EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Vulnerability of subsea permafrost organic matter to degradation after thaw

Birgit Wild1,2, Natalia Shakhova3, Oleg Dudarev3,4, Alexey Ruban3, Denis Kosmach4, Vladimir Tumskoy5,6,7, Tommaso Tesi8, Hanna Joß1, Helena Alexanderson9,10, Martin Jakobsson2,11, Alexey Mazurov3, Igor Semiletov3,4, and Örjan Gustafsson1,2
Birgit Wild et al.
  • 1Department of Environmental Science, Stockholm University, Stockholm, Sweden (
  • 2Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 3Tomsk Polytechnic University, Tomsk, Russia
  • 4Pacific Oceanological Institute, Russian Academy of Sciences, Vladivostok, Russia
  • 5Moscow State University, Moscow, Russia
  • 6Institute of Geography, Russian Academy of Sciences, Moscow, Russia
  • 7University of Tyumen, Tyumen, Russia
  • 8Institute of Polar Sciences, National Research Council, Bologna, Italy
  • 9Department of Geology, Lund University, Lund, Sweden
  • 10Department of Geosciences, UiT Arctic University of Norway, Tromsø, Norway
  • 11Department of Geological Sciences, Stockholm University, Stockholm, Sweden

Subsea permafrost contains a potentially large and vulnerable organic carbon pool that might be or become a source of greenhouse gases to the atmosphere. While organic carbon stocks and vulnerability of terrestrial permafrost are increasingly well constrained, the dynamics of subsea permafrost remain highly uncertain due to limited observational data from these hard-to-access systems. Based on a unique set of drill cores from the near-coastal Laptev Sea, we here assess the vulnerability of subsea permafrost organic matter to degradation after thaw. To that end, we combine biomarker analyses of organic matter above and below the in-situ thaw front with incubation of subsea permafrost material in the laboratory. Biomarker degradation proxies based on the lignin phenol composition of organic matter (acid/aldehyde ratios of syringyl and vanillyl phenols; 3,5-dihydroxybenzoic acid/vanillyl ratio) suggest an overall low degradation state of lignin compared to terrestrial permafrost deposits and marine sediments in the region, and no systematic change across the thaw front. These lignin-based proxies are mostly sensitive to degradation under oxic conditions, i.e. before organic matter burial in subsea permafrost deposits, and less to degradation under anoxic conditions that prevail at the thaw front of subsea permafrost. Lignin phenol proxies will therefore be complemented by other biomarker degradation proxies sensitive to degradation under anoxic conditions, as well as by first data from incubation of subsea permafrost material under cold, anoxic conditions. Together, these data will enhance our understanding of organic matter in subsea permafrost, its vulnerability to degradation after thaw and the potential for greenhouse gas emissions from this system.

How to cite: Wild, B., Shakhova, N., Dudarev, O., Ruban, A., Kosmach, D., Tumskoy, V., Tesi, T., Joß, H., Alexanderson, H., Jakobsson, M., Mazurov, A., Semiletov, I., and Gustafsson, Ö.: Vulnerability of subsea permafrost organic matter to degradation after thaw, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17935,, 2020