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Climate of the Past An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 03 Jun 2019

Submitted as: research article | 03 Jun 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).

Evidence of intense climate variation and reduced ENSO activity from δ18O of Tridacna 3700 years ago

Yue Hu1,2, Xiaoming Sun1,2,3,4, Hai Cheng5,6, and Hong Yan7,8,9 Yue Hu et al.
  • 1School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China
  • 2Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510275, China
  • 3School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
  • 4Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China
  • 5Institute of Global Environmental Change, Xi'an Jiaotong University, Xi’an 710054, China
  • 6Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA
  • 7State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
  • 8CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
  • 9OCCES, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China

Abstract. Tridacna is the largest marine bivalves in the tropical ocean, and its carbonate shell can shed light on high-resolution paleoclimate reconstruction. In this contribution, δ18Oshell was used to estimate the climatic variation in the Xisha Islands of the South China Sea. We first evaluate the sea surface temperature (SST) and sea surface salinity (SSS) influence on modern rehandled monthly (r-monthly) resolution Tridacna gigas δ18Oshell. The obtained results reveal that δ18Oshell seasonal variation is mainly controlled by SST and appear insensitive to local SSS change. Thus, the δ18O of Tridacna shells can be roughly used as a proxy of the local SST: a 1 ‰ δ18Oshell change is roughly equal to 4.41 °C of SST. R-monthly δ18O of a 40-year Tridacna squamosa (3673 ± 28 BP) from the North Reef of Xisha Islands was analyzed and compared with the modern specimen. The difference between the average δ18O of fossil Tridacna shell (δ18O = −1.34 ‰) and modern Tridacna specimen (δ18O = −1.15 ‰) probably implies a warm climate with roughly 0.84°C higher in 3700 years ago. The seasonal variation in 3700 years ago was slightly decreased compared with that suggested by the instrument data, and the switching between warm and cold-seasons was rapid. Higher amplitude in r-monthly and r-annual reconstructed SST anomalies implies an enhanced climate variability in this past warm period. Investigation of the El Ninõ-Southern Oscillation (ENSO) variation (based on the reconstructed SST series) indicates a reduced ENSO frequency but more extreme El Ninõ events in 3700 years ago.

Yue Hu et al.
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Yue Hu et al.
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Short summary
Tridacna, the largest marine bivalves, can shed light on high-resolution paleoclimate reconstruction in its carbonate skeleton. In this contribution, the monthly resolution of modern δ18Oshell suggest to be a proxy of SST in Xisha Islands of South China Sea. A fossil Tridacna (3673 ± 28 BP) reveals a warm, decreased seasonal variation and intense climatic variability compares with present. A reduced ENSO frequency and more extreme winter El Ninõ events occurred during that past warm period.
Tridacna, the largest marine bivalves, can shed light on high-resolution paleoclimate...