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Prevalence of strong vertical CO2 and O2 variability in the top meters of the ocean

September 19, 2013

 The gradient in the partial pressure of carbon dioxide (pCO2) across the air-sea boundary layer is the main driving force for the air-sea CO2 flux. Global data bases for surface seawater pCO2 are actually based on pCO2 measurements from several meters below the sea surface, assuming a homogeneous distribution between the diffusive boundary layer and the upper top meters of the ocean. Compiling vertical profiles of pCO2, temperature, and dissolved oxygen in the upper 5–8 m of the ocean from different biogeographical areas, we detected a mean difference between the boundary layer and 5 m pCO2 of 13 ± 1 µatm. Temperature gradients accounted for only 11% of this pCO2 gradient in the top meters of the ocean; thus, pointing to a heterogeneous biological activity underneath the air-sea boundary layer as the main factor controlling the top meters pCO2 variability. Observations of pCO2 just beneath the air-sea boundary layer should be further investigated in order to estimate possible biases in calculating global air-sea CO2 fluxes.

Calleja M Ll, Duarte C M, Álvarez M, Vaquer-Sunyer R, Agustí S, Herndl G J, in press. Prevalence of strong vertical CO2 and O2 variability in the top meters of the ocean, Global Biogeochemical Cycles, 2013, doi:10.1002/gbc.20081. Article.

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