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A mechanistic account of increasing seasonal variations in the rate of ocean uptake of anthropogenic carbon
1Institut Universitaire Européen de la Mer (UMS3113), CNRS, centre IRD de Bretagne, Plouzané, France
2Laboratoire de Physique des Océans (UMR6523), IRD, centre IRD de Bretagne, Plouzané, France
3Atmospheric and Ocean Sciences, Princeton University, Princeton, New Jersey, USA
Abstract. A three-dimensional circulation model that includes a representation of anthropogenic carbon as a passive tracer is forced with climatological surface fluxes. This simulation is then used to compute offline the anthropogenic ΔpCO2 (defined as the difference between the atmospheric CO2 and its seawater partial pressure) trends over three decades between the years 1970 and 2000. It is shown that the mean increasing trends in ΔpCO2 reflects an increase of the seasonal amplitude of ΔpCO2. In particular, the ocean uptake of anthropogenic CO2 is decreasing (negative trends in ΔpCO2) in boreal (austral) summer in the Northern (Southern) Hemisphere in the subtropical gyres between 20° N(S) and 40° N(S). In our simulation, the increased amplitude of the seasonal trends of the ΔpCO2 is mainly explained by the seasonal sea surface temperature (SST) acting on the anthropogenic increase of the dissolved inorganic carbon (DIC). It is also shown that the seasonality of the anthropogenic DIC has very little effect on the decadal trends. This study underscores the need for surface CO2 measurements that resolve the seasonal cycle throughout much of the extratropical oceans.
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Citation: Gorgues, T., Aumont, O., and Rodgers, K. B.: A mechanistic account of increasing seasonal variations in the rate of ocean uptake of anthropogenic carbon, Biogeosciences Discuss., 7, 745-764, 2010. Bibtex EndNote Reference Manager
