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.
