Technical Comments

Comment on "Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change"

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Science  01 Feb 2008:
Vol. 319, Issue 5863, pp. 570
DOI: 10.1126/science.1146886


  • Fig. 1.

    Modeled effect of poleward intensifying winds on zonally integrated air-sea CO2 flux in the Southern Ocean over the time period 1900 to 2100. (A) Flux of natural CO2, (B) flux of total CO2, and (C) CO2 fluxes integrated over the Southern Ocean (90°S to 40°S). The smoothed curves are polynomial fits to the modeled fluxes. The nested plot in (C) displays the polynomial fits for 1900 to 2000. Negative fluxes indicate ocean outgassing. The flux of natural CO2 (A) is obtained as the difference between a control simulation with all forcings held at 1800 levels and a simulation with atmospheric CO2 fixed at 1800 levels and Southern Hemisphere winds evolving according to the Inter-governmental Panel on Climate Change AR4 model-ensemble mean, which projects a 25% strengthening and a 3.5° poleward shift of the maximum annual mean zonal wind stress by 2100 (4). The flux of total carbon is calculated as the difference between a simulation with CO2 emissions following historical estimates for the period 1800 to 1990 and the Special Report on Emissions Scenarios A2 scenario thereafter (with wind forcing held constant at 1800 levels) and a simulation with both anthropogenic CO2 emissions and poleward intensifying winds. The flux of anthropogenic CO2 shown in (C) is derived as the difference between the fluxes of total and natural CO2. The model simulations are described in detail in Zickfeld et al. (7).

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