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Global Biogeochemical Cycles

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

Authors

  • Maria Ll. Calleja,

    Corresponding author
    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, CSIC-UIB, Esporles, Spain
    2. Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Armilla, Spain
    • Corresponding author: M. Ll. Calleja, Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Avda. de las Palmeras 4, 18100 Armilla, Granada, Spain. (marialluch.calleja@gmail.com)

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  • Carlos M. Duarte,

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, CSIC-UIB, Esporles, Spain
    2. The UWA Oceans Institute, University of Western Australia, Crawley, Western Australia, Australia
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  • Marta Álvarez,

    1. Instituto Español de Oceanografía, Centro de A Coruña, Coruña, Spain
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  • Raquel Vaquer-Sunyer,

    1. Department of Geology, Lund University, Lund, Sweden
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  • Susana Agustí,

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, CSIC-UIB, Esporles, Spain
    2. The UWA Oceans Institute, University of Western Australia, Crawley, Western Australia, Australia
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  • Gerhard J. Herndl

    1. Department of Marine Biology, University of Vienna, Vienna, Austria
    2. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, Den Burg, Netherlands
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Abstract

[1] 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.

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