A new constraint on global air-sea CO2 fluxes using bottle carbon data

Authors

  • Tristan P. Sasse,

    Corresponding author
    1. Climate Change Research Centre, Faculty of Science, University of New South Wales, Sydney, New South Wales, Australia
    • Corresponding author: T. P. Sasse, Climate Change Research Centre, Faculty of Science, University of New South Wales, Sydney, NSW 2052, Australia. (t.sasse@unsw.edu.au)

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  • Ben I. McNeil,

    1. Climate Change Research Centre, Faculty of Science, University of New South Wales, Sydney, New South Wales, Australia
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  • Gab Abramowitz

    1. Climate Change Research Centre, Faculty of Science, University of New South Wales, Sydney, New South Wales, Australia
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Abstract

[1] We develop a new observationally derived monthly ocean surface climatology for the partial pressure of CO2 (pCO2) that allows an independent data-based constraint on contemporary air-sea CO2 fluxes. Our approach uses a neural network, trained on ~17,800 bottle-derived measurements of pCO2, to diagnose monthly pCO2 levels from standard ocean hydrographic data. Although the pattern of contemporary air-sea CO2 fluxes is generally consistent with the independent underway pCO2 data network, we find a strong shift in the magnitude of oceanic sources and sinks of CO2. In particular, we find a contemporary Southern Hemisphere oceanic CO2 uptake of 0.93 PgC/year, driven by a prominent CO2 sink in the subpolar region (25°S–60°S), that is five times the magnitude of the Northern Hemisphere oceanic sink (0.18 PgC/year). Globally, our results suggest a net open-ocean CO2 sink of 1.55 ± 0.32 PgC/year for the nominal year of 2000.

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