NOAA/WDS Paleoclimatology - Fanning Island - Coral Radiocarbon Data

Coral skeletal radiocarbon records reflect seawater d14C and are useful for reconstructing the history of water mass movement and ventilation in the tropical oceans. Here, we reconstructed the inter-annual variability in central equatorial Pacific surface water d14C from 1922-1956 using near-monthly radiocarbon measurements in a Porites sp. coral skeleton (FI5A) from the windward side of Fanning Island (3 deg 54'32""N, 159 deg 18'88""W). The most pronounced feature in this record is a large positive shift in d14C between 1947 and 1956 that coincides with the switch of the Pacific Decadal Oscillation (PDO) from a positive to a negative phase in the mid-1940s. Although the absolute d14C values from 1950 - 1955 in FI5A differ from the d14C values of another coral core collected from the opposite side of the island, both records show a large positive shift in their d14C records at that time. The relative increase in d14C of each record is consistent with the premise that a common mechanism is controlling the d14C records within each coral record. Overall, the Fanning d14C data support the notion that a significant amount of subtropical seawater is arriving at the equator but does not allow us to determine the mechanism for its transport.