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Publication - Professor Andy Ridgwell

    Sensitivity of atmospheric CO2 to regional variability in particulate organic matter remineralization depths

    Citation

    Wilson, J, Barker, S, Edwards, N, Holden, PB & Ridgwell, A, 2018, ‘Sensitivity of atmospheric CO2 to regional variability in particulate organic matter remineralization depths’. Biogeosciences Discussions.

    Abstract

    The concentration of CO2 in the atmosphere is sensitive to
    changes in the depth at which sinking particulate organic matter is
    remineralised: often described as a change in the exponent "b" of
    the Martin curve. Sediment trap observations from deep and intermediate
    depths suggest there is a spatially heterogeneous pattern of b,
    particularly varying with latitude, but disagree over the exact spatial
    patterns. Here we use a biogeochemical model of the phosphorus cycle
    coupled with a steady-state representation of ocean circulation to
    explore the sensitivity of preformed phosphate and atmospheric CO2
    to spatial variability in remineralisation depths. A Latin hypercube
    sampling method is used to simultaneously vary the Martin curve
    indepedently within 15 different regions, as a basis for a
    regression-based analysis used to derive a quantitative measure of
    sensitivity. Approximately 30% of the sensitivity of atmospheric CO2 to changes in remineralisation depths is driven by changes in the Subantarctic region (36°S to 60°S),
    simliar in magnitude to the Pacific basin despite the much smaller area
    and lower productivity. Overall, the absolute magnitude of sensitivity
    is controlled by export production but the relative spatial patterns in
    sensitivity are predominantly constrained by ocean circulation pathways.
    The high sensitivity in the Subantarctic regions is driven by a
    combination of high export production and the high connectivity of these
    regions to regions important for the export of preformed nutrients such
    as the Southern Ocean and North Atlantic. Overall, regionally varying
    remineralisation depths contribute to variability in CO2 of
    between ±5–15 ppm relative to a global mean change in remineralisation
    depth. Future changes in the environmental and ecological drivers of
    remineralisation, such as temperature and ocean acidification, are
    expected to be most significant in the high latitudes where CO2
    sensitivity to remineralisation is also highest. The importance of
    ocean circulation pathways to the high sensitivity in Subantarctic
    regions also has significance for past climates given the importance of
    circulation changes in the Southern Ocean.

    Full details in the University publications repository