Abrupt Climate Change During Marine Isotope Stage 3 in Southern Tropical Africa: Multiproxy Reconstructions from Lake Tanganyika

海洋同位素第三阶段(MIS3)是在距今约30,000年到60,000年前的一段时间，其特点是在北半球的许多地点记录到了大规模的、突然的千年尺度的变暖。南极洲和南中纬度地区的记录表明，当北半球变暖时，南半球变冷，这是海洋和大气中“两极拉锯”的一部分。然而，几乎没有来自南部热带或热带非洲的记录来测试这种模式的空间范围，尽管热带在同步、传播和触发千年尺度的气候变化方面具有潜在的重要性。这笔赠款将利用坦噶尼喀湖的沉积物岩心调查热带非洲南部MIS3千年尺度的变异性。该项目将应用敏感的新指标，包括脂肪酸的del-D、TEX86古温度计、del-15N、del-13C和%生物硅，以加速器质谱仪碳14测年为基础，在年代学框架内重建湖泊的有效降水、温度和古湖泊变化。这项工作将对热带南部千年尺度的可变性、触发和传播气候突变的机制、热带非洲“冰川干旱”的演变以及坦噶尼克湖上升流和生产力的控制提供重要的洞察。智力优势：了解千年尺度气候变化的空间模式将产生对理解其潜在物理和机制至关重要的信息，并将为测试气候模型模拟气候突然变化的能力提供基本数据。在气候突变期间，南半球热带对半球间的热量和水分传输至关重要，但南热带，特别是热带非洲，在MIS3记录网络中的代表性很差。广泛的影响：这项研究将提供一个气候变化的新记录，该地区容易发生干旱，人口稠密，其气候历史鲜为人知。这项研究将促进研究古气候的多学科方法，并将产生一篇研究生论文和对本科生进行跨学科实验室技术培训。坦噶尼喀湖是非洲最重要的湖泊之一，在裂谷盆地地质学、湖泊特有作用、湖泊学和古气候学研究中发挥着重要作用。这项工作将提供对湖泊湖沼学和生产力的长期控制的洞察，并将使用创新的新工具来调查沉积记录。

Marine Isotope Stage 3 (MIS3), a period from ~30,000 to 60,000 years before present, is characterized by large, abrupt millennial-scale warmings recorded at numerous sites in the northern hemisphere. Records from Antarctica and the southern mid-latitudes suggest that the southern hemisphere cools when the North warms as part of a 'bipolar seesaw' in the oceans and atmosphere. However, there are virtually no records from the southern tropics or from tropical Africa to test the spatial extent of this pattern, despite the potential importance of the tropics in synchronizing, propagating, and triggering millennial-scale climate change. This grant will investigate MIS3 millennial-scale variability in southern tropical Africa using sediment cores from Lake Tanganyika. The project will apply sensitive new proxies including the del-D of fatty acids, the TEX86 paleothermometer, del-15N, del-13C, and % biogenic silica to reconstruct effective precipitation, temperature, and paleolimnologic variability in the lake within an chronologic framework based on accelerator mass spectrometry carbon-14 dating. This work will provide important insight into millennial-scale variability in the southern tropics, the mechanisms triggering and propagating abrupt climate changes, the evolution of "glacial aridity" in tropical Africa, and the controls on upwelling and productivity in Lake Tanganyika.Intellectual Merits: Understanding the spatial patterns of millennial-scale climate changes will yield information critical to understanding their underlying physics and mechanisms, and will provide fundamental data to test the ability of climate models to simulate abrupt climate change. The southern hemispheric tropics are crucial to interhemispheric heat and moisture transfer during abrupt climate changes, yet the southern tropics, and in particular tropical Africa, are poorly represented in the network of MIS3 records.Broader Impacts: This research will provide a new record of climate variability from a drought-prone, densely inhabited region whose climate history is poorly known. This study will promote multidisciplinary approaches to investigating paleoclimate, and will result in one graduate student dissertation and the training of undergraduate students in cross-disciplinary laboratory techniques. Lake Tanganyika is one of the most important lakes in Africa for studies of rift basin geology, lacustrine endemism, limnology, and paleoclimatology. This work will provide insight into the long-term controls on the lake's limnology and productivity, and will use innovative new tools to investigate the sedimentary record.