The dominant processes controlling the magnitude and spatial distribution of the preindustrial air-sea flux of CO are atmosphere-ocean heat exchange and the biological pump, coupled with the direct influence of ocean circulation resulting from the slow time-scale of air-sea CO gas exchange equilibration. The influence of the biological pump is greatest in surface outcrops of deep water, where the excess deep ocean carbon resulting from net remineralization can escape to the atmosphere. In a steady state other regions compensate for this loss by taking up CO to give a global net air-sea CO flux of zero. The predominant outcrop region is the Southern Ocean, where the loss to the atmosphere of biological pump CO is large enough to cancel the gain of CO due to cooling. The influence of the biological pump on uptake of anthropogenic CO is small: a model including biology takes up 4.9% less than a model without it. Our model does not predict the large southward interhemispheric transport of CO that has been suggested by atmospheric carbon transport constraints.
|Number of pages||19|
|Journal||Global Biogeochemical Cycles|
|Publication status||Published - 1 Jun 1999|