%0 Journal Article %T Evidence from giant-clam ¦Ä¹⁸O of intense El Nin£¿¨CSouthern Oscillation-related variability but reduced frequency 3700 years ago %A Cheng %A Hai %A Hu %A Yue %A Sun %A Xiaoming %A Yan %A Hong %J - %D 2020 %R https://doi.org/10.5194/cp-16-597-2020 %X

Abstract. Giant clams (Tridacna) are the largest marine bivalves, and their carbonate shells can be used for high-resolution paleoclimate reconstructions. In this contribution, ¦Ä¹⁸O_shell 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 ¦Ä¹⁸O_shell. The results obtained reveal that ¦Ä¹⁸O_shell seasonal variation is mainly controlled by SST and appears to be insensitive to local SSS change. Thus, the ¦Ä¹⁸O of Tridacna shells can be roughly used as a proxy of local SST: a 1 ¡ë ¦Ä¹⁸O_shell change is roughly equal to 4.41 ^¡ãC of SST. The r-monthly ¦Ä¹⁸O of a 40-year-old Tridacna squamosa (3673¡À28 BP) from the North Reef of the Xisha Islands was analyzed and compared with the modern specimen. The difference between the average ¦Ä¹⁸O of the fossil Tridacna shell (¦Ä¹⁸O $= - 1.34$ ¡ë) and the modern Tridacna specimen (¦Ä¹⁸O