Late Pleistocene desiccation of Lake Tana, source of the Blue Nile.

塔纳湖位于埃塞俄比亚北方的高地，是世界上最大的河流之一青尼罗河的源头。令人惊讶的是，人们对这个湖的年龄和历史知之甚少：20世纪30年代的一项估计是，它是在10，000年前由熔岩坝形成的。同样，尽管尼罗河长期以来被认为是古代和现代埃及资源的关键，但对包括青尼罗河源头在内的更广泛地区的气候历史却知之甚少。我们在NERC的支持下于2003年10月和2004年9月获得的新的地球物理和岩心数据表明，该湖可能至少有40，000年的历史。我们的新数据还表明，该湖在大约16，000年前干涸，几乎可以肯定，在最后一个冰河时代的后期阶段，该湖显然是定期干涸的。这可能是因为持续了一两百年的严重干旱，而干旱是由来自北美的冰山融水淹没北大西洋时非洲季风气候的破坏造成的-海因里希事件。在这个新的PalaeoTana项目中，我们的目标是通过在塔纳湖北方盆地约10米水深、距离海岸约2公里处钻取长达100米的沉积物岩心来验证这些假设。将使用X射线荧光、X射线和彩色图像、地球物理和磁性岩心扫描技术对岩心进行高分辨率扫描，同时不损坏沉积成分。由此产生的数据集将确定过去的干化事件，将详细调查并通过与16，000年前已知干化事件的沉积物进行比较来解释。通过适当的方法，包括发光，火山灰年代学和氩-氩年代测定法对沉积物进行年代测定，将能够精确估计干旱事件的时间和持续时间。这些事件的相对时间与海洋核心的气候突变事件（特别是海因里希事件）和其他大陆记录相比，将允许对全球尺度的气候突变机制进行推断。这些数据也可以用来测试气候模型，从而帮助判断模型预测的未来气候突变的准确性。非洲这一地区过去气候和环境的长期核心记录对于了解区域环境变化（由于尼罗河对非洲东北部和地中海东部的影响）和全球气候具有重要意义。它将有助于了解海洋温度和环流的未来变化将如何影响全球气候，特别是在人口稠密的非洲和亚洲季风地区。它还将通过提供影响早期人类种群及其水、植物和狩猎资源的环境变化记录，对了解人类在非洲进化的后期阶段和向非洲以外的扩散具有重要意义。

Lake Tana, in the highlands of northern Ethiopia, is the source of the Blue Nile, one of the world's great rivers. Surprisingly, very little is known about the age and history of this lake: one estimate from the 1930's is that it was formed 10,000 years ago by a lava dam. Similarly, little is known about the climatic history of the wider region that comprises the Blue Nile headwaters, despite the fact that the Nile has long been recognized as critical to the resources of ancient and modern Egypt. New geophysical and core data, obtained by us in October 2003 and September 2004 with NERC support, show that the lake may be at least 40,000 years old. Our new data also show that the lake dried out at around 16,000 years ago, and almost certainly at apparently regular intervals during the later stages of the last Ice Age. It is possible that the lake dried because of intense droughts lasting one or two hundred years, and that the droughts were caused by disruption of Africa's monsoon climate when iceberg-laden meltwater from North America flooded the North Atlantic - the Heinrich events. In this new PalaeoTana Project, we aim to test these hypotheses by drilling a sediment core, up to 100m in length, from the northern basin of Lake Tana, in about 10m water depth, and about 2km from shore. The core will be scanned at high resolution using X-ray fluorescence, X-ray and colour imagery, geophysical and magnetic core-scanning technology, without damaging the sedimentary components. The resulting datasets will identify past desiccation events, which will be investigated in detail and interpreted by comparison to sediments of the known drying-out event at 16,000 years ago. Dating the sediments by appropriate methods including luminescence, tephrochronology, and Argon-Argon dating will allow precise estimates of the timing and duration of the drought events. The relative timing of these events in comparison with abrupt climatic events in ocean cores (especially Heinrich events), and in other continental records, will allow inferences about the global- scale mechanisms of abrupt climate change. The data can also be used to test climate models, and thus to help judge the accuracy of model-predicted abrupt climate change in the future. A long core record of past climate and environment from this part of Africa would have major significance for understanding both regional environmental change, because of the influence of the Nile on NE Africa and the eastern Mediterranean, and global climate. It will contribute to understanding how future changes in ocean temperature and circulation will affect global climate, especially in the heavily populated monsoon regions of Africa and Asia. It will also have significance for understanding the later stages of human evolution in and dispersal out of Africa, by providing a record of the environmental changes that influenced early human populations and their water, plant and hunting resources.