A proxy precipitation record for the Central Namib Desert using δ 13C analysis on Acacia erioloba
Date
2022
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Abstract
Namibia is one of the most arid countries in sub-Saharan Africa and aridity in the region is being exacerbated by climate change. Past climate reconstructions allow for deductions to be made regarding climate patterns and cycles; this facilitates more accurate future climate projections. There are few reliable meteorological or historical climate records for Namibia. While some long-term palaeoclimate records have been produced from proxies such as speleothems and hyrax middens, these offer relatively coarse temporal resolution. Dendroclimatological investigations can produce highresolution palaeoclimate reconstructions, with precise radiocarbon dating. Therefore, a very high level of calibration between tree rings and climatic data can be achieved. This research project uses the stable-carbon isotope approach and 14C dating on two Acacia (Vachellia) erioloba trees, (namely Husab-1 and 2) to test whether a proxy precipitation chronology for the Erongo region in central Namibia could be produced. Radiocarbon dates on the trees indicate that Husab-1 and 2 grew during the Little Ice Age (LIA) and the beginning of the modern era until the mid-20th Century CE. δ 13C analyses suggest that there was marked rainfall variability during this period, which is consistent with other palaeoenvironmental research for the Namib region, and other regions within the Summer Rainfall Zone (SRZ) of southern Africa. Although errors in the age model resulted in inaccuracies, a proxy precipitation record was produced. Comparisons between the Husab chronology and paleoenvironmental records, such as the Dante Cave speleothem records, and slack water deposits found along the Khan River, highlighted climatic variability within Namibia during the LIA. Furthermore, statistically significant relationships between Sea Surface Temperature (SST) anomalies, the Southern Annular Mode (SAM), and the proxy precipitation chronology indicate that these may have been key drivers for precipitation variability in the central Namib Desert during the past 600 years.
Description
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, University of the Witwatersrand, Johannesburg, 2022
Keywords
Proxy precipitation record, Central Namib Desert using, Climate records for Namibia