Monitoring the biophysical properties along Lagrangian advection pathways in the Amazon River plume

Severine Fournier1, Lucile Gaultier2, Douglas C Vandemark3, Joseph Salisbury II4, Tong Lee5 and Michelle Gierach5, (1)JPL/NASA/Caltech, Pasadena, CA, United States, (2)Jet Propulsion Laboratory, Pasadena, CA, United States, (3)University of New Hampshire Main Campus, Durham, NH, United States, (4)University of New Hampshire, Durham, NH, United States, (5)NASA Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
Large rivers are important to marine biogeochemistry and air-sea interactions. The freshwater inputs associated with major river plumes modify the local and regional sea surface salinity (SSS) and in the mean time carry a large amount of organic and inorganic particulates into the ocean. Monitoring of the spatial and temporal variability of river plumes extension is therefore important to the physics and biophysical interaction at regional scales.

With the launches of the NASA Aquarius/Sac-D missions and the ESA Soil Moisture and Ocean Salinity (SMOS), we are now able to use the low-resolution SSS observations in combination with altimetry and high-resolution ocean color observations to monitor the physical and biogeochemical properties of river plumes.

Our study focuses on the Amazon River, the world’s largest river in terms of discharge. Waters from the Amazon River are carried northwestward across the equator along the Brazilian shelf by the North Brazilian Current (NBC) and eastward along the North Equatorial Counter Current. Large oceanic rings shed off the NBC retroflection near 8∘N in the North Tropical Atlantic Ocean. Large-scale gradients of SSS, colored detrital matter (cdm) and sea surface temperature (SST) associated with these rings are visible from space using SSS, SST and ocean color sensors. These rings carry freshwaters highly concentrated in organic and inorganic matter towards the Caribbean Sea and offshore.

In this study, we use a Lagrangian advection method to track the particles from the Amazon mouth to the open ocean and follow their biophysical properties along their trajectories using measurements from Aquarius, SMOS, and Aqua MODIS. The pathways of the Amazon plume waters can therefore be analyzed, enabling an investigation of the physical and biogeochemical processes associated with the Amazon River freshwaters as they are advected and mixed from the river mouth to the open ocean.

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