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  • 2020-2024  (34)
  • 2010-2014  (17)
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  • 1
    Publication Date: 2023-02-08
    Description: Highlights • Previous age estimates of the Laacher See Eruptions (LSE) around 12,900 years are still diverging and imprecise. • The combination of dendrochronology, wood anatomy, and 14C measurements holds the potential to establish a precise LSE date. • An absolute calendric date of the LSE would improve the synchronization of European Late Glacial to Holocene archives. Abstract The precise date of the Laacher See eruption (LSE), central Europe’s largest Late Pleistocene volcanic event that occurred around 13,000 years ago, is still unknown. Here, we outline the potential of combined high-resolution dendrochronological, wood anatomical and radiocarbon (14C) measurements, to refine the age of this major Plinian eruption. Based on excavated, subfossil trees that were killed during the explosive LSE and buried under its pyroclastic deposits, we describe how a firm date of the eruption might be achieved, and how the resulting temporal precision would further advance our understanding of the environmental and societal impacts of this event. Moreover, we discuss the relevance of an accurate LSE date for improving the synchronization of European terrestrial and lacustrine Late Glacial to Holocene archives.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2024-02-07
    Description: Radiocarbon (14C), as a consequence of its production in the atmosphere and subsequent dispersal through the carbon cycle, is a key tracer for studying the Earth system. Knowledge of past 14C levels improves our understanding of climate processes, the Sun, the geodynamo, and the carbon cycle. Recently updated radiocarbon calibration curves (IntCal20, SHCal20, and Marine20) provide unprecedented accuracy in our estimates of 14C levels back to the limit of the 14C technique (~55,000 years ago). Such improved detail creates new opportunities to probe the Earth and climate system more reliably and at finer scale. We summarize the advances that have underpinned this revised set of radiocarbon calibration curves, survey the broad scientific landscape where additional detail on past 14C provides insight, and identify open challenges for the future.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2014-09-03
    Description: Throughout the transition from the last Glacial to the current Interglacial, rising atmospheric CO2 levels were accompanied by declining atmospheric Δ14C values. A likely mechanism, influencing both components is the deglacial release of CO2, stored for millennia in the deep Ocean, to the atmosphere. Due to its long residence time within the oceans interior this CO2 rich water mass was considerably depleted in radiocarbon. Although a large number of studies address this topic, the extent, location and pathways of the glacial carbon pool are still subjects of an ongoing debate. As deep water masses are upwelled and new intermediate waters are formed around Antarctica, the Southern Ocean is a potential area for the deglacial release of stored CO2. Here we present radiocarbon and carbonate ion data from a transect of sediment cores off New Zealand that covers the major water masses in this area, from the AAIW down to the AABW. During the Glacial, our data locate a significantly 14C depleted pool in a water depth between 2000 and 4500 m. The combination of Δ14C and [CO32-] records provides new insights into the process of oceanic-atmospheric CO2 exchange in the Southern Ocean. In addition, our results yield new implications for contradicting Δ14C records from the Southern Ocean and lower latitudes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
    Publication Date: 2018-08-10
    Description: Defining the extent of the Last Glacial Maximum Antarctic Ice Sheet and the timing of its subsequent retreat still remains poorly understood for numerous drainage sectors. New marine geoscientific field data from a formerly unstudied West Antarctic continental shelf sector reveal the last maximum extent of the ice sheet and its initial retreat. It is shown how modern continental shelf regions must have already been evacuated at a remarkably early stage, thereby validating a rather diachronous retreat pattern of the Antarctic Ice Sheet following its last maximum extent.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
    Publication Date: 2018-08-10
    Description: High-resolution swath bathymetry data collected during several research cruises over the past two decades reveal a palaeo-ice stream trough (Abbot Glacial Trough) crossing the middle and outer shelf of the easternmost Amundsen Sea Embayment, east of the main Pine Island Trough. Regions of both fast palaeo-ice flow (within the central trough) and slow palaeo-ice flow (on adjacent seafloor highs referred to as inter-ice stream ridges) bear glacial landforms indicative of phases of grounding-line stabilization of the ice sheet. We associate a grounding-zone wedge situated within the outer Abbot Glacial Trough with a grounding-zone wedge in outer Pine Island Trough and suggest a synchronous grounding-line halt in both troughs. New sediment echosounder and sediment core data collected from outer Abbot Glacial Trough, between the seaward limit of the grounding-zone wedge and the shelf edge, reveal an up to 6 m-thick well stratified drape that is composed of unconsolidated glaciomarine sediments occasionally bearing calcareous microfossils. In order to decipher whether this unusually thick sediment drape might indicate sub-ice shelf and/or seasonal-open marine deposition throughout or since the Last Glacial Maximum, we used a multi-proxy approach to characterize its lithofacies and applied radiocarbon dating of calcareous microfossils. Here we present our initial results and discuss since when the outer shelf in the eastern Amundsen Sea has been free of grounded-ice. Such information will 1) improve ice sheet models that aim to reconstruct the flow and extent of the West Antarctic Ice Sheet during the Last Glacial Maximum, 2) help to quantify the ice volume of the West Antarctic Ice Sheet during this time, and 3) prove or reject the possibility that Antarctic benthic biota endured glacial periods in outer shelf refugia.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 6
    Publication Date: 2018-08-10
    Description: Recent palaeoglaciological studies on the West Antarctic shelf have mainly focused on the wide embayments of the Ross and Amundsen seas in order to reconstruct the extent and subsequent retreat of the West Antarctic Ice Sheet (WAIS) since the Last Glacial Maximum (LGM). However, the narrower shelf sectors between these two major embayments have remained largely unstudied in previous geological investigations despite them covering extensive areas of the West Antarctic shelf. Here, we present the first systematic marine geological and geophysical survey of a shelf sector offshore from the Hobbs Coast. It is dominated by a large grounding zone wedge (GZW), which fills the base of a palaeo-ice stream trough on the inner shelf and marks a phase of stabilization of the grounding line during general WAIS retreat following the last maximum ice-sheet extent in this particular area (referred to as the Local Last Glacial Maximum, ‘LLGM’). Reliable age determination on calcareous microfossils from the infill of a subglacial meltwater channel eroded into the GZW reveals that grounded ice had retreated landward of the GZW before ∼20.88 cal. ka BP, with deglaciation of the innermost shelf occurring prior to ∼12.97 cal. ka BP. Geophysical sub-bottom information from the inner-, mid- and outer shelf indicates grounded ice extended to the shelf edge prior to the formation of the GZW. Assuming the wedge was deposited during deglaciation, we infer the timing of maximum grounded ice extent occurred before ∼20.88 cal. ka BP. This could suggest that the WAIS retreat from the outer shelf was already underway during or even prior to the global LGM (∼23–19 cal. ka BP). Our new findings give insights into the regional deglacial behaviour of this understudied part of the West Antarctic shelf and at the same time support early deglaciation ages recently presented for adjacent drainage sectors of the WAIS. If correct, these findings contrast with the hypothesis that initial deglaciation of Antarctic Ice Sheets occurred synchronously at ∼19 cal. ka BP.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Rapid Communications in Mass Spectrometry 26 (2012): 2619–2626, doi:10.1002/rcm.6385.
    Description: Steroids are potent hormones that are found in many environments. Yet, contributions from synthetic and endogenous sources are largely uncharacterized. The goal of this study was to evaluate whether carbon isotopes could be used to distinguish between synthetic and endogenous steroids in wastewater and other environmental matrices. Estrogens and progestogens were isolated from oral contraceptive pills using semi-preparative liquid chromatography/diode array detection (LC/DAD). Compound purity was confirmed by gas chromatography-flame ionization detection (GC-FID), gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) and liquid chromatography/mass spectrometry using negative electrospray ionization (LC/ESI-MS). 13C content was determined by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and 14C was measured by accelerator mass spectrometry (AMS). Synthetic estrogens and progestogens are 13C depleted (δ13Cestrogen = -30.0 ± 0.9 ‰; δ13Cprogestogen = -30.3 ± 2.6 ‰) compared to endogenous hormones (δ13C ~ -16 ‰ to -26 ‰). The 14C content of the majority of synthetic hormones is consistent with synthesis from C3 plant-based precursors, amended with “fossil” carbon in the case of EE2 and norethindrone acetate. Exceptions are progestogens that contain an ethyl group at carbon position 13 and have entirely “fossil” 14C signatures. Carbon isotope measurements have the potential to distinguish between synthetic and endogenous hormones in the environment. Our results suggest that 13C could be used to discriminate endogenous from synthetic estrogens in animal waste, wastewater effluent, and natural waters. In contrast, 13C and 14C together may prove useful for tracking synthetic progestogens.
    Description: This work was supported by the Martin Family Society of Fellows for Sustainability and by a U.S. Environmental Protection Agency STAR graduate fellowship (FP-91713401).
    Keywords: Steroidal hormones ; Ethynylestradiol (EE2) ; Carbon isotopes (13C, 14C) ; Oral contraceptive pill ; Environmental forensics
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 8
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 110 (2013): 14168–14173, doi:10.1073/pnas.1307031110.
    Description: Mobilization of Arctic permafrost carbon is expected to increase with warming-induced thawing. However, this effect is challenging to assess due to the diverse processes controlling the release of various organic carbon (OC) pools from heterogeneous Arctic landscapes. Here, by radiocarbon dating various terrestrial OC components in fluvially- and coastally-integrated estuarine sediments, we present a unique framework for deconvoluting the contrasting mobilization mechanisms of surface versus deep (permafrost) carbon pools across the climosequence of the Eurasian Arctic. Vascular-plant-derived lignin phenol 14C contents reveal significant inputs of young carbon from surface sources whose delivery is dominantly controlled by river runoff. In contrast, plant wax lipids predominantly trace ancient (permafrost) OC that is preferentially mobilized from discontinuous permafrost regions where hydrological conduits penetrate deeper into soils and thermokarst erosion occurs more frequently. As river runoff has significantly increased across the Eurasian Arctic in recent decades, we estimate from an isotopic mixing model that, in tandem with an increased transfer of young surface carbon, the proportion of mobilized terrestrial OC accounted for by ancient carbon has increased by 3-6% between 1985-2004. These findings suggest that, while partly masked by surface-carbon export, climate-change-induced mobilization of old permafrost carbon is well under way in the Arctic.
    Description: The ISSS program is supported by the Knut and Alice Wallenberg Foundation, the Far Eastern Branch of the Russian Academy of Sciences, the Swedish Research Council, the US National Oceanic and Atmospheric Administration, the Russian Foundation of Basic Research, the Swedish Polar Research Secretariat and the Nordic Council of Ministers (Arctic Co-Op and TRI-DEFROST programs). Ö.G. acknowledges an Academy Research Fellow grant from the Swedish Royal Academy of Sciences. Grants OCE-9907129, OCE-0137005, and OCE-0526268 from the US National Science Foundation (NSF), the Stanley Watson Chair for Excellence in Oceanography (to T.I.E.) and ETH Zürich enabled this research. J.E.V. thanks support from NWO-Rubicon (#825.10.022). B.E.v.D thanks support from the UK NERC (NE/I024798/1). X.F. thanks WHOI for a postdoctoral scholar fellowship and for postdoctoral support from ETH Zürich.
    Description: 2014-01-01
    Keywords: Fluvial mobilization ; Compound-specific 14C ; Hydrogeographic control
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 9
    Publication Date: 2023-04-22
    Description: Compound-specific radiocarbon dating often requires working with small samples of 〈 100 µg carbon (µgC). This makes the radiocarbon dates of biomarker compounds very sensitive to biases caused by extraneous carbon of unknown composition, a procedural blank, which is introduced to the samples during the steps necessary to prepare a sample for radiocarbon analysis by accelerator mass spectrometry (i.e., isolating single compounds from a heterogeneous mixture, combustion, gas purification and graphitization). Reporting accurate radiocarbon dates thus requires a correction for the procedural blank. We present our approach to assess the fraction modern carbon (F14C) and the mass of the procedural blanks introduced during the preparation procedures of lipid biomarkers (i.e. n-alkanoic acids) and lignin phenols. We isolated differently sized aliquots (6-151 µgC) of n-alkanoic acids and lignin phenols obtained from standard materials with known F14C values. Each compound class was extracted from two standard materials (one fossil, one modern) and purified using the same procedures as for natural samples of unknown F14C. There was an inverse linear relationship between the measured F14C values of the processed aliquots and their mass, which suggests constant contamination during processing of individual samples. We used Bayesian methods to fit linear regression lines between F14C and 1/mass for the fossil and modern standards. The intersection points of these lines were used to infer F14Cblank and mblank and their associated uncertainties. We estimated 4.88±0.69 μgC of procedural blank with F14C of 0.714±0.077 for n-alkanoic acids, and 0.90±0.23 μgC of procedural blank with F14C of 0.813±0.155 for lignin phenols. These F14Cblank and mblank can be used to correct AMS results of lipid and lignin samples by isotopic mass balance. This method may serve as a standardized procedure for blank assessment in small-scale radiocarbon analysis.
    Keywords: AWI_Envi; Center for Marine Environmental Sciences; MARUM; Polar Terrestrial Environmental Systems @ AWI
    Type: Dataset
    Format: application/zip, 2.5 MBytes
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  • 10
    Publication Date: 2023-04-22
    Keywords: AWI_Envi; Compounds; Event label; Fraction modern carbon; Fraction modern carbon, standard deviation; Laboratory code/label; Mass; Mass, standard deviation; Messel_oil_shale; Messel, Germany; OUTCROP; Outcrop sample; Polar Terrestrial Environmental Systems @ AWI; Type
    Type: Dataset
    Format: text/tab-separated-values, 205 data points
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