How important are Southern Hemisphere wind changes for low glacial carbon dioxide? A model study

The response of atmospheric CO2 to modifications in the strength and position of Southern Hemisphere westerlies is examined with the Bern3D ocean model. The model responds more sensitively to changes in the wind amplitude than to variations in latitudinal position. Depending on the model setup, a 50% reduction in wind strength leads to a CO2 drawdown of 3–34 ppm, while a 50% increase results in a rise of 10–24 ppm. A poleward shift of 5° lowers CO2 by 2–16 ppm whereas an equatorward shift of 5° induces a CO2 increase of 2–14 ppm. Physical and biological mechanisms equally contribute to the modeled changes in atmospheric CO2. Our results are in conflict with the hypothesis that Southern Hemisphere wind changes are responsible for the low atmospheric CO2 concentrations during glacial periods.