Carbon isotope constraints on vertical mixing and air-sea CO2 exchange -: art. no. 2289

We have developed a similar to45 year carbon isotope record (delta(13)C, Delta(14)C) from the coralline sponge Acanthochaetetes wellsi from Vanuatu in an effort to examine air-sea CO2 exchange using both the delta(13)C Suess effect and the bomb-C-14 transient. From 1953 to 1999 delta(13)C decreased by 0.9%. Pre-bomb Delta(14)C is -59%, consistent with coral based estimates from the same region and the post-bomb maximum (+121%) is achieved in 1973. A 1-D box-diffusion model was employed to quantify vertical diffusivity and air-sea exchange rates. The model suggests that a low vertical diffusion rate (0.1 cm(2) s(-1)) coupled with a moderate CO2 exchange rate produces the overall observed shape of the pre-post bomb Delta(14)C record and the general large scale features of the delta(13)C time series. These parameters are on the low end of values used in ocean-carbon GCMs but are consistent with microscale tracer experiments.