Collaborative Research: The Lake Malawi Drilling Project - A long, high-resolution record of abrupt climate change in the southern tropics of East Africa

合作研究：马拉维湖钻探项目——东非南部热带气候突变的长期高分辨率记录

• 批准号: 0602454
• 负责人: Tom Johnson
• 金额: $ 34.99万
• 依托单位: University of Minnesota Duluth
• 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 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0602454&HistoricalAwards=false
• 关键词: Collaborative; Research; Lake; Malawi; Drilling

Drilling the large rift lakes of the East African Rift Valley has been a high priority goal since the 1980s. In 2005 the Lake Malawi Scientific Drilling Project acquired more than 623 m of core at two sites (92% recovery), in seven holes, including one hole in 600 meters of water that reached a subbottom depth of 380 m. The project triple-cored a high-resolution site in the north basin, which extends back 80kyr, double cored the deep site in the central basin covering the past 200 kyr, and single-cored the deep site to 380 m, dated at 1.5 million years at the base. These drill-cores represent the longest, continuous record of high-resolution climate change available in the continental tropics, and they offer the potential to secure high-fidelity signals of East African effective moisture and temperature at a scale of decades/centuries over the length of the core. Located at the southern end of the East African Rift Valley (9S-14S), Lake Malawi's great depth (max. of 700 m), extent (more than 580 km long), and prolonged stratification with anoxic bottom waters assure well preserved, at times laminated, sediments recording regionally-significant southern hemisphere climate signals. This grant 1) addresses specific paleoclimate questions posed below, and 2) completes the initial core descriptions over the full duration of the cored interval. The research will address these paleoclimate questions: What was the direction, magnitude and timing of effective moisture, wind, and temperature change of this southern tropical setting, on a millennial scale, during the past two glacialinterglacial cycles? Do the observed shifts coincide in a consistent manner with SST variability in the tropical oceans, or with the North Atlantic thermohaline circulation? What is the lake level history of Malawi, and how does it compare with the methane record of the polar ice cores, which is interpreted to be a globally averaged measure of tropical moisture on the continents? Does the observed evidence for abrupt climate change in the Lake Malawi and other parts of East Africa coincide with known events from other regions on Earth, e.g., Heinrich or Dansgaard/Oeschger events? What are the direction, duration and magnitude of these changes? What was the tropical climate behavior during earlier periods of global warmth (e.g. Marine Isotope Stage 5e, or alternatively MIS 11), and how abruptly did these periods begin and end?The secondary objective is to complete the initial core descriptions, including reconnaissance sampling and analysis at low resolution over the past 1.5 million years. Did the climate of this site in the southern tropics respond only to changes in low-latitude precessional insolation (23-19 kyr) or also to high-latitude ice volume (100 kyr and 41 kyr) forcing, in the last part of the Pleistocene? Completing the reconnaissance, lowresolution analyses of this unique set of samples serves the greater scientific community, positioning it to undertake more elaborate studies on these cores in the future. Sampling and analyses are limited to key proxies, focused on quantifying past effective moisture, dust and temperature. Proxy analyses are carried out on a decade-century scale in the time intervals of selected events, and on a millennial scale over the broader intervals.The broader impact of this research addresses the role of climate on human evolution, assists in interpreting the tectonic history of the East African Rift, and leads to a better understanding of the controls of climate on species evolution in lakes. For instance, new Malawi records as well as those from other African sites indicate a period of pronounced aridity prior to ~75 kyr. Was this aridity crisis responsible for the early human population bottleneck in evidence for that period? This collaborative project engages scholars in-training at the postdoctoral, graduate, and undergraduate levels, as well as African colleagues, and involves outreach components both in Africa and the U.S.

自1980年代以来，钻探东非裂谷的大湖区一直是优先目标。 2005年，马拉维湖科学钻井项目在两个地点（恢复92％）的核心收购了超过623 m的核心，其中包括600米水中的一个孔，达到了380 m的子底部深度。该项目在北盆地的三重高分辨率遗址延伸了80kyr，将中央盆地的深部占地覆盖了过去的200 kyr，并将深层地点单置至380 m，其日期为150万年。这些钻核代表了大陆热带地区可用的高分辨率气候变化的最长，连续的记录，它们提供了在核心长度上以数十年/百年的规模确保东非有效水分和温度的高保真信号的潜力。位于马拉维湖的大深度（最多700 m），范围（长580公里），长时间分层，有时保存着良好的水域，有时有时会录制了区域性明显的南半球，位于东非裂谷的南端（9s-14s），范围（长达580公里），长度（长580公里），长度（长580公里），长时间分层。这项赠款1）解决下面提出的特定古气候问题，以及2）在整个芯间间隔内完成了初始核心描述。这项研究将解决这些古气候问题：在过去的两个冰川互联循环中，这种南部热带环境的有效水分，风和温度变化的方向，大小和时机是什么？观察到的移位是否与热带海洋中的SST变异性或北大西洋热盐循环以一致的方式重合？马拉维的湖泊历史是什么，它与极地冰芯的甲烷记录相比，这被解释为在大陆上的全球平均热带水分量度？观察到的马拉维湖气候变化和东非其他地区突然变化的证据是否与地球其他地区（例如Heinrich或Dansgaard/Oeschger事件）的已知事件相吻合？这些变化的方向，持续时间和幅度是什么？在全球温暖的早期（例如海洋同位素阶段5E或MIS 11）中，热带气候行为是什么，这些时期的开始和结束是如何突然开始的？次要目标是完成初始核心描述，包括在过去1500万年中以低分辨率进行侦察采样和分析。南部热带地区该地点的气候是否仅对低纬度预抗沉积物（23-19 KYR）或高纬度冰的体积（100 kyr和41 kyr）强迫的变化作出反应？完成侦察的低分辨率分析，对这组独特的样本为更大的科学界提供了服务，将其定位为对这些核心进行更详细的研究。采样和分析仅限于关键代理，重点是量化过去有效的水分，灰尘和温度。 Proxy analyses are carried out on a decade-century scale in the time intervals of selected events, and on a millennial scale over the broader intervals.The broader impact of this research addresses the role of climate on human evolution, assists in interpreting the tectonic history of the East African Rift, and leads to a better understanding of the controls of climate on species evolution in lakes.例如，新的马拉维记录以及其他非洲遗址的记录表明，在〜75 Kyr之前，有一个明显的干旱时期。这一时期的证据中，这种干旱危机是否造成了早期人口瓶颈？这个合作项目与学者在博士后，研究生和本科级别以及非洲同事中进行培训，并涉及非洲和美国的外展成分