三峡库区高分辨率石笋记录的末次间冰期以来季风气候转型与突变事件研究

The oxygen isotope records of stalagmites from Yangkou Cave of Nanchuan and Xueyu cave of Fengdu dated with 230Th dating methods provides variations of the Asian monsoon with a high resolution of 1~30 years since 130ka BP in Yangtze Gorges Reservoir, which fills the blank of stalagmite records of this time in the upper and middle reaches of the Yangtze River region during that period. In this study, we will anatomize the internal details of the structure and he oscillation mode of a typical monsoon abrupt events, and explore Millennium-century-scale oscillation laws and driving mechanism of monsoon climate since. Meanwhile, we will discuss also variation characteristics of the glacial-interglacial transitions period in the Asian monsoon region and accurately measure the duration of transition of periods glacial-interglacial. A key issue is whether Cave stalagmite δ18O values can be interpreted by the δ18O in meteoric precipitation and cave temperature during calcite precipitation. Thus, based on the research of modern carbonate-water oxygen isotope system and the instrumental observation data, this study probes into the stalagmite oxygen isotopic composition and its implications and discusses the relationship between monsoon precipitation, Historical documents and meteorological data, which would help us improve understanding the variations of the Asian monsoon and the future climate. By the comparing simultaneous high resolution time series which were published worldwide and systematic analyzing the global and regional climate signals contained in the series, we will construct the monsoon climate's variation in eastern China since 130ka BP. This would help us improve understanding the monsoon variations and spatial characters of monsoon in the eastern China, which prevents and mitigates of climate disasters and provides scientific data and basis for decision making in the Three Gorges reservoir area.

根据长江三峡库区雪玉洞和羊口洞石笋230Th定年和δ18O数据，建立库区130ka BP以来精确定年、高分辨率、连续的石笋记录，分辨率达到1-30年，填补长江上游地区该时段石笋记录研究空白；深入分析典型季风突变事件内部细节结构、振荡模式，探讨季风气候千年-百年尺度振荡规律和驱动机制；剖析末次间冰期-末次冰期季风气候转型时期细节变化特征，精确测算转型时段持续时间；对洞穴现代碳酸盐-洞穴滴水氧同位素体系进行监测分析，进一步明确季风区石笋δ18O值记录气候信息机理；通过与全球已发表相同时段、高精度古气候序列对比，系统分析序列中所含全球性和区域性的气候信号，探讨和建立中国东部地区末次间冰期以来季风气候变化模式，为理解该时段中国季风环流演化和空间分布特征以及建立中国石笋记录解析的末次间冰期以来千年尺度气候事件全球对比基准积累基础数据，也为三峡库区气候灾害防治和减灾提供科学数据和决策依据。

近年来随着极端气候事件、各种地质灾害频繁发生，对未来气候变化的预测显得越来越重要。想要准确的预测未来气候，我们就必须对过去气候变化有深刻地了解和研究，特别是与我们所处的全新世最接近的末次间冰期气候。因此，本项选取亚洲季风区的重庆周边的洞穴作为研究区域，利用石笋的氧碳同位素、微量元素和U/Th年龄数据，重建了三峡库区建立了130ka BP 以来精确定年、高分辨率、连续的石笋碳氧同位素和微量元素时间序列，探讨了末次间冰期以来的季风气候变化突变事件和气候驱动因素： . 研究结果表明Y-02δ18O记录的下千年至百年尺度气候波动事件与格陵兰冰芯记录紧密相连。Y-02记录显示：D/O18事件大概开始于64.6ka B.P.，结束于63.6ka，持续时间近1.0ka；石笋δ18O值在短短300a多时间由-7.63‰偏负到-8.98‰，偏负了1.35‰，随后逐渐偏正。H6事件开始的时间在60.9±0.5ka B.P.，H6事件在持续约1100年后，在约59.8±0.6ka B.P.，H6事件结束。石笋灰度研究显示石笋δ18O记录偏重时，石笋灰度值增加；反之，灰度序列表现出“峰”构造。进一步分析发现，羊口洞石笋灰度序列与树轮Δ14C数据、太阳黑子数据呈显著正相关，说明太阳活动是驱动石笋灰度序列变化的一个重要因素。Y02石笋的功率谱分析结果表明百年尺度的太阳辐射是60~90 ka BP时段气候的主要驱动机制，并且小波分析显示出60~90 ka BP时段气候变化还具有5ka左右的周期。本项研究为深入理解该时段中国大陆季风环流演化和空间分布特征积累了实践经验和基础数据，为三峡库区气候灾害的防治和减灾提供科学数据和决策依据。