Influence of the Amazon River Runoff on the Tropical Atlantic

Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere, Volume 26, Issue 2, 2001, Pages 137-142
S. Masson and P Delecluse



Summary of Points:

        The Amazon has the biggest flow in the world, 0.2 Sv (1 Sv = 106 m3/s), and is responsible for a large part of the low Sea Surface Salinity (SSS) in the west tropical Atlantic ocean.

        Comparison of simulations with constant or monthly runoffs shows that the spread of the Amazon fresh waters offshore of the north Brazilian coast is controlled by the ocean circulation and not by the Amazon flow.

        In the model like on the observations, SSS minimum is observed in summer three months after the Amazon flood.

        A thick (more than 40 m) Barrier Layer (BL) is present every summer north of the Amazon mouth.

        Because of the strong and shallow salinity gradient associated with the Amazon freshwater, an important part of the solar radiation is trapped in the BL and creates an inversion of the vertical gradient of temperature. Freshwater flux is also able to bend the sea surface. The geostrophic part of the North Brazilian Current (NBC) retroflection is then lightly weaker in presence of the Amazon runoff.


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