Modern Dust Deposition and Dissolved Iron Residence Times in the Eastern Tropical Pacific Ocean

Sebastian M Vivancos1,2, Robert F Anderson1,3, Frank J Pavia2,4, Martin Q Fleisher1, Yanbin Lu5, Pu Zhang6, Hai Cheng7,8 and R. Lawrence Edwards9, (1)Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, United States, (2)Department of Earth and Environmental Sciences, Columbia University, New York, NY, United States, (3)Department of Earth and Environmental Sciences, Columbia University, New York, United States, (4)Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, United States, (5)University of Minnesota, Department of Earth Sciences, Minneapolis, MN, United States, (6)Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an, China, (7)University of Minnesota, Department of Earth and Environmental Sciences, Minneapolis, United States, (8)Xi'an Jiaotong University, Institute of Global Environmental Change, Xian, China, (9)Department of Earth Sciences, University of Minnesota, Minneapolis, MN, United States
Abstract:
We use dissolved 230Th and 232Th data along the U.S. GEOTRACES Equatorial Pacific Zonal Transect (EPZT) from Peru to Tahiti to quantify dust input to the region. Dust in the global oceans is a mineral ballast that helps carry organic matter to depth, a reactive particle surface that scavenges trace metals such as Th and Pa from the water column, and through its dissolution dust provides essential micronutrients, such as iron, that stimulate productivity. When integrating Th inventories from the sea surface to 500 meters water depth (Hayes et al., Earth Planet. Sci. Lett., 383 (2013) 16-25), we find that dust fluxes along the EPZT are an order of magnitude lower (0.18-1.61 g/m2/yr) than along the U.S. GEOTRACES Atlantic Transect (Mauritania to Bermuda; 3.22 to 10.56 g/m2/yr). Dust fluxes decrease with distance away from the dust source (i.e., the continents). Using an Fe/Th ratio of 2660 g/g for dust and assuming a Fe/Th solubility ratio of 1.0 (Hayes et al., Geochim. Cosmochim. Acta, 169 (2015) 1-16), we calculate a dissolved iron flux of 12.06 to 109.88 µmol/m2/yr to the EPZT region. Utilizing dissolved iron data along the EPZT (Resing et al., Nature, 523 (2015) 200-203), we calculate a dissolved iron residence time integrated from the sea surface to 500 meters water depth of 4 to 11 years.
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