Evidence from giant-clam δ18O of intense El Ninõ-Southern Oscillation-related variability but reduced frequency 3700 years ago

Yue Hu, Xiaoming Sun, Hai Cheng, Hong Yan

Research output: Contribution to journalArticlepeer-review

Abstract

Giant clams (Tridacna) are the largest marine bivalves, and their carbonate shells can be used for highresolution paleoclimate reconstructions. In this contribution, δ18Oshell was used to estimate climatic variation in the Xisha Islands of the South China Sea. We first evaluate sea surface temperature (SST) and sea surface salinity (SSS) influence on the modern resampled monthly (r-monthly) resolution of Tridacna gigas δ18Oshell. The results obtained reveal that δ18Oshell seasonal variation is mainly controlled by SST and appears to be insensitive to local SSS change. Thus, the δ18O of Tridacna shells can be roughly used as a proxy of local SST: a 1% δ18Oshell change is roughly equal to 4.41 °C of SST. The r-monthly δ18O of a 40-year-old Tridacna squamosa (3673±28 BP) from the North Reef of the Xisha Islands was analyzed and compared with the modern specimen. The difference between the average δ18O of the fossil Tridacna shell (δ18O D -1:34 %) and the modern Tridacna specimen (δ18O D -1:15 %) probably implies a warm climate, roughly 0.84 °C, 3700 years ago. The seasonal variation 3700 years ago was slightly lower than that suggested by modern instrumental data, and the transition between warm and cold seasons was rapid. Higher amplitudes of reconstructed r-monthly and r-annual SST anomalies imply an enhanced climate variability during this warm period. Investigation of the El Ninõ-Southern Oscillation (ENSO) variation (based on the reconstructed SST series) indicates reduced ENSO frequency but increased ENSO-related variability and extreme El Ninõ winter events 3700 years ago.

Original languageEnglish (US)
Article number2020
Pages (from-to)597-610
Number of pages14
JournalClimate of the Past
Volume16
Issue number2
DOIs
StatePublished - Apr 1 2020

Bibliographical note

Funding Information:
Financial support. This research has been supported by the National Key R&D Program of China (2018YFA0702605), the National 13th Five Year Plan project (DY135-R2-1-01, DY135-C1-1-06), National Nature Science Foundation of China (41876038, 41877399, 91128101, 41888101), State Key Laboratory for Mineral Deposits Research in Nanjing University (no. 20-15-07), Chinese Academy of Sciences (QYZDB-SSW-DQC001), and the Qingdao National Laboratory for Marine Science and Technology of China (QNLM2016ORP0202).

Funding Information:
This research has been supported by the National Key RandD Program of China (2018YFA0702605), the National 13th Five Year Plan project (DY135-R2-1-01, DY135-C1- 1-06), National Nature Science Foundation of China (41876038, 41877399, 91128101, 41888101), State Key Laboratory for Mineral Deposits Research in Nanjing University (no. 20-15-07), Chinese Academy of Sciences (QYZDB-SSW-DQC001), and the Qingdao National Laboratory for Marine Science and Technology of China (QNLM2016ORP0202)

Publisher Copyright:
© Author(s) 2020.

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