NOAA/WDS Paleoclimatology - Northern South China Sea Porites Coral d13C Data during the mid-Holocene

Coral skeleton d13C is a routinely measured indicator in modern insolation change research, but the knowledge of environmental and climatic signals recorded in its seasonality during geological time is sparse. In this study, we present eight Porites coral d13C records from the mid-late Holocene to the present from the northern South China Sea (NSCS). Compared with the main control factors for modern d13C changes, coral d13C seasonality in the NSCS since the mid-Holocene shows a long-term decreasing trend, which is consistent with the change trend as orbital-induced (precession) insolation seasonal amplitude. By excluding other influencing factors, we speculate that the stronger coral d13C seasonality (18.8%) over the mid-Holocene than modern period is attributable to the metabolic effect, which predicts the stronger coral d13C seasonality under stronger insolation seasonality. Our study has implications for coral d13C seasonality as a potential indicator to record past insolation information under different climatic backgrounds.

珊瑚骨骼δ¹³C（d13C）是现代太阳辐射（insolation）变化研究中的常规测定指标，但目前针对地质历史时期中其季节性变化所记录的环境与气候信号的相关认知仍较为匮乏。本研究报道了来自南海北部（NSCS）的8份全新世（Holocene）中晚期至现代的滨珊瑚（Porites）骨骼δ¹³C记录。相较于现代δ¹³C变化的主要控制因子，南海北部自全新世中期以来的珊瑚骨骼δ¹³C季节性变化呈现长期下降趋势，该趋势与轨道驱动（orbital-induced）的岁差（precession）引发的太阳辐射季节性振幅变化趋势一致。在排除其他影响因素后，我们推测全新世中期珊瑚骨骼δ¹³C季节性变化幅度（18.8%）高于现代的现象可归因于代谢效应——该效应预示，太阳辐射季节性越强，珊瑚骨骼δ¹³C季节性变化幅度便越高。本研究表明，珊瑚骨骼δ¹³C季节性变化可作为潜在指标，用于重建不同气候背景下的古太阳辐射信息。