Nd and Sr Isotope Tracers of Deep and Shallow Ocean Circulation around South Africa

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ABSTRACTOCE-0526884Two researchers from Lamont-Doherty Earth Observatory will refine and test the utility of neodymium (Nd) isotopes as conservative tracers of water masses, as well as refine the application of the authigenic Fe-Mn-hosted Nd as an archive of the water mass signal and further explore the utility of isotopic signatures of terrigenous detritus as current tracers. Cores, water column samples, and water-borne particulates recovered off the southeast coast of South Africa from a large depth range will be used. Using isotopic and chemical analyses, the following tasks will be carried out: (1) trace Nd isotope ratios of major water masses in an important interocean exchange zone; (2) determine the effects of particle exchange on seawater Nd isotopes along a continental margin; (3) compare Nd isotopes of coretop Fe-Mn leachates to the water masses that bathe the cores: (4) determine if leachates that "fail" the "seawater integrity tests" contain a chemical signature that signals failure; and (5) calibrate the Nd and strontium isotopic signature of Agulhas water column particulates with terrigenous detritus on the seafloor in the context of existing data showing an Agulhas Current signal in South Atlantic sediments. The goal is to calibrate a series of promising circulation tracers that have many future applications in ocean circulation and paleocirculation studies. In terms of broader impacts, availability of calibrated circulation tracers will provide a means of assessing the ocean's role in climate change. It is anticipated that data obtained will be deposited into on-line databases such as SedDB (Integrated Data management for Sediment Geochemistry) and/or CHRONOS (an interactive network of federated data and tools for sedimentary geology and paleobiology), as well as a World Data Center such as NOAA's National Geophysical Data Center. As regards outreach efforts, the PIs plan to continue their participation in the Lamont Open House, wherein they discuss their research with the public. One graduate student will be trained and supported.