黄土高原末次冰期以来气候变化模式及突变事件的高分辨率石笋记录研究

黄土-古土壤序列较好地揭示了第四纪以来轨道尺度亚洲季风变迁模式及其响应机制，但其年龄的不确定性在一定程度上限制了人们对短尺度东亚季风行为特征的认识。本项目基于黄土高原东缘若干洞穴石笋为研究对象, 通过高密度、高精度230Th定年，重建全新世与末次冰期MIS3阶段中早期年际-数十年际分辨率的东亚季风演化序列，诊断突发事件在季风边缘区的表现形式和准确年代，细化DO12、DO14事件的内部结构特征包括转型方式和持续时间，探讨亚千年尺度东亚季风与高纬气候的联系；获得研究区全新世季风演化的精细过程，剖析早、中、晚全新世季风变化的阶段性特征，明确研究区确实存在9.2-8ka 弱季风时段、8.2ka、4.2ka等气候突变事件，合理评估全新世季风演化的时空变化规律及其驱动机制。与葫芦洞等记录不同，北方洞穴记录的气候突变事件振荡幅度更大，这种差异有可能在东亚夏季风动力学机制认识上取得新突破。

Previous studies on loess have made significant advances in understanding long-term evolution of the Asian Monsoon and its forcing mechanism, little is yet know short-term climate oscillations during the last glacial period and Holocene due to its inadequate age control. Here, we will firstly reconstruct high-resolution stalagmite δ18O records in Chinese Loess Plateau, based on larger numbers of 230Th ages from different Caves, registering a detailed history of the East Asian Summer Monsoon (EASM) from 80ka to the present. These new data allows us to investigate the timing, duration, amplitude and structure of both Dansgaard-Oeschger (D-O) and Heinrich (H) events occurred in the northwestern monsoonal marginal zone, where may be more sensitive to high-low latitude climate changes. We will assess the detailed pattern of EASM variability during DO8, DO12, DO14 and YD events and constrain the regional correlation between various climates in different time windows. Also, we will present so far the best detailed Holocene EASM history for the Loess Plateau in north China, which allow us to define the timing of abrupt climate events occurred in north China, such as the 8.2ka BP, 4.2ka BP events and divide three distinct phases for the evolution of the EASM. In addition, we find a relative weakened monsoon interval between 9.2 and 8.0ka BP., which is not reported in previous published papers. Likewise, we will compare our record with the other independent-dated cave records to evaluate the spatial and temporal pattern of Holocene climate changes over a larger portion of China and test different mechanisms proposed by people. New data show that the amplitude of both the D-O events and the 8.2ka BP event is larger than that of the Hulu and Dongge, which is possible to give us an insight into the mechanisms controlling the EASM changes during the last glacial period.