HR: 1400h
AN: OS33A-09 [Abstracts]
TI: Tracing a River Plume Using Satellite Derived Surface Chlorophyll
AU: Piola, A R
EM: apiola@hidro.gov.ar
AF: Deapartamento Oceanorgafia
Servicio de Hidrografia Naval, Av. Montes de Oca 2124, Buenos Aires, C1270ABV, Argentina
AU: Piola, A R
EM: apiola@hidro.gov.ar
AF: Departamento de Ciencias de la Atmosfera y los Oceanos, FCEN, Universidad de Buenos
Aires, Intendente Guiraldes 2160
Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina
AU: * Romero, S I
EM: sromero@hidro.gov.ar
AF: Deapartamento Oceanorgafia
Servicio de Hidrografia Naval, Av. Montes de Oca 2124, Buenos Aires, C1270ABV, Argentina
AU: * Romero, S I
EM: sromero@hidro.gov.ar
AF: Departamento de Ciencias de la Atmosfera y los Oceanos, FCEN, Universidad de Buenos
Aires, Intendente Guiraldes 2160
Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina
AU: Zajaczkovski, U
EM: uriel.zaja@gmail.com
AF: Deapartamento Oceanorgafia
Servicio de Hidrografia Naval, Av. Montes de Oca 2124, Buenos Aires, C1270ABV, Argentina
AU: Zajaczkovski, U
EM: uriel.zaja@gmail.com
AF: Departamento de Ciencias de la Atmosfera y los Oceanos, FCEN, Universidad de Buenos
Aires, Intendente Guiraldes 2160
Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina
AB:
Based on the analysis of satellite derived surface chlorophyll-a (CSAT) and concomitant in-situ surface salinity (S)
data we show that CSAT estimated by the OC4v4 SeaWiFS retrieval algorithm is a good indicator of surface
salinity over a continental shelf dominated by freshwater discharge. The CSAT 'S relation is illustrated for the case
of Rio de la Plata, which discharges about 23,000 m3/s into the western South Atlantic near 35°S. During
two high resolution surveys conducted in 2003 and 2004 CSAT and concomitant S observations present high
correlations: 0.95 and 0.84, respectively. The log (CSAT) distribution over the shelf presents three modes, each
associated to distinct water masses based on their S ranges. Across the offshore edge of the Plata plume the log
(CSAT) 0.4 to 0.8 range is associated with a sharp surface salinity transition from 28.5 to 32.5. CSAT data from
the period 1998-2006 are then used to characterize the space time variability of the Plata plume from seasonal to
interannual time scales. The seasonal plume variations derived from the CSAT analysis are in excellent
agreement with S variations based on historical hydrographic data. In austral winter CSAT maxima extend
northeastward from the Plata estuary and along the southern Brazil shelf beyond 30°S, while in summer
the high CSAT waters retreat to 32°S and extend south of the estuary to about 37.5°S, only
exceeding this latitude during extraordinary events. Satellite derived winds and river outflow data are used to
assess their effects on the plume spreading over the continental shelf. The seasonal CSAT variations northeast
of the estuary are primarily controlled by reversals of the along-shore wind stress and surface currents. These
CSAT variations over the shelf are opposite to what would be expected for phytoplankton blooms associated with
wind induced coastal upwelling. At interannual time scales the Plata plume penetrations in winter range between
1200 and 650 km from the estuary, associated with changes in the intensity and persistency of the northeastward
wind stress. Intense southwestward plume extensions, beyond 38°S, are dominated by interannual time
scales and appear to be related to the magnitude of the river outflow. The plume response to the large river
outflow fluctuations observed at interannual time scales is moderate, except offshore from the estuary mouth,
where outflow variations lead CSAT variations by about two months.
DE: 0480 Remote sensing
DE: 4217 Coastal processes
DE: 4223 Descriptive and regional oceanography
DE: 4264 Ocean optics (0649)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly