Climatic trends and interdecadal variability from south‐central Pacific coral records

We study climate variability over interdecadal time scales from δ 13 C and δ 18 O records, measured in a Porites lutea coral core drilled in the Moorea lagoon. Previously, we demonstrated that the annual δ 18 O variations reflect those in sea-surface temperature (SST), while the annual δ 13 C variations record primarily cloud-cover changes. We apply two distinct spectral analysis methods to the δ 13 C and δ 18 O time series from 1853 to 1989. Our analysis of the δ 18 O 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 δ 13 C 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.

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