Western Pacific coral δ18O records of anomalous Holocene variability in the El Niño-Southern Oscillation

Helen V. McGregor*, Michael K. Gagan

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    139 Citations (Scopus)

    Abstract

    Skeletal oxygen isotope ratios in Holocene Porites corals from northern Papua New Guinea record decreases in sea surface temperature (SST) and rainfall during El Niño events. Threshold analysis of seven fossil coral δ18O records spanning the period 7.6-5.4 ka (thousand years ago) shows 8-12 El Niño events/century, significantly less than the 23 events/century recorded by the NINO3.4 Index. The coral reconstructions also show a 15% reduction in El Niño event amplitude for 7.6-5.4 ka, compared to today, which is greater than the suppression given by model studies. In contrast, large and protracted El Niño events are identified for 2.5-1.7 ka. Taken together, the results indicate a nonlinear atmospheric response to Holocene changes in El Niño SST anomalies. We propose that small changes in tropical SST gradients, the positioning of the Intertropical Convergence Zone, and the Pacific tradewind climatology modify the impact of El Niño events on western Pacific rainfall.

    Original languageEnglish
    Pages (from-to)L11204 1-4
    JournalGeophysical Research Letters
    Volume31
    Issue number11
    DOIs
    Publication statusPublished - 16 Jun 2004

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