9311500 FALKNER The largest and most precise data base for any trace element in the oceans is that of barium whose concentrations were measured on the global scale as part of the GEOSECS program in the 1970's. From that effort, it was confirmed that Ba undergoes nutrient-like cycling in the oceans and that it behaves more like the constituents of the hard parts of organisms (i.e. Si and alkalinity) than those of their tissues (i.e. P and N). Work on particulate matter has shown that the principal phase responsible for the transport of Ba is the mineral barite (BaSO4), which is somehow precipitated in micro environments provided by decaying organisms and tends to accumulate in the sediments underlying zones of high productivity. This simple understanding of Ba cycling has paved the way for its development as a probe for a variety of important oceanic processes. For example, paleo-Ba distributions, as recorded in the calcite lattices of foraminifera tests. are being reconstructed as a constraint on changes in oceanic circulation through glacial/interglacial transitions. Barium to Ca ratios in annually banding corals at select locations have been proposed to monitor changes in upwelling conditions associated with El Nino events. Sedimentary Ba is thought to serve as an index of paleo-productivity in overlying surface waters and on a more immediate time-scale, suspended particulate barite in the water column has been suggested to provide a measure of the net rate of carbon export from the euphotic zone. While considerable strides in the development of Ba as an investigative tool have been made, realization of its full potential requires a more thorough understanding of its behavior in the modern ocean. This study will contribute dissolved Ba analyses to resolve outstanding issues regarding Ba cycling in the oceans. In addition, the data generated will be used in Indian and Antarctic Ocean modeling studies being conducted in collaboration with French and Belgian colleagues.
