A Margin Source of Cd in the Western North Pacific Ocean

Peter L Morton, National High Magnetic Field Laboratory, Geochemistry, Tallahassee, FL, United States, Cheryl Zurbrick, Massachusetts Institute of Technology, Cambridge, MA, United States, William M Landing, Florida State University, Earth, Ocean, and Atmospheric Science, Tallahassee, FL, United States, Clifton S Buck, Skidaway Institute of Oceanography, Savannah, GA, United States, Celine Gallon, UCSC, Santa Cruz, CA, United States, John R Donat, Old Dominion University, Chemistry, Norfolk, VA, United States, Alan M Shiller, University of Southern Mississippi, Department of Marine Science, Stennis Space Center, MS, United States and Arthur Russell Flegal Jr, University of California Santa Cruz, Santa Cruz, CA, United States
Abstract:
To explore the influence of atmospheric deposition on the biogeochemistry of Cd in the western and central North Pacific Ocean, dissolved, total dissolved, marine particulate and soluble aerosol Cd were measured in samples collected during the 2002 Intergovernmental Oceanographic Commission (IOC-4) Global Investigation of Pollution in the Marine Environment (GIPME) cruise. Aerosols and surface waters of the Kuroshio Current and oligotrophic subtropical gyre were depleted in Cd, even during dust events, indicating that aerosol inputs of Cd are relatively inconsequential for these surface waters. Rather, vertical upward fluxes and lateral transport from the Aleutian margin produce high dissolved Cd concentrations in the surface waters of the Western Subarctic Gyre. Waters near the Aleutian Margin were subsequently enriched in Cd and produced dissolved Cd/PO4 ratios above those in deep water. This excess Cd, combined with the high nutrient/low Fe conditions of the Western Subarctic Gyre, induced high particulate Cd/P ratios in the surface waters, consistent with increased biological uptake of Cd via survival mechanisms designed to sequester Fe. Ultimately, the Cd-enriched waters of the Western Subarctic Gyre are exported laterally to the central subtropical gyre.
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