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.

Description: A new version (2022) is available: https://doi.org/10.1594/PANGAEA.946915 Marine particulate organic carbon-13 stable isotope ratios (δ13CPOC) provide additional constraints and insights on the cycling of carbon from dissolved pools to the marine ecosystem including anthropogenic contributions. For such purposes, robust spatio-temporal coverage of δ13CPOC observations is essential. We collected all such available known data sets, merged and uniformed them to provide – to the best of our knowledge – the largest available marine δ13CPOC data set. The data set consists of 4732 data points covering all major ocean basins from the 1960s to 2010s. We provide the data in twenty-one different files for best direct application on specific research purposes: a csv file including the 4732 δ13CPOC measurements, their anomalies relative to their mean −23.96 ‰ as well as all available meta-information a NetCDF file including an interpolation onto the 1°x1°-resolution grid based on the World Ocean Atlas (WOA18) data product of all δ13CPOC measurements with full spatio-temporal metadata, averaging all observations from each year together, each year accounting for a time increment on the time axis twelve NetCDF files - one for each month of the year - including an interpolation onto the 1°x1°-resolution grid based on the World Ocean Atlas (WOA18) data product of all δ13CPOC measurements with full spatio-temporal metadata, averaging only observations from the respective month, each year accounting for a time increment on the time axis a NetCDF file including an interpolation onto a 1.8°x3.6°-resolution grid of a δ13CPOC simulating model of all δ13CPOC measurements with full spatial metadata six NetCDF files – one for each decade between the 1960s and 2010s – including an interpolation onto the 1.8°x3.6°-resolution grid of a δ13CPOC simulating model of all δ13CPOC measurements with full spatial metadata and available sample year information