Old Organic Matter in Siberian Permafrost Deposits and its Degradation Features

• Main Authors: Strauss, Jens, Schirrmeister, Lutz, Wetterich, Sebastian, Mangelsdorf, Kai
• Format: Conference Object
• Language: unknown
• Published: The Fort Dialog-Iset Publisher 2012
• Subjects: Arctic; Khaya; Buor-Khaya; Global warming; Ice; permafrost; Thermokarst; Yakutia
• Online Access: https://epic.awi.de/id/eprint/30849/; https://epic.awi.de/id/eprint/30849/1/Strauss_abstract_TICOP.pdf; https://hdl.handle.net/10013/epic.39819; https://hdl.handle.net/10013/epic.39819.d001

Introduction During the late Quaternary, a large pool of organic matter (OM) accumulated in the arctic permafrost zone. Because of the potential re-introduction into the biogeochemical cycle from degrading permafrost, the OC inventory of ice-rich permafrost deposits and its degradation features are relevant to current concerns about the effects of global warming. The objectives of this paper are (1) to deduce the quality and quantity of OM stored in the studied sedi-ments and (2) to infer the paleoenvironmental condi-tions of the source biota. Therefore, standard sedimentological and a molecular marker (biomarker) approach are applied. Methods The study site is located on the west coast of the Buor Khaya Peninsula (N 71.6°, E 132.2°, Fig. 1), Yakutia (Russia). In Table 1 the used methods are summarized. Table 1. Applied methods Parameter Analyses and methods Radiocarbon age AMS 14C Grain size Diffraction Particle Size Ana-lyzer Bulk density Gas pycnometer OM characteristics (TOC, C/N, δ13C) Element analyses Mass -spectrometry Isotope signature of ground ice (δ18O, δ2H) Mass -spectrometry Biomarkers (brGDGT, archaeol, n-alkanes) HPLC-MS GC-MS Hydrobiochemistry (Acetate) Ion chromatography Results and Discussion Stratigraphically, two sediment units are distin-guished. The first unit is composed of late Pleistocene ice-rich permafrost (Yedoma). The second unit consists of Holocene thermokarst deposits. The mean bulk den-sity is ca. 1 10³kg/m³. The average total organic carbon (TOC) content is 2.4 wt% for Yedoma, 2.8 wt% for thermokarst deposits. The OM is low degraded (mean C/N 10) for mineral sediments. Hence, the deposits ac-cumulated at relatively fast rates and the OM underwent a short time of decomposition before it was incorporated into permafrost. The volumetric organic carbon contents of the Yedoma and thermokarst deposits are 13 ± 11 kg/m³ and 22 ± 11 kg/m³, re-spectively. This quantity is inside the range of comparable deposits studied by Schirrmeister et al. (2011). δ13C reveal a terrestrial signal ...