Collaborative Research: High-Resolution, Low-Latitude Paleoclimatology from Newly Acquired Sediment Drill Cores from Lake Bosumtwi, Ghana"

博苏姆特维湖位于西非加纳热带森林低地的一个有百万年历史的陨石撞击坑中。该湖在水文上是封闭的，已知对降水/蒸发平衡和西非季风的强度非常敏感。博苏姆特维湖包含了热带地区为数不多的、长期的年度层状沉积物记录之一，并且拥有迄今为止赤道西非地区最长、分辨率最高的古气候记录。学术价值：该基金研究了过去~430 kyr（即，海洋同位素阶段（Marine Isotopic Stage，MIS 11）这项工作使人们深入了解热带地区在引发、加剧和传播气候变化以及应对全球和高纬度变化方面的作用。这项工作将产生西非气候气溶胶变化在多个冰川循环中的第一个连续的日期明确的陆地记录，并提供对关键甲烷源区的水文限制，并使用年度分层沉积物来研究有关多个冰川终止的确切时间和变化模式的全球重要问题（例如，低纬度地区对冰川消退事件的反应是什么？我们能否评估大冰盖融化的速度并导致间冰期的条件？以前终止的气候逆转的性质是什么？MIS 11有多长时间，它在热带地区是如何表现的，它与轨道强迫有什么关系，特别是在最后？在温暖的气候条件下，干旱的全部变化范围是什么？）该项目还研究了高纬度地区的突然变化如何与热带地区的同时代事件相关，并研究了以下假设：约74+ kyr的Bosumtwi湖干涸事件与多巴火山爆发、北方半球急剧降温和东非五大湖严重的低水位是同时代的，这表明泛非洲存在严重的干旱危机，这可能是造成“早期现代人类”人口瓶颈的原因，当时记录了非洲人的外流。这项研究提供了一个重要的季风气候系统在温暖和寒冷的气候期间的快速气候变化的多代理记录。第二，这项研究涉及区域模式和分阶段的气候变化提供新的记录，从西非，这是沿着IGBP PEP-III的样带。更广泛的影响：以前的研究表明，戏剧性的突变水文平衡可能会发生在一个频谱的社会时间尺度。暖气候全新世事件的原因仍然知之甚少。这项对更长记录的研究，钻过许多温暖的间冰期，包括一些可能比今天更温暖的间冰期，将进一步了解这些动态。这项工作还将阐明有关冰盖融化速度的关键社会相关争议，以及类全新世MIS 11间冰期如何结束。美国学生和博士后的培训将是跨学科和广泛的。

Lake Bosumtwi lies in a million-year-old meteorite impact crater located in the tropical forest lowlands of Ghana, in West Africa. The lake is hydrologically closed and known to be very sensitive to the precipitation/evaporation balance and the strength of the West African Monsoon. Lake Bosumtwi contains one of a very few, long annually laminated sediment records in the tropics, and has by far the longest, highest-resolution paleoclimate record in equatorial West Africa.Intellectual Merit: This grant studies interannual to millennial-scale West African monsoon dynamics over the last ~430 kyr (i.e., back through Marine Isotopic Stage [MIS] 11). This work provides insight into the role of the tropics in triggering, intensifying and propagating climate changes, as well as in responding to global and highlatitude changes. This work will produce the first continuous well-dated terrestrial record of West African climate & aerosol variability over multiple glacial cycles, and provide hydrologic constraints on a key methane source region, and use the annually-laminated sediments to examine globally significant questions regarding the exact timing and patterns of change over multiple glacial terminations (e.g., What is the low-latitude response to deglaciation events, and can we assess how fast large ice sheets melt and lead to interglacial conditions? What is the nature of climatic reversals on previous terminations? How long was MIS11, how was it manifested in the tropics, and how does it really relate to orbital forcing, particularly at the end? What is the full range of drought variability during warm climates?)The project also examines how the abrupt changes of the high-latitudes are related to coeval events in the tropics, and examines the hypothesis that a Lake Bosumtwi dessication event at ~74+ kyr is coeval with the Toba eruption, dramatic Northern Hemisphere cooling, and severe lowstands in the East African Great lakes, indicating a profound pan-African aridity crisis, that is perhaps responsible for the "early modern human" population bottleneck, and African exodus documented for that time. The study provides multiproxy records of rapid climate change at annual-decadal resolution of an important monsoonal climate system during both warm and cold climates. Second, this study addresses regional patterns and phasing of climate change by providing new records from West Africa, which is along the IGBP PEP-III transect.Broader Impacts:Previous studies indicate that dramatic abrupt shifts in hydrologic balance can occur on a spectrum of societal time scales. The cause(s) of the warm-climate Holocene events remain poorly understood. This study of the longer record, drilled through many warm interglacials, including some perhaps warmer than today, will further understanding of these dynamics. This work will also illuminate key societally-relevant controversies regarding how fast ice sheets can melt, and how the Holocene-like MIS11 interglacial ended. Training of US students and a post-doc will be interdisciplinary and extensive.