It was just a year ago that Sophie Opfergelt and her UCLouvain Earth and Life Institute team were taking permafrost samples in Alaska. Today, she is already drawing conclusions from analysing them but is not yet sure about the impact of melting Arctic permafrost on our planet’s future.
When spring beings, nature awakens everywhere. In the Arctic, too, ice has melted. Last year, in May 2018, Sophie Opfergelt, a geologist and professor at UCLouvain's Earth and Life Institute, and her team observed permafrost thaw with their own eyes. Permafrost is ground that has been frozen for two or more consecutive years in Arctic regions. Due to global warming, this normally permanently frozen layer now thaws.
An ecosystem in full transformation
Prof. Opfergelt and her team ventured into the field last year because the scientific community's overall conclusion is clear: in the Arctic, under the influence of global warming, environments are being degraded. And the degradation is widespread. First, as the temperature increases, so does the temperature of permafrost. In some places it even tops 0° C, thus melting ice that had never melted. Second, these temperature changes cause subsidence of the earth's surface: today, 30% of the Arctic is at risk of collapse due to thawing. Finally, all these changes have an impact on vegetation. In high latitudes, the majority of vegetation is of the tundra type – it’s impossible for a tree to take root. But further south, where the permafrost is deeper, the environment is called taiga (similar to a boreal forest). On a map, the distinction between these two types of vegetation is very clear. Scientists have estimated that over the past 30 years taiga vegetation has been displaced five degrees of latitude to the north. As such degradation is being increased by polar amplification, we’re witnessing the spectacular modification of an entire ecosystem.
What do minerals have to do with it?
Within this wider observation, Prof. Opfergelt decided to study the influence of this degradation on mineral nutrients, which has thus far not been studied. Indeed, in the thawing soils, there are certainly organic nutrients that many scientists study because they produce the greenhouse gases CO2 and methane (CH4). But there are also mineral nutrients that, when released by thawing, are able to interact with organic carbon. As soon as the soil thaws, these minerals come into contact with water and release nutrients, making them available to microorganisms that degrade organic matter and vegetation. Since the beginning of the project, 18 months ago, Prof. Opfergelt's team has been trying to provide an overall assessment of the effect of permafrost thaw in the Arctic regions on the mineral constituents of soils. This assessment will improve climate model predictions by clarifying the role of mineral alteration in modulating the role of carbon in climate change.
Two scenarios for the planet’s future
This research is important owing to two (opposing) scenarios concerning carbon decomposition and its return to the atmosphere. In one scenario, defrosted minerals provide a source of nutrients to microorganisms responsible for carbon decomposition, increasing greenhouse gas emissions. In the other, more positive scenario, the mineral surfaces exposed by thawing could themselves trap carbon and make it less accessible to microorganisms; greenhouse gas emissions are thus reduced as the amount of carbon is reduced. It remains for scientists to quantify permafrost reserves of mineral nutrients to see whether they are released and, if so, what happens.
New research avenues
Prof. Opfergelt’s project is called WeThaw and is being funded over five years (2017-22) by the European Research Council (ERC). In May 2018, the mission was to bring back samples of water, rock, soil and vegetation. Today, 18 months in, the team is posing new questions:
- What are the mineral nutrient reserves in soils that are still frozen but thawing?
- Are these reserves available and soluble?
- Does vegetation benefit from these minerals?
To answer these questions, Prof. Opfergelt carries out studies on several scales. First, there is a local and seasonal field study in Alaska. In the thaw season, how are studied elements (rock, soil, water, vegetation) transferred? Then, in order to analyse the ecosystem’s evolution, the team collects data on samples from an experimental site that has been affected by natural degradation of permafrost for 30 years, to compare them to data it collects on a site subjected artificially to warming for 10 years. Finally, on a more global scale, she has access to samples collected at various sites across the Arctic, thanks to a series of collaborators in various countries. The goal is, in the long term, to progressively build a database of mineral content in the Arctic permafrost.
Prof. Opfergelt has already drawn some conclusions: ‘The first results seem to indicate that the permafrost is richer in mineral elements than the upper part, in terms of quantity. There is a non-negligible and larger stock of mineral nutrients.’ Some areas remain unknown, however: it’s not yet possible to predict whether these mineral elements will be released, and their influence on the fate of organic carbon is not yet known.
Field work and analysis
In the coming months, the project will return to the field. The team will return to Alaska in August to collect samples and compare them with those of the initial thaw. The goal is to understand what happens when the system changes, and when the ground is at its maximum thaw. In addition, from an analytical point of view, the team is working on the development of geochemical tools to track processes during the thaw, especially when the permafrost is in contact with water. Prof. Opfergelt hopes to understand if and how mineral elements are released. By providing these new data, UCLouvain will improve models on these regions to predict how their ecosystems will evolve in the coming years and decades.
A glance at Sophie Opfergelt's bio
Having earned her master’s degree in geological sciences at UCLouvain, Sophie Opfergelt completed her PhD in agricultural sciences and biological engineering at UCLouvain on the development of geochemical tracers of the silicon cycle in the soil-plant system. She then completed a postdoctorate in the Earth Science Department of the University of Oxford before becoming an FNRS research fellow at UCLouvain's Earth and Life Institute. At that time, she worked on the development of isotope tools for understanding the origin of the flow of mineral elements exported from soil to rivers. In 2014, she received the Ebelman Award from the International Association of Geochemistry. The same year, she became an FNRS research associate at the UCLouvain Earth and Life Institute. Since 2017, she has led the WeThaw project, funded by the European Research Council (ERC).