A seasonal tropical sink for atmospheric
CO2 in the
Marine Chemistry, Volume 68, Issue 3,
J. F. Ternon, C. Oudot, A. Dessier and D. Diverres
Summary of
Points:
·
In
the western equatorial
·
Near
the coast of South America where the salinities are the lowest (S<20),
the fugacity of oceanic CO2 decreases down to 150 uatm and the
shelf area acts as a significant sink for atmospheric CO2.
·
The
dilution effect by low-salinity water only partly accounts for the decrease in
CO2, and the biological production in the Amazon Plume water
enriched in nutrients lowers dissolved inorganic carbon and decreases the fCO2
by nearly 30%.
·
The
low-salinity Amazon water tongue spreads northwestwards along the coast by the
North Brazil Current (NBC) and is deflected eastwards north of 5°N in the NBC retroflection in summer.
·
Consequently,
the low-salinity and oceanic fCO2 (below the atmospheric fCO2
level) signatures may extend more than 2000 km eastwards. The impact of the
river outflow on the air¯sea CO2
exchanges in the western region is demonstrated by using the climatologies of the sea surface salinity (SSS) to estimate
the magnitude of the annual net CO2 flux in the western part of the
equatorial
·
This
is in contrast with the central and eastern parts that are sources for
atmospheric CO2.
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