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Towards Constraining Sources of Lithogenic Metals in the Northern Gulf of Mexico
  • Christopher T. Hayes,
  • Alan M. Shiller,
  • Scott Milroy
Christopher T. Hayes
University of Southern Mississippi, University of Southern Mississippi

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Alan M. Shiller
University of Southern Mississippi, University of Southern Mississippi
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Scott Milroy
University of Southern Mississippi, University of Southern Mississippi
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Abstract

North African dust is known to be deposited in the Gulf of Mexico, but its deposition rate and associated supply of lithogenic dissolved metals, such as the abiotic metal thorium or the micronutrient metal iron, have not been well-quantified. 232Th is an isotope with similar sources as iron and its input can be quantified using radiogenic 230Th. By comparing dissolved 232Th fluxes at three sites in the northern Gulf of Mexico with upwind sites in the North Atlantic, we place an upper bound on North African dust contributions to 232Th and Fe in the Gulf of Mexico, which is about 30% of the total input. Precision on this bound is hindered by uncertainty in the relative rates of dust deposition in the North Atlantic and the northern Gulf of Mexico. Based on available radium data, shelf sources, including rivers, submarine groundwater discharge and benthic sedimentary releases are likely as important if not more important than dust in the budget of lithogenic metals in the Gulf of Mexico. In other words, it is likely there is no one dominant source of Th and Fe in the Gulf of Mexico. Finally, our estimated Fe input in the northern Gulf of Mexico implies an Fe residence time of less than 6 months, similar to that in the North Atlantic despite significantly higher supply rates in the Gulf of Mexico.
Apr 2022Published in Journal of Geophysical Research: Oceans volume 127 issue 4. 10.1029/2022JC018523