n-Alkane composition of organic matter in a rapidly eroding permafrost cliff


Organic carbon (OC) stored in Arctic permafrost represents one of Earth’s largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coasts are particularly susceptible to thawing processes. Accelerating erosion of terrestrial permafrost along shorelines leads to increased transfer of organic matter (OM) to nearshore waters. However, the amount of terrestrial permafrost carbon and nitrogen as well as the OM quality in these deposits are still poorly quantified. Here, we characterise the sources and the quality of OM supplied to the Lena River at a rapidly eroding permafrost river shoreline cliff in the eastern part of the delta (Sobo-Sise Island). Our multi-proxy approach captures bulk elemental, molecular geochemical and carbon isotopic analyses of late Pleistocene Yedoma permafrost and Holocene cover deposits, discontinuously spanning the last ~52 ka. We show that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt%).We found that the OM quality, which we define as the intrinsic potential to further transformation, decomposition, and mineralization, is also high as inferred by the lipid biomarker inventory. The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal kyr BP) and is overlaid by Last Glacial MIS 2 (dated to 28 to 15 cal ka BP) and Holocene MIS 1 (dated to 7–0 cal ka BP) deposits. The relatively high average chain length (ACL) index of n-alkanes along the cliff profile indicates a predominant contribution of vascular plants to the OM composition. The elevated ratio of iso and anteiso-branched FAs relative to long chain (C ≥ 20) n-FAs in the interstadial MIS 3 and the interglacial MIS 1 deposits, suggests stronger microbial activity and consequently higher input of bacterial biomass during these climatically warmer periods. The overall high carbon preference index (CPI) and higher plant fatty acid (HPFA) values as well as high C / N ratios point to a good quality of the preserved OM and thus to a high potential of the OM for decomposition upon thaw. A decrease of HPFA values downwards along the profile probably indicates a relatively stronger OM decomposition in the oldest (MIS 3) deposits of the cliff.

DOI https://doi.org/10.1594/PANGAEA.935658
Related Identifier https://doi.org/10.1594/PANGAEA.935672
Related Identifier https://doi.org/10.5194/bg-19-2079-2022
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.935658
Creator Haugk, Charlotte; Jongejans, Loeka Laura; Mangelsdorf, Kai; Fuchs, Matthias; Ogneva, Olga; Palmtag, Juri; Mollenhauer, Gesine; Mann, Paul James; Overduin, Pier Paul; Grosse, Guido; Sanders, Tina; Tuerena, Robyn E; Schirrmeister, Lutz; Wetterich, Sebastian; Kizyakov, Alexander; Strauss, Jens
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2021
Funding Reference Federal Ministry of Education and Research, 03F0806A; Natural Environment Research Council, NE R012806 1
Rights Creative Commons Attribution 4.0 International; https://creativecommons.org/licenses/by/4.0/
OpenAccess true
Language English
Resource Type Dataset
Format text/tab-separated-values
Size 1294 data points
Discipline Earth System Research
Spatial Coverage (128.280W, 72.538S, 128.283E, 72.539N); Sobo-Sise Island
Temporal Coverage Begin 2018-07-14T00:00:00Z
Temporal Coverage End 2018-07-18T00:00:00Z