Amazon River propagation evidenced by a CO2 decrease at 8°N, 38°W in September 2013

Type Article
Date 2020-11
Language English
Author(s) Lefèvre Nathalie1, Tyaquiçã Pedro1, Veleda Doris2, Perruche Coralie3, Van Gennip Simon Jan3
Affiliation(s) 1 : LOCEAN, Sorbonne Université (Université P. et M. Curie-IRD-CNRS-MNHN), Paris, France
2 : Department of Oceanography, DOCEAN, Federal University of Pernambuco (UFPE), Recife, Brazil
3 : Mercator-Ocean, Ramonville, Saint-Agne, Haute Garonne, France
Source Journal Of Marine Systems (0924-7963) (Elsevier BV), 2020-11 , Vol. 211 , P. 103419 (11p.)
DOI 10.1016/j.jmarsys.2020.103419
Keyword(s) Fugacity of CO2, Air-sea flux of CO2, Western tropical Atlantic, Amazon plume
Abstract

The surface fugacity of CO2 (fCO2) has been measured hourly at a mooring at 8°N, 38°W, using a spectrophotometric CO2 sensor, from June to October 2013. In September 2013, the fCO2 and the sea surface salinity (SSS) decrease significantly. The high precipitation due to the presence of the Intertropical Convergence Zone (ITCZ) and the propagation of low salinity waters from the Amazon River plume explain the decrease of SSS. Indeed, in fall, the retroflection of the North Brazil Current (NBC) feeds the North Equatorial Counter Current (NECC) and transports Amazon waters to the eastern part of the tropical Atlantic. Simulations from a three dimensional physical and biogeochemical model and observations at the mooring show that the Amazon plume reached the mooring in September 2013. The decrease of fCO2 is associated with a moderate peak of chlorophyll. Over the period of the CO2 observations, the site is a source of CO2 to the atmosphere of 0.65 ± 0.47 mmol m−2 day−1. Although the wind speed is at its lowest intensity in September 2013, the flux over the whole period would be about 14% higher without this month. Every month of September from 2006 to 2017, the model simulates a decrease of dissolved inorganic carbon corresponding to the SSS minimum.

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