Change of the ENSO-related δ 18O–SST correlation from coral skeletons in northern South China Sea: A possible influence from the Kuroshio Current

Abstract

Chemical proxies are useful analogs for reconstructing physical properties of sea water, such as sea surface temperature (SST) and sea surface salinity (SSS). Time series of these inferred properties would allow for reconstructions of past El Niño–Southern Oscillation (ENSO) events, where no instrumental records exist. In this study, a monthly oxygen isotope record from a Porites coral is used to explain how past ENSO events are recorded in the coral skeletons. The sample covers a 12 year period and was collected from Nanwan Bay, Taiwan. During El Niño events the coral skeleton is shown to produce a δ 18O–SST correlation with a slope of −0.12 ± 0.04‰ °C −1. During other times, this value is significantly different, with a slope of −0.21 ± 0.04‰ °C −1. Coral that grew during El Niño summers have δ 18O values which are enriched by ∼0.2‰, relative to other times. A possible mechanism to explain this difference may be enhanced penetration of Kuroshio Current waters into the South China Sea during summer. The observed contrast in the correlation of δ 18O–SST variability in this sample supports the influence of El Niño in eastern Asia.