A Multi-Proxy Approach to Understanding Late Pleistocene Climate Change in Namibia, Botswana, and Northwestern South Africa

尽管世界各地的科学家正在开发区域古植被和古气候重建，以便更好地研究气候变化过去对这些区域的影响，但在非洲西南部进行的古环境研究相对较少。这项研究项目将是一项雄心勃勃的国际、多学科、合作的古环境研究计划的第二阶段，该计划将在包括纳米比亚、博茨瓦纳部分地区和南非在内的西南部非洲进行。在这个项目的第一阶段，研究人员取得了许多重大发现。第二阶段将继续获取南部非洲的古植被和古气候数据，这是改进目前的生物群和大气环流模型模拟所需的，以便它们能够更好地预测过去和未来的情况，包括持续全球变暖可能产生的影响。研究人员对大范围的古气候研究采用了多代理方法，以便在空间范围内评估气候的时间变化。他们将考察的地点将提供以下地区的数据：目前冬季降雨量占很大比例的地区(如纳米比亚西南部和南非西北部)，以及扎伊尔空气带来的大西洋夏季降雨量占主导地位的地区(主要是纳米比亚北部和博茨瓦纳北部)或印度洋(博茨瓦纳、南非西北部大部分地区和纳米比亚东部)。研究人员的最终目标是结合来自隆起的海洋阶地和河流沉积、泛/新月和残留的线性沙丘系统的古环境数据，以及来自泉丘、Hyrax侏儒、瀑布凝灰岩和洞穴洞穴的数据，以开发最详细和全面的非洲西南部晚更新世气候变化记录，包括全新世的高分辨率记录。他们特别感兴趣的是确定在北半球以及冰和海洋岩芯确定的重大气候事件期间非洲西南部的条件，包括最后一次冰盛期、年轻仙女木、全新世最佳时期、中世纪最佳时期和小冰期。AMS放射性碳、ICPMS U系列和光激发发光(OSL)测年将被用来为各种数据集制定年表。这个项目预计将做出一些重要的研究贡献。调查人员希望证明，在晚更新世，纳米布沙海的北部界限位于其目前的边界奎塞布河以南，如果不是干旱的话，他们会质疑沙丘的古老程度。他们将为非洲任何地方制作最详细的全新世气候变化记录，以帮助那些使用大气环流模型工作的人。它们将产生一个很长的记录(可能比现在早10万到35万年)，可以与海洋核心、冰芯和太阳变率数据进行比较，从而能够更现实地解释南部非洲过去的气候变化。研究人员不会只关注一个可能提供误导性、不完整或模棱两可的结果的数据来源，而是将古代河流、湖泊和沙丘系统过去活动增加的证据与从洞穴石笋获得的关于气候变化的更高分辨率数据结合在一起。在这些半干旱和干旱的环境中，如果没有理想的沉积物来研究花粉，他们将从古老的Hyrax侏儒那里获得花粉，从而提供至少过去5万年的古植被数据。由于该项目由来自纳米比亚、南非、西班牙和美国10个不同机构的10名科学家承担，它将促进国际合作。纳米比亚和美国学生将获得资金，以便他们能够参与研究项目，来自西班牙的一名博士后研究员也将参与其中。我们的研究结果将通过在国际期刊以及南非、纳米比亚和博茨瓦纳的期刊上发表。该奖项由美国国家科学基金会国际科学与工程办公室联合资助。

Although scientists around the world are developing regional paleovegetation and paleoclimatic reconstructions in order to better address the ways that climate change has affected those regions in the past, relatively little paleoenvironmental research has been conducted in southwestern Africa. This research project will be the second phase of an ambitious international, multidisciplinary, collaborative program of paleoenvironmental research in southwestern Africa, including Namibia and parts of Botswana and South Africa. In the first phase of this program, the investigators made a number of significant discoveries. The second phase will continue the process of acquiring the paleovegetation and paleoclimatic data for southern Africa that is needed to improve current biome and general circulation model simulations so that they can better predict past and future conditions, including the possible impacts of continued global warming. The investigators have adopted a multi-proxy approach to paleoclimate research over a broad area in order to assess temporal variations in climate in a spatial context. The sites that they will examine will provide data for areas that today receive a significant proportion of their rain in winter (such as southwestern Namibia and northwestern South Africa), as well as areas that are dominated by summer rainfall brought from the Atlantic Ocean by Zaire air (largely northern Namibia and northern Botswana) or from the Indian Ocean (Botswana, most of northwestern South Africa, and eastern Namibia). The investigators' ultimate objective is to combine paleoenvironmental data from raised marine terrace and fluvial sediments, pan/lunette and relict linear dune systems, and data from spring mounds, hyrax middens, waterfall tufas, and cave speleothems to develop the most detailed and comprehensive late Pleistocene record of climate change for southwestern Africa, including a high-resolution record for the Holocene. They are particularly interested in determining conditions in southwestern Africa during major climatic events identified in the Northern Hemisphere and in ice and marine cores, including the Last Glacial Maximum, Younger Dryas, Holocene Optimum, Medieval Optimum, and Little Ice Age. AMS radiocarbon, ICPMS U-series, and optically stimulated luminescence (OSL) dating will be used to develop chronologies for the various data sets.This project is expected to make a number of significant research contributions. The investigators expect to show that the northern limit of the Namib Sand Sea was south of its present boundary, the Kuiseb River, during the late Pleistocene questioning the antiquity of the dunes if not the aridity. They will produce the most detailed record of Holocene climate changes for anywhere in Africa to assist those working with general circulation models. They will generate a long record (possibly to between 100,000 and 350,000 years before the present) that will enable comparison with ocean core, ice core, and solar variability data, thereby allowing more realistic explanations of past climate changes in southern Africa. The investigators will not focus on just one source of data that could provide misleading, incomplete, or ambiguous results but instead will bring together evidence of past increased activity in ancient fluvial, lake, and dune systems with higher-resolution data on climate change obtained from cave stalagmites. In the absence of ideal sediments for pollen studies in these semiarid and arid environments , they will obtain pollen from dated hyrax middens, thereby providing paleovegetation data for at least the last 50,000 years. Because the project is being undertaken by ten scientists from ten different institutions in Namibia, South Africa, Spain, and the U.S., it will foster international collaboration. Namibian and American students will be provided funding so that they can participate in the research program, and one post-doctoral researcher from Spain will also be involved. The results of our research will be made available through publication in international journals, as well as in South African, Namibian, and Botswana journals. This award is jointly funded by the NSF Office of International Science and Engineering.