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

Abstract

AbstractWe present seasonal ∆14C and δ18O measurements from a Galapagos coral sequence that grew during the early 20th century. Our results show that both ∆14C and δ18O values are correlated with sea surface temperature in the Niño 3.4 region and are indicators of El Niño–Southern Oscillation. There is a significant inverse correlation between ∆14C and δ18O values when ∆14C is lagged by ~2 months, indicating that sea surface temperature changes precede upwelling changes at this eastern equatorial location. We find that cold season low‐∆14C values were higher after the Pacific Decadal Oscillation (PDO) changed from a positive to a negative phase. Cold season high‐δ18O values were significantly higher after the PDO shift as well. These findings suggest that there are two sources of low‐∆14C waters that upwell at the Galapagos, Subantarctic Mode Water and shallow overturning water from the subpolar North Pacific.