Geophysical Research Letters

Insights into particle formation and remineralization using the short-lived radionuclide, Thoruim-234

Authors

  • Kanchan Maiti,

    1. Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
    2. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
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  • Claudia R. Benitez-Nelson,

    1. Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina, USA
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  • Ken O. Buesseler

    1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
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Abstract

[1] Simple mass balance models are applied to a high resolution 234Th profile from the northwest Pacific to examine the magnitude, rate, and depth distribution of particle remineralization processes below the euphotic zone (Ez). Here, excess 234Th (234Th > 238U) below the Ez is attributed to fragmentation processes that result in the conversion of sinking to non-sinking particles. By considering particulate organic carbon (POC) to 234Th ratios on particles, we show that POC flux attenuation is larger than for 234Th, which we attribute to bacterial and zooplankton consumption of sinking POC. Three case studies are used to demonstrate how different combinations of particle fragmentation and POC respiration impact flux attenuation below the Ez. When sampled with high vertical resolution and precision, 234Th and POC/234Th ratios provide insights into both export from the Ez and the extent to which sinking particle fluxes and associated minerals are attenuated with depth.

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