Lead and Lead Isotope Sample Collection and Analysis for the U.S. GEOTRACES Zonal North Atlantic Survey Section

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The international GEOTRACES program has been developed to produce a global framework of key trace elements and isotopes that will describe the contemporary distributions of these properties in the ocean. This information can then be used to constrain models of the processes and fluxes of biogeochemically important elements and key tracers that frame flux processes and transformations. A scientist from Massachusetts Institute of Technology will collect samples during the GEOTRACES North Atlantic cruise in 2010 and analyze them for lead (Pb) and Pb isotopes. Samples will be taken from sites that exhibit the physical and biogeochemical processes that influence trace metals and their isotopes (i.e., strong meridional advection, boundary scavenging and sources, aeolian deposition, input of intermediate waters from the Mediterranean and Labrador Seas, and evidence of anthropogenic impacts). Amongst the questions the scientist will address with the dataset to be generated are the following: (1) have profiles of Pb and Pb isotopes in the ocean evolved in the western and eastern subtropical Atlantic since 1999; (2) is their distribution consistent with advective transport or with exchange on sinking particle; (3) are Pb or Pb isotope signals from hydrothermal vents transported a significant distance beyond the source?; and (4) how do upper and lower North Atlantic Deep Water differ in their Pb and Pb isotopic composition, and how are these differences expressed laterally over the western boundary? In addition, because Pb behaves similarly to other trace metals as regards atmospheric deposition, biological uptake, and abiotic scavenging, results from this study will be applicable to other elements. As regards broader impacts, this work will aid in creating more accurate biogeochemical models allowing scientists to access the impact of future climate change and anthropogenic pollution. One graduate student would be trained and supported as part of this project.