Pleistocene Indian Monsoon Rainfall in the Core Convective Region, Bay of Bengal

在印度-亚洲季风区，人们依靠季风降雨来获得水和农业，在许多地区，地下水的采取量已经超过了补给率。对季节性降雨的依赖只会随着时间的推移而增加。树木年轮记录表明，过去1000年的干旱状况超出了历史上已知的量级。该项目旨在了解控制这些极端干旱时期的过程。降水和干旱的长期变化间接记录在近海海底缓慢积累的沉积物的化学、物理和生物组成中。通过分析在孟加拉湾获得的岩心沉积物，可以重建过去50万年的海面温度和季风降雨的变化。在这个项目中，记录将用于两个目的。首先，他们将确定季风降雨对大气中二氧化碳含量、全球冰量和太阳辐射强迫变化的敏感性，所有这些在这段时间间隔内都是众所周知的。其次，这些记录将有助于检查全球季风区模式的准确性。该项目的结果将有助于了解与其他地区极端干旱有关的过程。该项目为研究生和本科生提供培训。在阿拉伯海、南海和中国东部长江流域进行了更新世夏季风重建。这些区域在近代被起源于南亚热带印度洋的大尺度大气流动态地联系在一起，这些大尺度大气流横跨阿拉伯海、印度、孟加拉湾、印度支那、南中国海和中国东部。在轨道时间尺度上，来自这些地区的结果是不同的，要么指向风和季风水汽输送的脱钩，要么指向对代用季节性的误解。目前的这种状态导致了对季风敏感性的基本驱动机制的强烈分歧解释，包括日照、海洋/大气能量交换、冰量和温室气体，所有这些因素都影响了我们对突变和千年尺度变化的理解。季风降雨将在孟加拉湾北部和印度重建，这是地球上对流最活跃的地区。将对印度东北部边缘U1446（2015年1月钻探）过去50万年的样本进行分析。将产生多个独立的记录，每个记录跨越过去500 ka，采样间隔为1至2 ka，清楚地解决了轨道尺度的变化。多代理数据集将区分为解释不同轨道尺度解释而提出的假设。

In the Indo-Asian monsoon region the population depends on monsoonal rains for water and agriculture, and in many regions groundwater withdrawal already exceeds recharge rates. The dependence on seasonal rainfall will only increase over time. Tree-ring records indicate drought conditions over the past 1000 years that are beyond magnitudes known historically. This project seeks to understand the processes controlling these periods of extreme drought. Long-term changes in precipitation and drought are indirectly recorded in the chemical, physical, and biological composition of sediments that slowly accumulate offshore on the sea floor. By analyzing sediments from drill cores obtained in the Bay of Bengal, changes in sea surface temperature and monsoonal rainfall over the past 500,000 years can be reconstructed. During this project the records will serve two purposes. First, they will establish the sensitivity of monsoonal rains to changes in the carbon dioxide content of the atmosphere, global ice volume, and solar radiation forcing, all of which are very well known over this time interval. Second, the records will help to check the accuracy of global models of monsoonal regions. The results of the project will aid in understanding the processes associated with extreme drought in other regions. The project provides training for a graduate student as well as undergraduate students.Pleistocene summer monsoon reconstructions have been produced from the Arabian Sea, the South China Sea, and the Yangtze River basin of eastern China. These regions are dynamically linked in the modern by large-scale atmospheric flow originating in the southern subtropical Indian Ocean, spanning the Arabian Sea, India, the Bay of Bengal, Indochina, the South China Sea and eastern China. At orbital time scales, results from these regions are divergent, pointing either to a decoupling of winds and monsoonal moisture transport, or to a misinterpretation of proxy seasonality. This current state has resulted in strongly divergent interpretations of monsoon sensitivity to fundamental driving mechanisms including insolation, ocean/atmosphere energy exchange, ice volume, and greenhouse gasses, all of which factor into our understanding of abrupt and millennial-scale variability as well. Monsoon rainfall will be reconstructed over the northern Bay of Bengal and India, among the most convectively active regions on Earth. Samples spanning the past 500,000 years from the northeast Indian Margin Site U1446 (drilled January, 2015) will be analyzed. Multiple independent records will be generated, each spanning the past 500 ka at sample intervals of 1 to 2 ka, clearly resolving orbital-scale variance. Multi-proxy data sets will differentiate between hypotheses put forward to explain the divergent orbital scale interpretations.