云南白水台钙华记录研究：小冰期以来的高分辨率气候和环境变化

Little Ice Age (LIA) is the global cold event nearest to modern time, and the modern global warming is one of the frontier topics of earth science. Studying on the onset and ending time, detailed characteristic and the forcing factors of these climate events is important for understanding the driving mechanisms of climate changes on annual-to-decadal timescales, and for evaluating the natural and artificial factors of present global warming. As an important archive for high-resolution paleoclimate study, the fast deposited travertine can reach seasonal resolution and even higher. In this study, we propose to reconstruct geochemical records on several travertine cores drilled by Core drill produced by Pomeroy, at Baishuitai, Yunnan province. The cores will be dated by varve counting and high-presion MC-ICP-MS 230Th/U dating. Subsequently, high resolution oxygen and carbon isotopic compositions will be analyzed. Based on the study of the meteorotical records and modern travertines, we will estalish the relationships among the oxygen and carbon isotopic compositions and climatic factors as well as local environmental conditions. Then, high resolution (seasonal timescale) climate changes since the Little Ice Age will be reconstructed from the travertine at Baishuitai. Throughout this study，we attemp to confirm the onset and ending time of the little ice age and the temperature anomaly of 20th century, to detect the amplitude and frequency of secondray temperature fluctuation, and to understand the relationship between temperature and rainfall. We will compare our records with other local, regional and global records to examine the driving mechanisms of climat change on annual-to-decadal timescales, and to evaluate the natural and human factors of the climate change. The research will provide new scientific basis for forecasting the future climate change.

小冰期以来，全球气候变化既有寒冷的小冰期，又有现代的全球变暖，这些气候事件是最接近我们现代生活的气候变化，研究这个时间段的气候特征、变化规律及驱动机制，是地球科学的前沿课题之一，对评估当前全球变暖的自然和人为因素具有重要的科学意义。钙华的高沉积速率使其可以作为季节分辨率的古气候重建载体，是一个有待开发的极具优势的气候记录。本研究将利用在云南白水台钻取的多根小冰期以来沉积连续的年层状钙华岩芯，通过年纹层计数、高精度定年和高分辨率的氧碳同位素测试,在完善和深化已取得的现代钙华氧碳同位素组成与气候因子之间关系的基础上，定量重建该区小冰期以来季节性高分辨率的气候变化序列；揭示小冰期和现代暖期的发生时间、次级冷暖波动频率、幅度和速率，以及干(湿)/冷(暖)配置格局；揭示该地区百年-年际气候变化的区域响应特点并探索其驱动机制，辨识气候变化的自然和人为因素影响，为预测未来气候变化提供新的科学依据。

小冰期以来，全球气候变化既有寒冷的小冰期，又有现代的全球变暖，这些气候事件是最接近我们现代生活的气候变化，研究这个时间段的气候特征、变化规律及驱动机制，是地球科学的前沿课题之一，对评估当前全球变暖的自然和人为因素具有重要的科学意义。印度夏季风（ISM）是全球气候系统中重要的组成部分和主要的水汽来源，全新世早期高分辨率印度夏季风演化历史的重建，有利于揭示十年至百年际印度夏季风的变化特征及其驱动机制，对了解印度夏季风的运行和预测未来气候变化有着重要的意义。钙华的高沉积速率使其可以作为季节分辨率的古气候重建载体，进行古气候重建研究。为了完善和深化现代钙华氧碳同位素组成与气候因子之间的关系，并在其基础之上进行高分辨率的小冰期气候变化和全新世早期气候变化的重建研究。从2013年到2017年，采用野外采样和室内分析相结合的方法，对白水台钙华沉积点的水化学、沉积速率和钙华氧碳钙同位素进行现场监测和取样分析，并对白水台钻取的钙华岩芯进行了高精度的Th-230定年、Pb-210定年和高分辨率的氧碳同位素取样，同时也对四川黄龙张家沟钙华剖面进行了高精度的Th-230定年和高分辨率的氧碳同位素取样。结果发现：(1)沉积速率会影响钙华氧同位素组成，两者呈负相关关系；(2)水动力条件对钙华钙同位素组成有显著影响，并且钙华与沉积水体间钙同位素分馏的大小与沉积速率有关；(3)渠道系统中钙华的碳氧同位素组成不仅反映气候因子（降雨）的变化，还受系统内部物理化学过程的控制；(4)云南白水台地区小冰期的气候变化存在明显的干湿波动，并且小冰期的气候变化明显受太阳活动的控制；(5)全新世早期青藏高原东部边缘印度夏季风的变化与北大西洋气候有密切的关系，并且印度洋夏季风的变化受太阳活动的控制。