基于石笋记录的小冰期与“8.2 ka BP”事件的对比研究

全新世气候突变事件是全球变化研究的热点，但对其行为特征与动力学机制的认识仍存在不足。本文选取贵州董哥洞2支高分辨率、高精度定年的石笋（DX1和DA）δ18O记录，分析小冰期和“8.2 ka BP”事件期间亚洲夏季风强度变化的结构特征与其驱动机制。通过两个突变事件的精细对比，发现两者在持续时间、振荡幅度和转型特征等方面均有很好的相似性，尤其是均显示出“两谷一峰”的结构性特征。北高纬地区淡水注入导致大西洋经向翻转流（AMOC）的减弱可能是触发“8.2 ka BP”事件的重要驱动力，这暗示具有相似结构特征的小冰期弱季风事件可能也响应于AMOC机制。将小冰期时期石笋δ18O记录与指示AMOC变化的北大西洋放射性碳数据进行对比，发现两者具有相似的变化过程，这表明在早晚全新世不同气候背景条件下，AMOC仍能够通过影响南北半球温度梯度的变化而影响低纬热带辐合带位置的移动，进而调控千-百年尺度低纬季风区水文循环的时空变化。 

A comparative study on the little ice age and the“8.2 ka BP”event based on two stalagmite records from the Dongge cave,Southwest China

Abrupt climate change in the Holocene has attracted much attention for its behavior and mechanism, and becomes a research focus in study of the global change. Here we provide two high-precision 230Th dated high-resolution speleothem δ18O records from the Dongge Cave, southwestern China to explore the structural features and dynamic mechanism of the little ice age （LIA） and the“8.2ka BP”event in Asian summer monsoon changes. Comparing two events in speleothem records in detail suggests that the two events are similar in duration, oscillation amplitude with a typical “valley-peak-valley” structure. Freshwater discharge and its resulting in weakening of the Atlantic meridional overturning circulation （AMOC） may be the primary driving force for the“8.2ka BP”event. It implies that the weak monsoon events with similar structural features is also response to the AMOC mechanism.Furthermore, our δ18O record during the LIA is broadly similar to the local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology from the north Icelandic shelf. This consistence suggests that AMOC plays a primary role in driving low-latitude hydrological circulation via shifts in the mean position of the intertropical convergence zone.