Jennings Joe C.

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Joe C.

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  • Technical Report
    A trans-Indian Ocean hydrographic section at latitude 32°South : data report of RRS Charles Darwin cruise #29
    (Woods Hole Oceanographic Institution, 1992-01) Cook, Margaret F. ; Toole, John M. ; Knapp, George P. ; Fine, Rana A. ; Top, Zafer ; Jennings, Joe C.
    A trans-Indian Ocean hydrographic section employing CTD/O2 profilers was conducted between Africa and Australia during austral spring 1987. The cruise track ranged between 29°S and 34°S; the average latitude of the crossing was 32°S. The purpose of the cruise was to explore various aspects of the South Indian Ocean including the characteristics of the core water masses of this ocean, the strength of the subtropical gyre, the structure and transport of deep western-boundary currents, and the net meridional heat flux. A total of 109 CTD/O2 profiles with associated rosette water sample measurements and 347 XBT profiles were collected, supplemented by underway upper ocean velocity, bathymetric and sea surface temperature and salinity data. This report detals the data collection, calibration, and reduction methods, and summarizes the hydrographic observations.
  • Article
    Basin-scale inputs of cobalt, iron, and manganese from the Benguela-Angola front to the South Atlantic Ocean
    (Association for the Sciences of Limnology and Oceanography, 2012-07) Noble, Abigail E. ; Lamborg, Carl H. ; Ohnemus, Daniel C. ; Lam, Phoebe J. ; Goepfert, Tyler J. ; Measures, Christopher I. ; Frame, Caitlin H. ; Casciotti, Karen L. ; DiTullio, Giacomo R. ; Jennings, Joe C. ; Saito, Mak A.
    We present full-depth zonal sections of total dissolved cobalt, iron, manganese, and labile cobalt from the South Atlantic Ocean. A basin-scale plume from the African coast appeared to be a major source of dissolved metals to this region, with high cobalt concentrations in the oxygen minimum zone of the Angola Dome and extending 2500 km into the subtropical gyre. Metal concentrations were elevated along the coastal shelf, likely due to reductive dissolution and resuspension of particulate matter. Linear relationships between cobalt, N2O, and O2, as well as low surface aluminum supported a coastal rather than atmospheric cobalt source. Lateral advection coupled with upwelling, biological uptake, and remineralization delivered these metals to the basin, as evident in two zonal transects with distinct physical processes that exhibited different metal distributions. Scavenging rates within the coastal plume differed for the three metals; iron was removed fastest, manganese removal was 2.5 times slower, and cobalt scavenging could not be discerned from water mass mixing. Because scavenging, biological utilization, and export constantly deplete the oceanic inventories of these three hybrid-type metals, point sources of the scale observed here likely serve as vital drivers of their oceanic cycles. Manganese concentrations were elevated in surface waters across the basin, likely due to coupled redox processes acting to concentrate the dissolved species there. These observations of basin-scale hybrid metal plumes combined with the recent projections of expanding oxygen minimum zones suggest a potential mechanism for effects on ocean primary production and nitrogen fixation via increases in trace metal source inputs.