珊瑚记录的全新世ENSO变化及其机制研究进展

Coral records of Holocene ENSO and its revealed mechanism

厄尔尼诺-南方涛动(ElNiño-SouthernOscillation,ENSO)是地球气候系统中最强烈的年际振荡,对全球天气及气候有重要影响。全新世作为与人类关系最为密切的地质时段,重建该时段ENSO的活动历史、探索ENSO的变化规律,将有助于提高对未来ENSO预测的准确性。本文基于珊瑚这一热带海洋的高分辨率气候记录载体,首先介绍从珊瑚骨骼指标中提取ENSO信号、衡量ENSO变率的方法;再梳理珊瑚记录的ENSO变率在早、中、晚全新世的变化历史;最后总结基于珊瑚记录得出的全新世不同时间尺度的ENSO变化机制。结果显示:珊瑚记录的ENSO信号可直接从其环境代用指标的极值变化中识别;或通过谱分析、滤波等方法提取环境代用指标在时间序列中的ENSO周期,再使用阈值分析、滑动窗口等方法定量分析ENSO的频率和振幅变化。珊瑚记录显示,全新世ENSO呈波动变化的特征,总体呈现自早全新世至中全新世ENSO变率不断减弱,而晚全新世ENSO变率持续增强的趋势。基于珊瑚记录得出,岁差变化引起的地表太阳辐射分布变化是全新世百年-千年尺度ENSO变化的主要因子,而气候系统内部驱动可能是全新世年际-年代际尺度ENSO波动的主要原因。与全新世一万多年的时间跨度相比,珊瑚记录的时间窗口累计仅数百年,远未达到揭示EN-SO活动规律和变化机制的程度,因此未来需要进一步延长珊瑚记录的时间序列长度、扩大珊瑚记录的空间区域来源,以揭示ENSO变化的规律和机制。

The El Niño-Southern Oscillation(ENSO)is the strongest interannual oscillation in the Earth's climate system,which has a significant impact on global weather and climate.The Holocene is the geological time most closely related to humans,and reconstructing the activity history of ENSO and exploring the change pattern of ENSO in this period will help to improve the accuracy of future ENSO prediction.In this regard,based on coral,a high-resolution climate record carrier of tropical oceans,we firstly introduce the method of extracting ENSO sig-nal from coral skeleton index and measuring ENSO variability;then compares the history of ENSO variability in early,middle and late Holocene;and finally summarizes the mechanism of ENSO variability in different time scales in Holocene based on coral record.The results show that the ENSO signals in the coral records can be dir-ectly identified from the extreme changes of their environmental proxies;or the ENSO cycles of the environment-al proxies on the time series can be extracted by spectral analysis and filtering,and then the frequency and amp-litude changes of ENSO can be quantitatively analyzed by using threshold analysis and sliding window methods.The coral records show that the Holocene ENSO is characterized by fluctuating changes,with a general trend of decreasing ENSO variability from the early to middle Holocene and increasing ENSO variability in the late Holo-cene.Based on the coral record,it is concluded that the change in surface solar radiation distribution due to the age difference is the main factor of the century-millennium scale ENSO variation in the Holocene,while the in-ternal drive of the climate system may be the main reason for the interannual-interdecadal scale ENSO fluctuation in the Holocene.However,compared with the long time span of the Holocene,the accumulated time window of the coral record is only a few hundred years,which is far from revealing the patterns and mechanisms of ENSO activity.Therefore,it is necessary to further extend the time series and increase the spatial area of the coral record in the future to reveal the patterns and mechanisms of ENSO variability.