SEASONAL RADIOCARBON VARIATION OF SURFACE SEAWATER RECORDED IN A CORAL FROM KIKAI ISLAND, SUBTROPICAL NORTHWESTERN PACIFIC
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AbstractABSTRACT. A coral radiocarbon (∆14C) investigation with a high time-resolution is crucial for reconstructing secular and seasonal ∆14C changes in the surface seawater which potentially reflect ocean circulations and dynamic ocean-atmosphere interactions. The ∆14C values of a modern coral (Porites sp.) from Kikai Island, southern Japan, in the subtropical northwest-ern Pacific, were determined for the period of 1991−1998 at a monthly resolution. A coral ∆14C time series for the 8 yr indi-cated seasonal cycles superimposed on a secular decreasing trend of 3.8 ‰ per yr. The seasonal amplitude of the coral ∆14C was about 18 ‰ on the average, and the minimum ∆14C was observed in late spring and summer. The ∆14C changes were tentatively explained by horizontal oceanic advections around Kikai Island or over the wide range of the equatorial and sub-equatorial Pacific.