Publication Date:
2024-05-07
Description:
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.
Keywords:
AWI Arctic Land Expedition; Biomarker; CACOON; Carbon; Changing Arctic Carbon cycle in the cOastal Ocean Near-shore; erosion; Event label; Height above river level; n-alkane; n-Alkane C14, per unit mass total organic carbon; n-Alkane C14, per unit sediment mass; n-Alkane C15, per unit mass total organic carbon; n-Alkane C15, per unit sediment mass; n-Alkane C16, per unit mass total organic carbon; n-Alkane C16, per unit sediment mass; n-Alkane C17, per unit mass total organic carbon; n-Alkane C17, per unit sediment mass; n-Alkane C18, per unit mass total organic carbon; n-Alkane C18, per unit sediment mass; n-Alkane C19, per unit mass total organic carbon; n-Alkane C19, per unit sediment mass; n-Alkane C20, per unit mass total organic carbon; n-Alkane C20, per unit sediment mass; n-Alkane C21, per unit mass total organic carbon; n-Alkane C21, per unit sediment mass; n-Alkane C22, per unit mass total organic carbon; n-Alkane C22, per unit sediment mass; n-Alkane C23, per unit mass total organic carbon; n-Alkane C23, per unit sediment mass; n-Alkane C24, per unit mass total organic carbon; n-Alkane C24, per unit sediment mass; n-Alkane C25, per unit mass total organic carbon; n-Alkane C25, per unit sediment mass; n-Alkane C26, per unit mass total organic carbon; n-Alkane C26, per unit sediment mass; n-Alkane C27, per unit mass total organic carbon; n-Alkane C27, per unit sediment mass; n-Alkane C28, per unit mass total organic carbon; n-Alkane C28, per unit sediment mass; n-Alkane C29, per unit mass total organic carbon; n-Alkane C29, per unit sediment mass; n-Alkane C30, per unit mass total organic carbon; n-Alkane C30, per unit sediment mass; n-Alkane C31, per unit mass total organic carbon; n-Alkane C31, per unit sediment mass; n-Alkane C32, per unit mass total organic carbon; n-Alkane C32, per unit sediment mass; n-Alkane C33, per unit mass total organic carbon; n-Alkane C33, per unit sediment mass; n-Alkane C34, per unit mass total organic carbon; n-Alkane C34, per unit sediment mass; n-Alkane C35, per unit mass total organic carbon; n-Alkane C35, per unit sediment mass; n-fatty acids; PERM; RU-Land_2018_Lena_Sobo-Sise; Sample ID; Sampling permafrost; Siberia; SOB18-01; SOB18-03; SOB18-06; Sobo-Sise 2018; Sobo-Sise Island; Yedoma
Type:
Dataset
Format:
text/tab-separated-values, 1294 data points
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