4个代表站点的珊瑚δ^(18)O数据对热带印度洋气候变率的反演能力分析

Reconstruction of climate variability of the tropical Indian Ocean based on coral δ^(18)O data from four representative sites

珊瑚中的δ^(18)O含量可以高精度地记录热带海洋中的气候变率及气候变化信息,从而弥补器测观测时间长度有限的缺陷,为反演过去长期的气候状况提供了可能。热带印度洋的气候模态通过海气相互作用影响周边区域甚至全球的气候,具有重要的研究意义。本文对比分析了1880—1999年间热带印度洋4个站点(肯尼亚、坦桑尼亚、塞舌尔、明打威)的珊瑚δ^(18)O数据,研究了其对热带印度洋气候的反演情况。结果显示,珊瑚δ^(18)O对海表温度(sea surface temperature,SST)的长期变化趋势反演良好,珊瑚δ^(18)O与局地SST在季节循环中保持一致,且在低温季节对SST的变化更为敏感。此外,4个站点的珊瑚δ^(18)O对印度洋海盆模态(Indian Ocean Basin Mode,IOBM)和印度洋偶极子模态(Indian Ocean Dipple Mode,IODM)有一定的表征能力,并且δ^(18)O记录的热带印度洋年际变率受年代际变率调制。本文的研究结果表明,珊瑚δ^(18)O数据对于了解古气候时期热带印度洋气候变率具有重要的指示意义,但同时也需要综合考虑不同站点的信息来完整地反映印度洋在历史时期的气候变化情况。

The coralδ^(18)O data can precisely record climate variation and change of the tropical ocean,making up the shortage of deficient instrumental observations and providing us with the possibility of retrieving long-term paleoclimate conditions.The climate modes of the tropical Indian Ocean influence the climate of the surrounding region and even the globe through ocean-atmosphere interaction;so they are of great significance in climate study.In the present study,coralδ^(18)O data from 1880 to 1999 at four sites located in the tropical Indian Ocean(Kenya,Seychelles,Tanzania,Mentawai)are used to study their ability to reproduce past climate in the tropical Indian Ocean.First,coralδ^(18)O and SST changes are consistent on the long-term trend.Second,coralδ^(18)O coincides nicely with local SST in terms of seasonal cycle,and is more sensitive to SST variation in cold seasons.What is more,coralδ^(18)O at the four sites can describe changes of IOBM(Indian Ocean Basin Mode)and IODM(Indian Ocean Dipole Mode),but the interannual variability of the tropical Indian Ocean recorded by coralδ^(18)O is modulated by interdecadal variation.This study suggests that theδ^(18)O data from coral is an essential indicator of paleoclimate in the tropical Indian Ocean.Different sites'information should be taken into account to reflect past climate change in the Indian Ocean.