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

合作研究：来自加纳博苏姆特维湖新获得的沉积物钻芯的高分辨率、低纬度古气候学

• 批准号: 0602336
• 负责人: Christopher Scholz
• 金额: $ 26.87万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0602336&HistoricalAwards=false
• 关键词: Collaborative; Research; Resolution; Low; Latitude

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.

博苏姆特维湖位于西非加纳热带森林低地的一个有一百万年历史的陨石撞击坑中。该湖在水文上是封闭的，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，并且在赤道西非拥有迄今为止最长、分辨率最高的古气候记录。知识价值：该资助研究过去~430 kyr（即回到海洋同位素阶段[MIS] 11）的年际至千年尺度的西非季风动力学。这项工作提供了深入了解热带在触发、加剧和传播气候变化以及响应全球和高纬度变化方面的作用。这项工作将产生西非气候和气溶胶在多个冰期循环中变化的第一个连续的、年代准确的陆地记录，并提供一个关键甲烷源区域的水文约束条件，并利用每年分层的沉积物来研究关于多个冰期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融事件的反应是什么？我们能否评估大冰原融化并导致间冰期条件的速度有多快？以前终止的气候逆转的性质是什么？MIS11持续了多长时间，它在热带地区是如何表现出来的，它与轨道强迫有什么关系，尤其是在最后？在温暖气候下，干旱变异性的全部范围是什么？)该项目还研究了高纬度地区的突然变化与热带地区同期事件的关系，并研究了一个假设，即~74+ kyr的博苏姆特维湖干涸事件与多巴火山喷发、北半球急剧降温和东非大湖区严重低洼同时发生，这表明了一场深刻的泛非干旱危机，这可能是造成“早期现代人类”人口瓶颈的原因，以及当时记录的非洲人外流。该研究提供了一个重要的季风气候系统在温暖和寒冷气候下快速气候变化的年-年分辨率的多代理记录。其次，本研究通过提供沿IGBP PEP-III样带的西非的新记录来解决区域模式和气候变化的阶段性问题。更广泛的影响：先前的研究表明，在社会时间尺度上，水文平衡的急剧突变可能会发生。全新世暖气候事件的成因仍然知之甚少。在许多温暖的间冰期，包括一些可能比今天更温暖的间冰期，对更长的记录的研究将进一步了解这些动力学。这项工作还将阐明关键的社会相关争议，如冰盖融化的速度有多快，以及类似全新世的MIS11间冰期是如何结束的。对美国学生和博士后的培训将是跨学科和广泛的。