HR: 1330h
AN: OS23A-06    [Abstracts]
TI: Space-Time Variability of the Plata Plume Inferred From Sea Spectral Reflectance Data
AU: * Piola, A R
EM: apiola@hidro.gov.ar
AF: Servicio de Hidrografˇa Naval, Av. Montes de Oca 2124. 4to Piso, Buenos Aires, C1270ABV Argentina
AU: Romero, S I
EM: dinoce@hidro.gov.ar
AF: Servicio de Hidrografˇa Naval, Av. Montes de Oca 2124. 4to Piso, Buenos Aires, C1270ABV Argentina
AB: The Plata River, discharges on average 23,000 cubic meters per second of freshwater into the western South Atlantic. The Plata diluted waters are laden with sediments and organic matter, which strongly affect the physical and bio-geo-chemical properties and the circulation over the neighboring ocean. Historical hydrographic data and numerical models show large seasonal variations in the northward and offshore extension of the river plume. Though the Plata variations induce a large impact on the coastal ecosystem, little is known about the interannual and intra-seasonal variability. The Plata plume induces a strong radiance signal in the visible band associated to the combination of productivity and suspended particles. To characterize the space-time variability of the Plata plume we use five years (1998-2002) of surface chlorophyll-a concentrations (chl-a) derived from NASA's Sea-viewing Wide-field of View Sensor. Though the data is too noisy to allow computation of surface salinity from satellite observations, comparison of in-situ surface salinities obtained during the Plata expeditions with 1 km resolution chl-a data, shows that the later can be used to clearly distinguish the Plata derived waters from open ocean waters. Salinities < 30 (> 35) are associated with log chl-a > 0.8 (< -0.4) mg/m3. Our analysis reveals northeastward plume penetrations beyond 28S during the austral winter and retractions in summer to 32S, qualitatively similar to those inferred from historical hydrographic data and numerical simulations. High chl-a (low salinity) waters advance and retract along-shore at a mean rate of about 800km/3months, similar to results from numerical simulations. Maximum along-shore plume penetrations (>1100km) are observed in winter 2002, preceded by a period of normal outflow and relatively strong southeasterly wind. In contrast the plume presented the least along-shore penetration (400 km) in winter 1999, also preceded by near average outflow but northeasterly winds north of 31S. These results suggest that sea spectral reflectance (SSR) imagery can be used to trace the variations in the extension of the Plata plume over the continental shelf.
DE: 4215 Climate and interannual variability (3309)
DE: 4219 Continental shelf processes
DE: 4223 Descriptive and regional oceanography
DE: 4275 Remote sensing and electromagnetic processes (0689)
DE: 4552 Ocean optics
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly