NOAA/WDS Paleoclimatology - Moorea Lagoon - del18O and del13C Data

We study climate variability over interdecadal time scales from d13C and d18O records, measured in a Porites lutea coral core drilled in the Moorea lagoon. Previously, we demonstrated that the annual d18O variations reflect those in sea-surface temperature (SST), while the annual d13C variations record primarily cloud-cover changes. We apply two distinct spectral analysis methods to the d13C and d18O time series from 1853 to 1989. Our analysis of the d18O record shows a secular warming trend and a 35-year oscillation in temperatures over the last 137 years. A trend and a 34-year cycle are also found in the d13C record. The latter trend may be caused by either anthropogenic effects or a cloud-cover increase in this region of the Pacific Ocean, while the interdecadal oscillation appears to be related to changes in cloud cover, as well as in precipitation.