The influence of air and sea exchange on the carbon isotope distribution in the sea

We explore here the influence of the temperature dependence of isotope fractionation between atmospheric CO 2 and ocean ΣCO 2 on the distribution of carbon isotopes in the ocean. This is accomplished by an analysis of departures from the expected Redfield tie between PO 4 and δ 13 C. We find that for the surface ocean, the temperature influence largely compensates for the biologic influence. In the deep ocean, the temperature influence imprinted at the sites of deepwater formation reduces somewhat the biologically induced difference between the carbon isotope ratios for deep waters produced in the northern Atlantic and in the Antarctic. These same features are reproduced in the Hamburg ocean model. In order to assess the impact of changes in the ratio of ocean mixing rate to wind speed, we have made a model run in which CO 2 exchange rates between air and sea were everywhere doubled. As expected, the influence of the thermodynamic effect on the oceanic carbon isotope distribution is magnified.