Doctoral Dissertation Research: Monsoonal Climate of China and the Southeastern U.S.A. During the Late Pleistocene and Holocene

季风影响地球大片地区，每年影响数亿人的生计。这项博士论文研究项目的目的是准确记录季风活动随时间的变化，并了解导致这些变化的因素(太阳辐射、海洋状况、冰量、海因里希事件、邦德循环)。目前关于过去季风活动的大部分知识来自海洋和冰芯、湖泊沉积物和黄土-古土壤序列。然而，近年来，洞穴石笋提供了准确的年代和新的信息。该项目的主要目标是(1)为美国东南部开发第一个高分辨率、连续和准确测年的全新世气候变化记录；(2)制作和比较中国西南部和美国东南部晚更新世和全新世的气候记录；(3)研究影响季风活动的外部因素。这位博士生将通过研究中国南部的两个洞穴和美国阿拉巴马州的一个洞穴的石笋来完成这项工作。通过观察石笋生长轴线上发光、颜色、O和C稳定同位素以及碳酸盐岩相的变化，将获得气候和季风变化的详细记录。这名学生希望比较亚洲季风在冰期和间冰期之间的变化，并对中国南部和美国东南部的全新世气候变化进行详细记录，以显示劳伦蒂德冰盖持续到全新世早期是如何影响起源于墨西哥湾的季风活动的。这项研究的一个独特方面将是使用电动钻机从以前科学研究无法获得的大型石笋中获得垂直岩心。这种方法将对石笋的损害降至最低，但允许访问其长期的环境变化记录。通过了解过去季风变化的方式和原因，研究人员可能能够更好地预测未来的变化。所获得的知识将有助于社会的长期规划。该项目是与中国教师和学生的合作研究，因此将促进国际合作。此外，如果新的钻探计划成功，它将为科学家提供一种研究石笋的方法，而不会将它们从洞穴中移除并破坏洞穴环境。这样做的一个长期好处是为子孙后代保护洞穴环境。

Monsoons impact large areas of the Earth, and affect the livelihoods of hundreds of millions of people each year. The objective of this doctoral dissertation research project is to precisely document changes in monsoon activity over time and to understand the factors (solar radiation, ocean conditions, ice volume, Heinrich events, Bond cycles) that have caused these changes. Much of the present knowledge about past monsoon activity has come from ocean and ice cores, lake sediments, and loess-paleosol sequences. However, in recent years, cave stalagmites have provided precisely dated, new information. The project's principal aims are (1) to develop the first high-resolution, continuous, and accurately dated Holocene record of climate change for the Southeastern U.S.A., (2) to produce and compare late Pleistocene and Holocene records of climate in Southwestern China and the Southeastern U.S.A., and (3) to examine the external factors that have influenced monsoon activity. The doctoral student will do this by studying stalagmites from two caves in Southern China and one in Alabama, U.S.A. Detailed records of climate and monsoon variability will be obtained by looking at variations in luminescence, color, O and C stable isotopes, and carbonate petrography along the growth axes of stalagmites. The student hopes to compare Asian monsoon variability between glacial and interglacial intervals and to produce detailed records of Holocene climate change in Southern China and the Southeastern U.S.A. that will show how the persistence of the Laurentide Ice Sheet into the early Holocene affected monsoon activity originating in the Gulf of Mexico. A unique aspect of the research will be the use of an electrical drilling rig to obtain vertical cores from large stalagmites that previously were not accessible to scientific research. This approach minimizes damage to the stalagmite but allows access to its long record of environmental change. By understanding how and why monsoons have changed in the past, researchers may be able to better predict future changes. The knowledge gained will benefit societal long-term planning. This project is a collaborative study with Chinese faculty and students and thus will foster international collegiality. In addition, if the new drilling program is successful, it will provide scientists with a way to study stalagmites without removing them from caves and damaging the cave environment. A long-term benefit of this will be the preservation of cave environments for later generations.