Variability of Pb, Isotopes Pb and Fe in the Tropical and Subtropical Atlantic and Pacific Oceans

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ABSTRACTOCE-0002273 Near the surface, Pb and Fe show a seasonal cycle related to the development of the seasonal thermocline and seasonal input cycles, and short-term variability related to the atmospheric transport, ocean eddies, and biological blooms. In addition, anthropogenic Pb is entering the thermocline and deep ocean as a time-dependent transient tracer. The temporal evolution of Pb isotopes ratios may provide an age tracer of Northern Source deep water masses in the deep sea of particular utility in portions of the deep South Atlantic, where tritium and CFCs have not yet penetrated. For this reason, the PI will continue collecting samples on a weekly basis using the Moored In-Situ Trace Element Serial Sampler (MITESS, time series and deep seawater samples) and the Automated Trace Element sampler (ATE, samples up to 10 m depths). Results from these sampling efforts will establish monthly means and examine the causes of observed variability for Pb and Fe at Bermuda and Hawaii, as well as determine whether iron pulses are responsible for unexplained blooms at the eastern North Pacific Ocean Station "P". In addition, the PI will collect samples along the flow path of the North Atlantic Deep Water (NADW) to document the penetration of anthropogenic Pb into the south Atlantic via the NADW, assess whether Pb isotopes can be used as an age-dependent source tracer and establish the partitioning of Fe into dissolved, colloidal and particulate forms.