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2002 LAPCOD Meeting
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A Lagrangian Perspective of Biogeochemical Transformations in River Plumes.
Gary L Hitchcock, W. J. Wiseman, Jr., R. Chen
University of Miami
ghitchcock@rsmas.miami.edu(Abstract received 11/11/2002 for session A)
ABSTRACT
River plumes are highly dynamic environments in which terrestrial materials are discharged to the coastal ocean. Large rivers, such as the Amazon, Orinoco, and Mississippi, deliver significant quantities of dissolved inorganic nutrients and terrestrial organic matter to the coastal zone. Transformations of these materials directly influence the magnitude of coastal productivity and influence the photic environment. The shallow depth of many river plumes, in combination with their rapid response to forcing by winds and currents, complicate studies of transformations of dissolved and particulate matter in these dynamic environments. Lagrangian studies of property distributions in river plumes provide one means of identifying processes that regulate the distribution of dissolved inorganic nutrients and Chromophoric Dissolved Organic Matter (CDOM). We have conducted a series of observations in the Mississippi River plume in which the spatial distribution of nutrients and CDOM were mapped while following surface drifters. In all cases, concentrations of dissolved materials in the river plume decrease in a quasi-linear manner with time. These observations argue for physical dilution as a primary mechanism controlling the initial distribution of dissolved materials in this plume. Convergent surface fronts at the edge of the plume appear to be the primary site where biological and other biogeochemical processes transform dissolved and particulate matter as river waters are mixed with ambient shelf water.
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2002 LAPCOD Meeting, Key Largo, Florida, December 12-16, 2000