UC Irvine

We present seasonal Δ14C and δ18O measurements from a Galapagos coral sequence that grew during the early 20th century. Our results show that both Δ14C 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 Δ14C and δ18O values when Δ14C 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- Δ14C 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-Δ14C waters that upwell at the Galapagos, Subantarctic Mode Water and shallow overturning water from the subpolar North Pacific. © 2014. American Geophysical Union. All Rights Reserved.