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Carbon isotope constraints on vertical mixing and air-sea CO 2 exchange

2003; American Geophysical Union; Volume: 30; Issue: 24 Linguagem: Inglês

10.1029/2003gl018049

1944-8007

Stewart Fallon, T. P. Guilderson, K. Caldeira,

Isotope Analysis in Ecology

We have developed a ∼45 year carbon isotope record (δ 13 C, Δ 14 C) from the coralline sponge Acanthochaetetes wellsi from Vanuatu in an effort to examine air‐sea CO 2 exchange using both the δ 13 C Suess effect and the bomb‐ 14 C transient. From 1953 to 1999 δ 13 C decreased by 0.9‰. Pre‐bomb Δ 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 CO 2 exchange rate produces the overall observed shape of the pre‐post bomb Δ 14 C record and the general large scale features of the δ 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.