Preprints
https://doi.org/10.5194/tc-2022-12
https://doi.org/10.5194/tc-2022-12
 
16 Mar 2022
16 Mar 2022
Status: this preprint is currently under review for the journal TC.

Assessing Organic Matter Characteristics in Ancient Permafrost: A Biogeochemical Study at the Batagay Megaslump, East Siberia

Loeka Laura Jongejans1,2, Kai Mangelsdorf3, Cornelia Karger3, Thomas Opel4, Sebastian Wetterich1,a, Jérémy Courtin2,4, Hanno Meyer4, Alexander I. Kizyakov5, Guido Grosse1,2, Andrei G. Shepelev6, Igor I. Syromyatnikov7, Alexander N. Fedorov6, and Jens Strauss1 Loeka Laura Jongejans et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Permafrost Research Section, 14473 Potsdam, Germany
  • 2Institute of Geosciences, University of Potsdam, 14476 Potsdam, Germany
  • 3GFZ German Research Centre for Geosciences, Section Organic Geochemistry, 14473 Potsdam, Germany
  • 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Polar Terrestrial Environmental Systems Section, 14473 Potsdam, Germany
  • 5Cryolithology and Glaciology Department, Faculty of Geography, Lomonosov Moscow State University, 119991 Moscow
  • 6Laboratory of Permafrost Landscapes, Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk, Russia
  • 7Laboratory of General Geocryology, Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk
  • acurrent address: Technische Universität Dresden, Institute of Geography, 01069 Dresden, Germany

Abstract. The Batagay megaslump, a permafrost thaw feature in northeastern Siberia, provides access to ancient permafrost up to ~650 ka old. We aimed to assess the permafrost-locked organic matter (OM) quality and to deduce paleoenvironmental information on glacial-interglacial timescales. We sampled five stratigraphic units exposed on the 55-m-high slump headwall and analyzed lipid biomarkers. Our findings revealed similar biogeochemical signatures for the glacial periods: the Lower Ice Complex (Marine Isotope Stage (MIS) 16 or earlier), the Lower Sand Unit (some time between MIS 16-6) and the Upper Ice Complex (MIS 4-2). The OM in these units has a terrestrial character, and microbial activity was likely limited. Contrarily, the n-alkane and fatty acid distributions differed for the units from interglacial periods: the Woody Layer (MIS 5), separating the Lower Sand and the Upper Ice Complex, and the Holocene Cover (MIS 1), on top of the Upper Ice Complex. The Woody Layer, marking an permafrost degradation disconformity, contained markers of terrestrial origin (sterols) and high microbial decomposition (iso- and anteiso-fatty acids). In the Holocene Cover, biomarkers pointed to wet depositional conditions and we identified branched and cyclic alkanes, which are likely of microbial or bacterial origin. Higher OM decomposition characterized the interglacial periods. As climate warming will continue permafrost degradation in the Batagay megaslump and in other areas, large amounts of deeply buried, ancient OM with a variable composition and degradability are mobilized, likely significantly enhancing greenhouse gas emissions from permafrost regions.

Loeka Laura Jongejans et al.

Status: open (until 10 Jun 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-12', Jack Hutchings, 02 May 2022 reply
  • RC2: 'Comment on tc-2022-12', Anonymous Referee #2, 08 May 2022 reply

Loeka Laura Jongejans et al.

Loeka Laura Jongejans et al.

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Short summary
Large parts of Arctic Siberia are underlain by permafrost. Climate warming leads to permafrost thaw. At the Batagay megaslump, permafrost sediments up to ~650 ka old are exposed. We took sediment samples and analyzed the organic matter (e.g., plant remains). We found distinct differences in the biomarker distributions between the glacial and interglacial deposits with generally stronger microbial activity during interglacial periods. Further permafrost thaw enhances greenhouse gas emissions.