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  • Articles  (26)
  • Cambridge University Press  (13)
  • John Wiley & Sons  (9)
  • Nature Publishing Group  (4)
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  • Articles  (26)
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  • 11
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    Radiocarbon Dating of Individual Fatty Acids as a Tool for Refining Antarctic Margin Sediment Chronologies (2003)
    Cambridge University Press
    Details
    Publication Date: 2003-01-01
    Description: We have measured the radiocarbon contents of individual, solvent-extractable, short-chain (C14, C16, and C18) fatty acids isolated from Ross Sea surface sediments. The corresponding 14C ages are equivalent to that of the post-bomb dissolved inorganic carbon (DIC) reservoir. Moreover, molecular 14C variations in surficial (upper 15 cm) sediments indicate that these compounds may prove useful for reconstructing chronologies of Antarctic margin sediments containing uncertain (and potentially variable) quantities of relict organic carbon. A preliminary molecular 14C chronology suggests that the accumulation rate of relict organic matter has not changed during the last 500 14C yr. The focus of this study is to determine the validity of compound-specific 14C analysis as a technique for reconstructing chronologies of Antarctic margin sediments.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 12
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    Radiocarbon Dating of Alkenones from Marine Sediments: III. Influence of Solvent Extraction Procedures on 14C Measurements of Foraminifera (2005)
    Cambridge University Press
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    Publication Date: 2005-01-01
    Description: As a result of the growing use of multiple geochemical proxies to reconstruct ocean and climate changes in the past, there is an increasing need to establish temporal relationships between proxies derived from the same marine sediment record and ideally from the same core sections. Coupled proxy records of surface ocean properties, such as those based on lipid biomarkers (e.g. alkenone-derived sea surface temperature) and planktonic foraminiferal carbonate (oxygen isotopes), are a key example. Here, we assess whether 2 different solvent extraction procedures used for isolation of molecular biomarkers influence the radiocarbon contents of planktonic foraminiferal carbonate recovered from the corresponding residues of Bermuda Rise and Cariaco Basin sediments. Although minor Δ14C differences were observed between solvent-extracted and unextracted samples, no substantial or systematic offsets were evident. Overall, these data suggest that, in a practical sense, foraminiferal shells from a solvent-extracted residue can be reliably used for 14C dating to determine the age of sediment deposition and to examine age relationships with other sedimentary constituents (e.g. alkenones).
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 13
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    Radiocarbon Dating of Alkenones from Marine Sediments: II. Assessment of Carbon Process Blanks (2005)
    Cambridge University Press
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    Publication Date: 2005-01-01
    Description: We evaluate potential process blanks associated with radiocarbon measurement of microgram to milligram quantities of alkenones at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. Two strategies to constrain the contribution of blanks to alkenone 14C dates were followed: 1) dating of samples of known age and 2) multiple measurements of identical samples. We show that the potential contamination associated with the procedure does not lead to a systematic bias of the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record Δ14C of ambient DIC with an accuracy of approximately 10‰. A conservative estimate of measurement precision is 17‰ for modern samples. Alkenone 14C ages are expected to be reliable within 500 yr for samples younger than 10,500 14C yr.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 14
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    Dimensions of Radiocarbon Variability within Sedimentary Organic Matter (2018)
    Cambridge University Press
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    Publication Date: 2018-05-30
    Description: Organic carbon (OC) radiocarbon (14C) signatures in marine surface sediments are highly variable and the causes of this heterogeneity remain ambiguous. Here, we present results from a detailed 14C-based investigation of an Arabian Sea sediment, including measurements on organic matter (OM) in bulk sediment, specific grain size fractions, and OC decomposition products from ramped-pyrolysis-oxidation (RPO). Our results show that 14C ages of OM increase with increasing grain size, suggesting that grain size is an important factor controlling the 14C heterogeneity in marine sediments. Analysis of RPO decomposition products from different grain size fractions reveals an overall increase in age of corresponding thermal fractions from finer to coarser fractions. We suggest that hydrodynamic properties of sediment grains exert the important control on the 14C age distribution of OM among grain size fractions. We propose a conceptual model to account for this dimensionality in 14C variability that invokes two predominant modes of OM preservation within different grain size fractions of Arabian Sea sediment: finer (63 µm) fractions includes materials encapsulated within microfossils and/or entrained fossil (14C-depleted) OC hosted in detrital mineral grains. Our findings highlight the value of RPO for assessment of 14C age variability in sedimentary OC, and for assessing mechanisms of OM preservation in aquatic sediments.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 15
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    Online 13C and 14C Gas Measurements by EA-IRMS–AMS at ETH Zürich (2016)
    Cambridge University Press
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    Publication Date: 2016-10-17
    Description: Studies using carbon isotopes to understand the global carbon cycle are critical to identify and quantify sources, sinks, and processes and how humans may impact them. 13C and 14C are routinely measured individually; however, there is a need to develop instrumentation that can perform concurrent online analyses that can generate rich data sets conveniently and efficiently. To satisfy these requirements, we coupled an elemental analyzer to a stable isotope mass spectrometer and an accelerator mass spectrometer system fitted with a gas ion source. We first tested the system with standard materials and then reanalyzed a sediment core from the Bay of Bengal that had been analyzed for 14C by conventional methods. The system was able to produce %C, 13C, and 14C data that were accurate and precise, and suitable for the purposes of our biogeochemistry group. The system was compact and convenient and is appropriate for use in a range of fields of research.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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  • 16
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    Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic : 14C characteristics of sedimentary carbon components and their environmental controls (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 1855–1873, doi:10.1002/2015GB005204.
    Description: Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14C measurements, including novel analyses of suberin- and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C24,26,28), plant wax FAs (C24,26,28), and n-alkanes (C27,29,31), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these “old” terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C16,18) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in 14C, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular 14C analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw.
    Description: Chinese National Key Development Program for Basic Research Grant Numbers: 2014CB954003, 2015CB954201; Knut and Alice Wallenberg Foundation; Headquarters of the Russian Academy of Sciences; Swedish Research Council; US National Oceanic and Atmospheric Administration; Russian Foundation of Basic Research Grant Numbers: (13-05-12028, 13-05-12041; Swedish Polar Research Secretariat; Nordic Council of Ministers; Government of the Russian Federation Grant Number: 2013-220-04-157; Swiss National Science foundation. Grant Number: (200021_140850 US National Science Foundation (NSF) Grant Numbers: OCE-9907129, OCE-0137005, OCE-0526268; Stanley Watson Chair for Excellence in Oceanography Grant Number: 825.10.022; ETH Zürich; NWO Rubicon; Veni Grant Number: 863.12.004; UK NERC Grant Number: NE/I024798/1; NSF. Grant Numbers: 0436118, 0732555, 1107774
    Description: 2016-05-02
    Keywords: Compound-specific radiocarbon analysis ; Terrestrial carbon markers ; Pan-arctic rivers ; Diacids ; Lignin ; Plant wax lipids
    Repository Name: Woods Hole Open Access Server
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  • 17
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    Biological and physical controls on the flux and characteristics of sinking particles on the Northwest Atlantic margin (2017)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 4539–4553, doi:10.1002/2016JC012549.
    Description: Biogenic matter characteristics and radiocarbon contents of organic carbon (OC) were examined on sinking particle samples intercepted at three nominal depths of 1000 m, 2000 m, and 3000 m (∼50 m above the seafloor) during a 3 year sediment trap program on the New England slope in the Northwest Atlantic. We have sought to characterize the sources of sinking particles in the context of vertical export of biogenic particles from the overlying water column and lateral supply of resuspended sediment particles from adjacent margin sediments. High aluminum (Al) abundances and low OC radiocarbon contents indicated contributions from resuspended sediment which was greatest at 3000 m but also significant at shallower depths. The benthic source (i.e., laterally supplied resuspended sediment) of opal appears negligible based on the absence of a correlation with Al fluxes. In comparison, CaCO3 fluxes at 3000 m showed a positive correlation with Al fluxes. Benthic sources accounted for 42 ∼ 63% of the sinking particle flux based on radiocarbon mass balance and the relationship between Al flux and CaCO3 flux. Episodic pulses of Al at 3000 m were significantly correlated with the near-bottom current at a nearby hydrographic mooring site, implying the importance of current variability in lateral particle transport. However, Al fluxes at 1000 m and 2000 m were coherent but differed from those at 3000 m, implying more than one mode of lateral supply of particles in the water column.
    Description: NSF Ocean Sciences Chemical Oceanography program Grant Numbers: OCE-0425677, OCE-0851350; Ocean and Climate Change Institute of WHOI
    Description: 2017-12-01
    Keywords: Sinking particle flux ; Biological carbon pump ; Radiocarbon ; Lateral particle supply ; Sediment resuspension ; Northwest Atlantic ; Sediment trap
    Repository Name: Woods Hole Open Access Server
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  • 18
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    Organic carbon aging during across‐shelf transport (2018)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 45 (2018): 8425-8434, doi:10.1029/2018GL078904.
    Description: Compound‐specific radiocarbon analysis was performed on different grain‐size fractions of surficial sediments to examine and compare lateral transport times (LTTs) of organic carbon. 14C aging of long‐chain leaf wax fatty acids along two dispersal pathways of fluvially derived material on adjacent continental margins implies LTTs over distances of ~30 to 500 km that range from hundreds to thousands of years. The magnitude of aging differs among grain size fractions. Our finding suggests that LTTs vary both temporally and spatially as a function of the specific properties of different continental shelf settings. Observations suggest that 14C aging is widespread during lateral transport over continental shelves, with hydrodynamic particle sorting inducing age variations among organic components residing in different grain sizes. Consideration of these phenomena is of importance for understanding carbon cycle processes and interpretation on sedimentary records on continental margins.
    Description: National Natural Science Foundation of China Grant Numbers: 41520104009, 41521064; MOE; JSPS Grant Numbers: A‐1003, 2‐1304, B‐0904, B‐0903, 22310014, 23651021, 25550020; NIES; SNSF Grant Number: 200021_140850
    Keywords: Radiocarbon ; Lateral particle transport time ; Organic carbon aging ; Continental shelf sediments ; Grain size fractions
    Repository Name: Woods Hole Open Access Server
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  • 19
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    Millennial soil retention of terrestrial organic matter deposited in the Bengal Fan (2018)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 11997, doi:10.1038/s41598-018-30091-8.
    Description: The abundance of organic carbon (OC) in vegetation and soils (~2,600 PgC) compared to carbon in the atmosphere (~830 PgC) highlights the importance of terrestrial OC in global carbon budgets. The residence time of OC in continental reservoirs, which sets the rates of carbon exchange between land and atmosphere, represents a key uncertainty in global carbon cycle dynamics. Retention of terrestrial OC can also distort bulk OC- and biomarker-based paleorecords, yet continental storage timescales remain poorly quantified. Using “bomb” radiocarbon (14C) from thermonuclear weapons testing as a tracer, we model leaf-wax fatty acid and bulk OC 14C signatures in a river-proximal marine sediment core from the Bay of Bengal in order to constrain OC storage timescales within the Ganges-Brahmaputra (G-B) watershed. Our model shows that 79–83% of the leaf-waxes in this core were stored in continental reservoirs for an average of 1,000–1,200 calendar years, while the remainder was stored for an average of 15 years. This age structure distorts high-resolution organic paleorecords across geologically rapid events, highlighting that compound-specific proxy approaches must consider storage timescales. Furthermore, these results show that future environmental change could destabilize large stores of old - yet reactive - OC currently stored in tropical basins.
    Description: We acknowledge funding support from the Agouron Institute Postdoctoral Fellowship (K.L.F), the US National Science Foundation (Awards: OCE-1333387 and OCE-13333826), the Investment in Science Fund given primarily by WHOI Trustee and Corporation Members, and the Swiss National Science Foundation (Award: 200020_163162).
    Repository Name: Woods Hole Open Access Server
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  • 20
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    Temporal and spatial variability of particle transport in the deep Arctic Canada Basin (2015)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 2784–2799, doi:10.1002/2014JC010643.
    Description: To better understand the current carbon cycle and potentially detect its change in the rapidly changing Arctic Ocean, we examined sinking particles collected quasi-continuously over a period of 7 years (2004–2011) by bottom-tethered sediment trap moorings in the central Canada Basin. Total mass flux was very low (〈100 mg m−2 d−1) at all sites and was temporally decoupled from the cycle of primary production in surface waters. Extremely low radiocarbon contents of particulate organic carbon and high aluminum contents in sinking particles reveal high contributions of resuspended sediment to total sinking particle flux in the deep Canada Basin. Station A (75°N, 150°W) in the southwest quadrant of the Canada Basin is most strongly influenced while Station C (77°N, 140°W) in the northeast quadrant is least influenced by lateral particle supply based on radiocarbon content and Al concentration. The results at Station A, where three sediment traps were deployed at different depths, imply that the most likely mode of lateral particle transport was as thick clouds of enhanced particle concentration extending well above the seafloor. At present, only 1%–2% of the low levels of new production in Canada Basin surface waters reaches the interior basin. Lateral POC supply therefore appears to be the major source of organic matter to the interior basin. However, ongoing changes to surface ocean boundary conditions may influence both lateral and vertical supply of particulate material to the deep Canada Basin.
    Description: This research was funded by the NSF Division of Polar Programs (ARC-0909377), the Ocean and Climate Change Institute of Woods Hole Oceanographic Institution, and ETH Zürich. J.H. and M.K. were partly supported by the National Research Foundation of Korea grant funded by the Korean Government (2011–0013629).
    Keywords: Canada Basin ; Particulate organic carbon ; Lateral supply ; Radiocarbon ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
    Type: Article
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