Seasonal radiocarbon and oxygen isotopes in a Galapagos coral: Calibration with climate indices

We present seasonal Delta C-14 and delta O-18 measurements from a Galapagos coral sequence that grew during the early 20th century. Our results show that both Delta C-14 and delta O-18 values are correlated with sea surface temperature in the Nino 3.4 region and are indicators of El Nino-Southern Oscillation. There is a significant inverse correlation between Delta C-14 and delta O-18 values when Delta C-14 is lagged by similar to 2 months, indicating that sea surface temperature changes precede upwelling changes at this eastern equatorial location. We find that cold season low- Delta C-14 values were higher after the Pacific Decadal Oscillation (PDO) changed from a positive to a negative phase. Cold season high- delta O-18 values were significantly higher after the PDO shift as well. These findings suggest that there are two sources of low- Delta C-14 waters that upwell at the Galapagos, Subantarctic Mode Water and shallow overturning water from the subpolar North Pacific.