Volume 15, issue 17 | Copyright
Biogeosciences, 15, 5423-5436, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Sep 2018

Research article | 13 Sep 2018

Greenhouse gas production in degrading ice-rich permafrost deposits in northeastern Siberia

Josefine Walz1,2, Christian Knoblauch1,2, Ronja Tigges1, Thomas Opel3,4, Lutz Schirrmeister4, and Eva-Maria Pfeiffer1,2 Josefine Walz et al.
  • 1Institute of Soil Science, Universität Hamburg, 20146 Hamburg, Germany
  • 2Center for Earth System Research and Sustainability, Universität Hamburg, 20146 Hamburg, Germany
  • 3Permafrost Laboratory, Department of Geography, University of Sussex, Brighton, BN1 9RH, UK
  • 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 14473 Potsdam, Germany

Abstract. Permafrost deposits have been a sink for atmospheric carbon for millennia. Thaw-erosional processes, however, can lead to rapid degradation of ice-rich permafrost and the release of substantial amounts of organic carbon (OC). The amount of the OC stored in these deposits and their potential to be microbially decomposed to the greenhouse gases carbon dioxide (CO2) and methane (CH4) depends on climatic and environmental conditions during deposition and the decomposition history before incorporation into the permafrost. Here, we examine potential greenhouse gas production as a result of degrading ice-rich permafrost deposits from three locations in the northeastern Siberian Laptev Sea region. The deposits span a period of about 55kyr from the last glacial period and Holocene interglacial. Samples from all three locations were incubated under aerobic and anaerobic conditions for 134 days at 4°C. Greenhouse gas production was generally higher in deposits from glacial periods, where 0.2%–6.1% of the initially available OC was decomposed to CO2. In contrast, only 0.1%–4.0% of initial OC was decomposed in permafrost deposits from the Holocene and the late glacial transition. Within the deposits from the Kargin interstadial period (Marine Isotope Stage 3), local depositional environments, especially soil moisture, also affected the preservation of OC. Sediments deposited under wet conditions contained more labile OC and thus produced more greenhouse gases than sediments deposited under drier conditions. To assess the greenhouse gas production potentials over longer periods, deposits from two locations were incubated for a total of 785 days. However, more than 50% of total CO2 production over 785 days occurred within the first 134 days under aerobic conditions, while 80% were produced over the same period under anaerobic conditions, which emphasizes the nonlinearity of the OC decomposition processes. Methanogenesis was generally observed in active layer samples but only sporadically in permafrost samples and was several orders of magnitude smaller than CO2 production.

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Short summary
We investigate potential CO2 and CH4 production in degrading ice-rich permafrost in northeastern Siberia, deposited under different climatic conditions. With laboratory incubations, it could be shown that Late Pleistocene yedoma deposits generally produced more CO2 than Holocene deposits. Thus, OM decomposability needs to be interpreted against the paleoenvironmental background. However, OM decomposability cannot be generalized solely based on the stratigraphic position.
We investigate potential CO2 and CH4 production in degrading ice-rich permafrost in northeastern...