A 350,000 - Year History of Rainfall and Temperature in Tropical East Africa

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该奖项支持对2005年从非洲马拉维湖底部回收的两个岩心进行分析。这些核心包含大约350，000年的温度和降雨代理从马拉维湖中央盆地。马拉维湖钻探项目的初步结果迄今提供了：（1）对过去15万年来东非干旱的复发和强度的惊人新见解，（2）对过去湖泊生态系统动态的初步估计，（3）令人信服的证据表明非洲热带这一地区的气候与两极跷跷板之间存在联系，以及（4）该地区的热历史可以追溯到75，000年前。本项目解决了以下问题：1.温度和降雨量在多大程度上跟随两半球的日照强迫？2.马拉维盆地的温度和湿度变化与大气CO2和CH 4浓度之间有什么关系？3.在过去的50万年里，马拉维盆地的温度和降雨量的千年尺度变化的性质是什么？4.马拉维盆地的温度和降雨量在多大程度上对热带太平洋和印度洋的海面温度状况作出反应？该项目通过分析来自长链脂肪酸的del-D记录和保存在马拉维湖沉积物中的陆地植被长链正构烷烃中的del-13 C记录，获得过去降雨量的估计值。对过去温度的估计是基于海洋环境的古温度代用指标TEX 86。这一方法从东非马拉维湖和坦噶尼喀湖的先前工作中取得了可喜的成果。该小组继续改进马拉维长岩芯的年龄模型，重点是在岩芯中几个富碳酸盐层段发现的碳酸盐结核的U/Th测年。这些日期补充了碳酸盐丰度记录的岁差调整，热带非洲的气候历史预示着未来将再次发生严重和持久的干旱，这将对该区域的人类福祉产生巨大影响。这项研究将提供的数据将是非常宝贵的，可以与过去几十万年来热带地区的海洋沉积物和洞穴记录进行比较，并测试气候模型的准确性，这些模型是改善非洲大陆人口稠密地区长期天气预报所必需的。该项目涉及研究生和本科生在实验室分析，并在解释和传播结果的各个方面，通过研究生论文研究和本科生的研究机会。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This award supports analyses of two cores recovered in 2005 from the floor of Lake Malawi, in Africa. These cores contain approximately 350,000 years of temperature and rainfall proxies from the central basin of Lake Malawi. Initial results from the Lake Malawi Drilling Project have thus far provided: (1) surprising new insights into the recurrence and intensity of drought in East Africa for the past 150,000 years, (2) a preliminary estimate of past lake ecosystem dynamics, (3) compelling evidence for a tie between the climate in this part of the African tropics with the bipolar see-saw, and (4) a thermal history of the region that extends back 75,000 years. This project addresses the following questions: 1. To what extent do temperature and rainfall follow insolation forcing of either hemisphere? 2. What is the relationship between temperature and humidity shifts in the Malawi basin and concentrations of atmospheric CO2 and CH4? 3. What is the nature of millennial-scale variation in temperature and rainfall in the Malawi basin over the past ~500,000 years? 4. To what extent do temperature and rainfall in the Malawi basin respond to the sea-surface temperature regime of the tropical Pacific and Indian Oceans? The project obtains estimates of past rainfall from analyses of the del-D record derived from long-chain fatty acids and of the del-13C record preserved in the long-chain n-alkanes of terrestrial vegetation preserved in Lake Malawi sediment. Estimates of past temperature are based on a paleotemperature proxy for the marine environment called TEX86. This approach has provided promising results from previous work on both Lake Malawi and Lake Tanganyika in East Africa. The group continues to improve on the age model of the long Malawi drill core, focusing on U/Th dating of carbonate nodules that are found at a few, carbonate-rich intervals in the core. These dates are supplemented with precessional tuning of the carbonate abundance record.The climate history of tropical Africa portends a future of recurring severe and long-lasting drought that will have enormous impact on human welfare in the region. The data that will be provided from this research will be invaluable for comparison to marine sediment and speleothem records from the tropics that span the past few hundred thousand years, and for testing the accuracy of climate models that are necessary to improve long-term weather forecasts for this heavily populated portion of the African continent. The project involves graduate and undergraduate students in laboratory analyses and in all aspects of interpretation and dissemination of results, through graduate thesis research and undergraduate research opportunities.