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

季风影响着地球的大片地区，每年影响着数亿人的生计。本博士论文研究项目的目的是精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、海洋条件、冰量、海因里希事件、邦德周期）。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，洞穴石笋提供了精确确定年代的新信息。该项目的主要目标是：(1)为美国东南部建立第一个高分辨率、连续、准确的全新世气候变化记录；(2)制作并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方的两个洞穴和美国阿拉巴马州的一个洞穴中的石笋来实现这一目标。通过观察石笋生长轴上的发光、颜色、O和C稳定同位素的变化，以及碳酸盐岩石学，他将获得气候和季风变化的详细记录。该学生希望比较亚洲季风在冰期和间冰期之间的变化，并详细记录中国南部和美国东南部的全新世气候变化，以显示全新世早期劳伦泰德冰原的持续存在如何影响源自墨西哥湾的季风活动。这项研究的一个独特之处在于，它将使用电钻机从大型石笋中获取垂直岩心，而这些岩心以前是无法进行科学研究的。这种方法最大限度地减少了对石笋的破坏，但也允许人们接触到石笋的长期环境变化记录。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。所获得的知识将有利于社会的长期规划。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，而不会将石笋从洞穴中取出并破坏洞穴环境。这样做的长期好处是为后代保存洞穴环境。

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.