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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 20 | Copyright
Biogeosciences, 15, 6033-6048, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Oct 2018

Research article | 15 Oct 2018

Organic matter characteristics in yedoma and thermokarst deposits on Baldwin Peninsula, west Alaska

Loeka L. Jongejans1, Jens Strauss1, Josefine Lenz1,2, Francien Peterse3, Kai Mangelsdorf4, Matthias Fuchs1,5, and Guido Grosse1,5 Loeka L. Jongejans et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Permafrost Research Section, Potsdam, Germany
  • 2University of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, AK, USA
  • 3Utrecht University, Department of Earth Sciences, Utrecht, the Netherlands
  • 4Helmholtz Centre Potsdam – German Research Centre for Geosciences, Potsdam, Germany
  • 5University of Potsdam, Institute of Earth and Environmental Sciences, Potsdam, Germany

Abstract. As Arctic warming continues and permafrost thaws, more soil and sedimentary organic matter (OM) will be decomposed in northern high latitudes. Still, uncertainties remain in the quality of the OM and the size of the organic carbon (OC) pools stored in different deposit types of permafrost landscapes. This study presents OM data from deep permafrost and lake deposits on the Baldwin Peninsula which is located in the southern portion of the continuous permafrost zone in west Alaska. Sediment samples from yedoma and drained thermokarst lake basin (DTLB) deposits as well as thermokarst lake sediments were analyzed for cryostratigraphical and biogeochemical parameters and their lipid biomarker composition to identify the belowground OC pool size and OM quality of ice-rich permafrost on the Baldwin Peninsula. We provide the first detailed characterization of yedoma deposits on Baldwin Peninsula. We show that three-quarters of soil OC in the frozen deposits of the study region (total of 68Mt) is stored in DTLB deposits (52Mt) and one-quarter in the frozen yedoma deposits (16Mt). The lake sediments contain a relatively small OC pool (4Mt), but have the highest volumetric OC content (93kgm−3) compared to the DTLB (35kgm−3) and yedoma deposits (8kgm−3), largely due to differences in the ground ice content. The biomarker analysis indicates that the OM in both yedoma and DTLB deposits is mainly of terrestrial origin. Nevertheless, the relatively high carbon preference index of plant leaf waxes in combination with a lack of a degradation trend with depth in the yedoma deposits indicates that OM stored in yedoma is less degraded than that stored in DTLB deposits. This suggests that OM in yedoma has a higher potential for decomposition upon thaw, despite the relatively small size of this pool. These findings show that the use of lipid biomarker analysis is valuable in the assessment of the potential future greenhouse gas emissions from thawing permafrost, especially because this area, close to the discontinuous permafrost boundary, is projected to thaw substantially within the 21st century.

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Short summary
Arctic warming mobilizes belowground organic matter in northern high latitudes. This study focused on the size of organic carbon pools and organic matter quality in ice-rich permafrost on the Baldwin Peninsula, West Alaska. We analyzed biogeochemistry and found that three-quarters of the carbon is stored in degraded permafrost deposits. Nonetheless, using biomarker analyses, we showed that the organic matter in undisturbed yedoma permafrost has a higher potential for decomposition.
Arctic warming mobilizes belowground organic matter in northern high latitudes. This study...