Particulate matter in the south Atlantic Ocean

• Main Author: Wood, Megan Maria
• Format: Thesis
• Language: English
• Published: Texas A&M University 1993
• Subjects: geology; Major geology; Antarctic; The Antarctic; Austral; Argentine; Antarc*; South Atlantic Ocean
• Online Access: http://hdl.handle.net/1969.1/ETD-TAMU-1993-THESIS-W877

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [e-mail], referencing the URI of the item. Includes bibliographical references. The particulate matter (PM) distribution in the south Atlantic Ocean and its relationship to water masses and currents were determined from optical and hydrographic data. Attenuation coefficients were obtained by interfacing a beam transmissometer with a CTD during hydrographic surveys on Legs 4-6 of the South Atlantic Ventilation Experiment (SAVE) from December 1988 to April 1989, during the austral summer and autumn. Beam attenuation due to particles (c p ) was determined and found to be maximal at or near the surface, decreasing rapidly in the upper 100-200 m, and more gradually below that depth. The highest surface values are in the Argentine Basin, where c p consistently exceeds 0.2 m-1 (approximately 104 ug/1).In the Argentine and Cape Basins, c p increases near the seafloor, indicating the presence of a nepheloid layer. In the Argentine Basin, the nepheloid layer is intense and widespread. Maximum c p there reaches 1.175 m-1 (approximately 1750 ug/1). The Brazil Basin has the lowest concentrations at all depths. The nepheloid layers are caused by advection and resuspension of PM by Antarctic Bottom Water (AABW). AABW entrains significant amounts of sediment, both before it enters the South Atlantic and as it moves through the Argentine Basin, particularly along the southern and western margins of the basin. Resuspension of previously- deposited PM is caused by high AABW velocities and is correlated with areas of high surface eddy kinetic energy. PM is not a conservative tracer of water masses or currents. Although the Falkland and Benguela Currents can be traced on sections of beam attenuation, the Brazil Current, the Antarctic Circumpolar Current, and the Southern Equatorial Current cannot. While beam attenuation data are not useful as a tracer of water masses, they are excellent indicators of the location and intensity of local biologic productivity as well as local physical processes such as resuspension and advection.