The contrasting biogeochemistry of iron and manganese in the Pacific Ocean |
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| Institution: | 1. Bigelow Laboratory for Ocean Sciences, PO Box 380, 60 Bigelow Dr., East Boothbay, ME 04544, United States;2. Florida State University, Department of Earth, Ocean, and Atmospheric Science, Tallahassee, FL, United States;3. Advanced Photon Source, Argonne National Laboratory, Argonne, IL, United States;1. NIOZ Royal Netherland Institute for Sea Research, Department of Ocean Systems, PO Box 59, 1790 AB Den Burg, the Netherlands;2. College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA;3. Korea Polar Research Institute, 26, Songdomirae-ro, Yeonsu-gu, Incheon 21990, Republic of Korea;4. Faculty of Geosciences, Utrecht University, 3584 CB Utrecht, the Netherlands;5. Centre for Isotope Research – Oceans, University of Groningen, PO Box 72, 9700 AB Groningen, the Netherlands;1. School of Ocean and Earth Science and Technology, University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, HI 96822, USA;2. Rosenstiel School for Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA;3. MIT/WHOI Joint Program in Chemical Oceanography, MIT E25-615, 45 Carleton St., Cambridge, MA 02142, USA;4. Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529, USA;5. Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA;1. Department of Oceanography, Texas A&M University, College Station, TX 77840, USA;2. National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA;3. Bigelow Laboratory for Ocean Sciences, 60 Bigelow Drive, East Boothbay, ME 04544, USA;4. Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA;5. Escuela de Ciencias del Mar, Facultad de Ciencias del Mar y Geograf?a , Pontifica Universidad Cato?ica de Valparaiso, Valparaiso, Chile;6. InstitutoMilenio de Oceanografia, Casilla 1313, Concepcion, Chile;7. Department of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, HI 96822, USA;8. Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA;9. School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China;10. Lamont-Doherty Earth Observatory of Columbia University, Post Office Box 1000, Palisades, NY 10964, USA;11. Department of Marine and Coastal Sciences and Department of Earth and Planetary Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901, USA;1. Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA;2. Lamont Doherty Earth Observatory, Palisades, NY 10964, USA;3. Massachusetts Institute of Technology, Cambridge, MA 02139, USA;4. Old Dominion University, Norfolk, VA 23529, USA |
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| Abstract: | Vertical and horizontal distributions of dissolved and suspended particulate Fe and Mn, and vertical fluxes of these metals (obtained with sediment traps) were determined throughout the Pacific Ocean. In general, dissolved Fe is low in surface and deep waters (0.1 to 0.7 nmol/kg), with maxima associated with the intermediate depth oxygen minimum zone (2.0 to 6.6 nmol/kg). Vertical distributions of dissolved Mn are similar to previous reports, exhibiting a surface maximum, a subsurface minimum, a Mn maximum layer coincident with the oxygen minimum zone, and lowest values in deep waters.Near-shore removal processes are more intense for dissolved Fe than for dissolved Mn. Dissolved Mn in the surface mixed layer remains elevated much farther offshore than dissolved Fe. Elevated near-surface dissolved Mn concentrations occur in the North Pacific Equatorial Current, suggesting transport from the eastern boundary. Near-surface mixed-layer dissolved Mn concentrations are higher in the North Pacific gyre reflecting enhanced northern hemisphere aeolian sources.Residence time estimates for the settling of refractory paniculate Fe and Mn from the upper water column are 62–220 days (Fe), and 105–235 days (Mn). In contrast, residence times for the scavenging of dissolved Fe and Mn are 2–13 years (Fe) and 3–74 years (Mn). Scavenging residence times for dissolved Mn based on horizontal mixing in the surface mixed layer of the northeast Pacific are 0.4 years (nearshore) to 19 years (1000 km offshore).There is no evidence for in situ Fe redox dissolution within sub-oxic waters in the eastern tropical North Pacific. Dissolved Fe appeared to be controlled by dissolution from sub-oxic sediments, with oxidative scavenging in the water column or upper sediment layers. However, in situ Mn dissolution within the oxygen minimum zone was evident. |
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