Coral skeletons provide an archive of 129I concentration within tropical ocean surface waters. The total iodine concentration of Porites coral skeletons (5 ppm) is roughly 100 times higher than that of the surrounding waters (50 ppb). As a result 5 to 10 grams of coral skeleton is sufficient to prepare an iodine target (for AMS) without the use of carrier iodine. With this sample size an 8 cm cross-section drill core can easily provide sub-annual resolution for a Porites coral with typical growth rate (~ 1.5 cm/yr). To date, we have analyzed two coral records of 129I from the Solomon Islands and Easter Island that span the time range 1935-1995, encompassing the bomb-pulse period. These records are similar during the early bomb-pulse period but diverge circa 1975, suggesting that regional ocean surface currents as well as atmospheric transport are important pathways of anthropogenic iodine in the South Pacific Ocean.
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