Digging deeper into the permafrost-carbon feedback The earth’s permafrost is thawing at an unprecedented rate, leading to the exposure of previously inert soil organic carbon, which may then be released into the atmosphere as either carbon dioxide or methane. The WeThaw project aims to build a deeper picture of how permafrost responds to thawing, which will also help improve climate models, as Professor Sophie Opfergelt explains. The rate at which permafrost has thawed over the last 30 years or so is unprecedented in the geological history of the earth. As more and more previously inert soil organic carbon is exposed to microbial decomposition, it is being released into the atmosphere as either carbon dioxide (CO2) or methane. “As deeper parts of the permafrost thaw every year more and more of the carbon becomes dynamically active, rather than inert,” explains Sophie Opfergelt, Professor of Geochemistry at UCLouvain. This thawing leads to increased release of carbon, which in turn causes temperatures to rise, creating a feedback loop which intensifies over time. “There is an enhancement of the process each time, it is called the permafrost-carbon feedback,” says Professor Opfergelt. WeThaw project A lot of attention is currently focused on the extent of this thawing and on quantifying the amount of carbon that is emitted into the atmosphere. As leader of the WeThaw project, Professor Opfergelt is looking more at other mineral constituents in the soil, which she believes also play a role in the permafrostcarbon feedback. “Our hypothesis is that the exposure of these other constituents will affect the fate of organic carbon upon thawing,” she
Permafrost Thaw Organic Carbon
Organic Carbon
Minerals
Minerals
With permafrost thaw, previously frozen organic carbon is exposed. The project WeThaw investigates the influence of permafrost mineral constituents on the fate of soil organic carbon upon thawing.
the permafrost. “We travelled there at the transition between Winter and Spring, when the ground is frozen to the top. We also went at the very end of Summer, when the surface of the soil is unfrozen, so the soil has thawed to its greatest extent,” continues Professor Opfergelt. At the end of Summer Professor Opfergelt and her colleagues are able to capture the maximum thaw depth. “Below this level the soil is still frozen. This permafrost has not thawed, for at least 10,000 years,” she says.
As deeper parts of the permafrost thaw every year more and more of the carbon becomes dynamically active, rather than inert. outlines. A certain proportion of carbon in the soil will become free upon thawing, while a certain proportion will bind to minerals, a topic central to the project’s work. “We aim to quantify the balance between the proportion of carbon that will become free upon thawing and the proportion of carbon that will bind with minerals,” says Professor Opfergelt. This research holds important implications, as it will help scientists assess how much free carbon is released into the atmosphere, which can then contribute to the permafrost-carbon feedback. Researchers in the project have been working at a field site in Alaska, aiming to gain deeper insights into the thawing of
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The wider context here is ongoing concern about the impact of climate change and its likely trajectory in future. Interactions in the permafrost are not accurately represented in the climate models currently used by the IPCC, believes Professor Opfergelt, who hopes the project will make an important contribution in this respect. “By collecting more data, we will help to parameterise the next generation of climate models, to more precisely forecast the evolution of the climate system,” she outlines. While the project’s work is based on data from Alaska, collaborations have been established with other institutions pursuing similar work in other areas, from
which researchers can then look at the global picture. “We also want to go to a larger scale, and to identify how this mineral weathering would affect Arctic regions on the global level,” says Professor Opfergelt.
WeThaw Mineral Weathering in Thawing Permafrost: Causes and Consequences Professor Sophie Opfergelt UCLouvain, Earth & Life Institute Croix du Sud 1, L7.05.10 1348 Louvain-la-Neuve Belgium T: +32 10 47 36 42 E: sophie.opfergelt@uclouvain.be W: https://sites.uclouvain.be/wethaw/
Professor Sophie Opfergelt is a FNRS Research Associate in geosciences at UCLouvain. Her research is devoted to Arctic soils facing changes. Her focus is on the response of internal permafrost processes upon thawing.
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