to understand that change. If you’re measuring change that’s happening over a broad enough landscape these some of the processes that happen in water can feed back into larger regional and global processes.”
‘Thousandfold’ increase
Tank said her team found a hundred-to-thousandfold increase in carbon downstream of permafrost slumps in the Mackenzie Delta. However, as much or even more carbon is being deposited on shorelines along the river systems, called a debris tongue, where she estimated it should sit for a very long time if left undisturbed.
However, the carbon released by slumping has the potential to fundamentally change ecosystems, explained Taskovic, particularly to the food web. Using samples of water, slime and soil, she was able to measure the biodiversity and health of microbes and tiny organisms called phytoplankton and zooplankton.
A significant increase in nutrients in the water could have dramatic effects on the ecosystem, providing more nutrients for some organisms which could push out other organisms.
“Through this slumping activity we have this huge movement of often significant quantities of sediment over the land,” she said. “These sediments contain both inorganic and organic matter, nutrients, ions and other chemical constituents.
“As these head walls erode and all these sediments move they eventually enter streams where they can drastically modify the physical and chemical environment.”
Taskovic also was able to measure the amount of nutrients used by the population, though she noted she needed to conduct more lab experiments to draw conclusions on what is happening below the surface.
How soil runoff affects downstream ecosystems is of particular interest in the North, which is warming three times faster than the global average as climate change progresses. Locked away in the melting permafrost is ancient methane, carbon dioxide and biomass able to produce more of the above. Tank said while the North only contains 15 per cent of the global landmass, that landmass holds a third of all carbon contained in soil on Earth.
When permafrost melts, it releases both organic and inorganic compounds into the surrounding environment. The organic compounds typically enter the food web, either consumed by decomposing bacteria and other microbes, which produce more of the greenhouse gases carbon dioxide and methane as a byproduct.
Another source of carbon comes from the breakdown of minerals in the melting permafrost, though Tank noted the flow of carbon from the permafrost to the atmosphere wasn’t just one-way and different minerals could either release or trap carbon dioxide. However, work by her team showed the inorganic runoff also produces a burst of carbon, though the reaction is over fairly quickly.
Most of the permafrost in the Beaufort Delta was deposited by the Laurentide Ice Sheet roughly 20,000 years ago and essentially froze as soon as the ice sheets weren’t insulating them anymore. Those deposits were largely composed of inorganic material, with much of the active layer — the top part of the soil which thaws in the summer — being laid after the ice sheet began to recede some 12,000 years ago.
Noting all their research would not be possible without outside assistance, Tank thanked colleagues at the U of A, ARI, the United States Geological Survey, GNWT, ARI, Vrije Universiteit Amsterdam and the communities of Fort McPherson and Aklavik. She noted the resources and input from Tetlit and Ehdiitat Renewable Resources Councils were indispensable in their research.
All three researchers said the experience of working in the North was a life changing experience and couldn’t wait to come back for more samples.
“I’m hoping to continue to work with local land users and researchers in order to build our understanding of this area in order to hopefully increase northern community sustainability infrastructure longevity and environmental stewardship,” said Smith. “I’m really thankful for all the land users and wildlife monitors that were able to help us out on this project and I definitely learned a lot and I’m excited to keep learning more about it.”
