Towards Constraining Sources of Lithogenic Metals in the Northern Gulf of Mexico

• Main Authors: Hayes, Christopher T., Shiller, Alan M., Milroy, Scott P.
• Format: Text
• Language: unknown
• Published: The Aquila Digital Community 2022
• Subjects: Oceanography and Atmospheric Sciences and Meteorology; Physical Sciences and Mathematics; North Atlantic
• Online Access: https://aquila.usm.edu/fac_pubs/19836; https://doi-org.lynx.lib.usm.edu/10.1029/2022JC018523

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.