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The permafrost soils of the Arctic are the cold stores of the North. What they shut in over thousands of years is kept safe: plant remains, animal bones, microorganisms. But it seems that climate change is slowing this cooling system. Air temperatures are rising, twice as much as the global average. In the thawing soil, microbes are starting to break down carbon, which enters the atmosphere in the form of the greenhouses gases methane and carbon dioxide, further contributing to the heating up of the climate. The Russian-German Project “CarboPerm” drills down on this subsurface problem. Potsdam geophysicists help to look into the ground.
As Stephan Schennen and Jens Tronicke trudge through rough terrain, their feet sink into the mud. Every few decimeters, geophysical profile lines run across the surface. The muddy ground of the Great Lyakhovsky Island far in the North, in the Siberian Arctic, gives the researchers a hard time. With a ground-penetrating radar, they send electromagnetic waves into the ground and register travel time and amplitude of the reflected signals to make hidden geological structures visible. When a storm rolls in, the Potsdam geophysicists interrupt their work, as they do not want to risk damaging the sensitive devices. Spare parts cannot be obtained here. If anything goes wrong, everything will have been in vain.
In the summer of 2014, PhD student Stephan Schennen made his second trip to the Great Lyakhovsky Island to collect data for the CarboPerm project. Electromagnetic and geoelectric methods allow him to “look” up to 25 meters into the ground in an area the size of a football field. And while boreholes show the composition of the soil or its sediments at one particular point, his geophysical methods can map larger underground structures, even in 3D.
The idea to include geophysicists from the University of Potsdam in the investigations was a result of the close collaboration between researchers from Potsdam’s Alfred Wegener Institute/Helmholtz Centre for Polar and Ocean Research, who are in charge of the CarboPerm project, and the Institute of Soil Science of Hamburg University. For many years they have been researching Siberian permafrost landscapes with their Russian colleagues. Many drill cores were transported to laboratories, where they were analyzed layer by layer in order to reconstruct, for instance, the climate of past millennia. But they had no way of probing a larger area. “Our technologies permit us to explore and characterize the underground across a wide area,” says Jens Tronicke, Professor of Applied Geophysics at the University of Potsdam. “Be it in archaeology, geology, or engineering – geophysical methods can be applied anywhere, and now on permafrost soil, too.”
Under the auspices of the CarboPerm project, geophysicists from Potsdam work hand in hand with polar, oceanic, and atmospheric scientists, with geologists, biologists, and soil scientists and geochemists. It is the first time that such a comprehensive methodical approach has been applied in a permafrost region, with researchers analyzing the same samples, data, and measurements from one particular place in the Siberian Arctic. Together they want to find out more about the organic carbon that has been stored there for thousands of years, about its formation, turnover, and release as a result of global warming.
And the problem may indeed reach dramatic proportions: The permafrost soil covers as much as a quarter of the landmass of the northern hemisphere and holds 1,700 gigatons of carbon, that is about 2.5 times the amount of carbon in the global vegetation.
If temperatures continue to rise, will these gigantic Arctic carbon reservoirs turn into sources of carbon emissions? This is the question plaguing the project’s researchers. To find answers, they do not mind braving the harsh Arctic conditions.
The Great Lyakhovsky Island is nearly uninhabited. At camp at the mouth of a river, built by reindeer herders, the researches stay in wooden houses on skis, which can be moved in the winter on ice and snow. Even though the researchers arrive in the spring, temperatures can drop to -30°. For heating there is nothing more than a potbelly stove, Stephan Schennen explains. During his first visit in April 2014, it was still snowing. He had to interrupt his work many times to protect the sensitive measuring devices. “I had brought some spare parts, cables and plugs, and large rechargeable batteries, which lasted quite a while. In the end, I was very lucky; everything went fine.”
During the second measuring campaign last summer everything went according to plan, too. It does not get dark there at night, as the sun never sinks below the horizon, but that did not affect the sleep of the exhausted young geophysicist. As long as he was awake he was measuring. “If you know you have only three weeks and can’t come back easily, every minute counts.”
This spring Stephan Schennen went on his – for the moment – last trip to Siberia. This time he travelled to the Lena delta to take geophysical measurements on the islands of Samoylov and Kurungnakh. Back in his office, he displays 3D images of the surveyed underground on his laptop. An enormous amount of data has been collected and needs to be analyzed. He plans to finish his doctoral thesis by the autumn of 2016 when the CarboPerm project also ends. The project aims to more reliably forecast the development of permafrost soils and their contribution to the global carbon balance. At the International Permafrost Conference in Potsdam in 2016 the researchers will present their results.
Prof. Dr. Jens Tronicke studied geophysics in Münster. After being awarded his PhD in Tübingen, he researched at various universities in the US and at the ETH Zurich. Since 2005 he has worked as a Professor of Applied Geophysics at the University of Potsdam.
Institut für Erd- und Umweltwissenschaften
Stephan Schennen studied geosciences with a focus on geophysics in Bremen and Potsdam. Since 2013 he has been a doctoral student in the CarboPerm project.
“CarboPerm” is a three-year project comprising multidisciplinary investigations into the formation, turnover, and release of organic carbon in Siberian permafrost. Project partners are the Alfred Wegener Institute of Polar and Ocean Research, the universities of Potsdam, Hamburg and Cologne, the German Research Centre for Geosciences in Potsdam, the Max Planck Institute in Hamburg and Jena as well as Russian institutes. Research focuses on the effects of climate-induced and environmentally related changes on the sensitive terrestrial Arctic ecosystems and the natural production of greenhouse gases in tundra landscapes. The German Federal Ministry of Education and Research (BMBF) is funding the project with €4.5 million.
The Website: www.carboperm.net
This research is linked to the research initiative NEXUS: Earth Surface Dynamics, which clusters approaches from various scientific disciplines in the Berlin-Brandenburg area within the overarching theme of Earth surface dynamics. The University of Potsdam, along with its partnering institutions the Helmholtz-Centre Potsdam - German Research Centre for Geosciences (GFZ), the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) and partners from the Potsdam Institute for Climate Impact Research (PIK), the Museum für Naturkunde - Leibniz Institute for Evolution and Biodiversity Science (MfN) and the Technische Universität Berlin (TUB) therefore combines the outstanding expertise from geo-, bio-, climate and data sciences.
Text: Antje Horn-Conrad, Translation: Monika Wilke
Online-Editing: Agnes Bressa
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