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    An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of 234Th as a POC flux proxy

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    FATE Buesseler et al C_Th ratio revised all parts.pdf (625.9Kb)
    Date
    2005-06-18
    Author
    Buesseler, Ken O.  Concept link
    Benitez-Nelson, Claudia R.  Concept link
    Burd, Adrian B.  Concept link
    Charette, Matthew A.  Concept link
    Cochran, J. Kirk  Concept link
    Coppola, L.  Concept link
    Fisher, Nicholas S.  Concept link
    Fowler, Scott W.  Concept link
    Gardner, Wilford D.  Concept link
    Guo, L. D.  Concept link
    Gustafsson, Orjan  Concept link
    Lamborg, Carl H.  Concept link
    Masqué, Pere  Concept link
    Miquel, Juan Carlos  Concept link
    Passow, Uta  Concept link
    Santschi, Peter H.  Concept link
    Savoye, Nicolas  Concept link
    Stewart, G.  Concept link
    Trull, Thomas W.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/1206
    As published
    https://doi.org/10.1016/j.marchem.2005.10.013
    Abstract
    Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the 234Th activity distribution (in order to calculate 234Th fluxes) and an estimate of the C/234Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C/234Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C/234Th either increases or is relatively invariant with increasing particle size (size classes >1 to 100’s μm). Observations also suggest that C/234Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from 234Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2-3). We recommend sampling for C/234Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple 234Th profiles and C/234Th samples during the course of longer observation periods to better sample temporal variations in both 234Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column.
    Description
    Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 100 (2006): 213-233, doi:10.1016/j.marchem.2005.10.013.
    Collections
    • Marine Chemistry and Geochemistry (MC&G)
    Suggested Citation
    Preprint: Buesseler, Ken O., Benitez-Nelson, Claudia R., Burd, Adrian B., Charette, Matthew A., Cochran, J. Kirk, Coppola, L., Fisher, Nicholas S., Fowler, Scott W., Gardner, Wilford D., Guo, L. D., Gustafsson, Orjan, Lamborg, Carl H., Masqué, Pere, Miquel, Juan Carlos, Passow, Uta, Santschi, Peter H., Savoye, Nicolas, Stewart, G., Trull, Thomas W., "An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of 234Th as a POC flux proxy", 2005-06-18, https://doi.org/10.1016/j.marchem.2005.10.013, https://hdl.handle.net/1912/1206
     
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