Eastern Lesotho represents a unique alpine environment, situated in the temperate latitudes but at an altitude of >2800 m.asl. The rugged terrain results in considerable orographic rainfall annually, brought in both from the warm Indian Ocean to the east during summer convective storms, and the colder Atlantic Ocean to the south carried by the westerlies in winter. Palaeoenvironmental reconstructions for southern Africa provide evidence for a northward displacement in the latitudinal extent of the westerlies during the Last Glacial Maximum, resulting in a significantly larger proportion of winter precipitation in the eastern Lesotho highlands, and arguably the potential for the formation of niche glaciers.
The principal aim of this PhD is to better constrain the temporal shifts in seasonality of the dominant precipitation in eastern Lesotho throughout the Holocene period. This will mainly be explored through the analysis of oxygen isotope signals in diatom silica, extracted from several wetlands in the region.
Key objectives will be to:
1) Determine the accuracy with which the oxygen isotope signal from contemporary diatoms in wetlands reflect the precipitation seasonality for the region
2) Use the oxygen isotope signatures from diatoms through peat core profiles to reconstruct Holocene changes in precipitation seasonality in Eastern Lesotho
3) Compare the results of this to the alternate seasonality proxies published for the region to assess their efficacy in capturing seasonality shifts
Policy Impact of Research:
The outcomes of this research will be of interest to climatologists concerned with atmospheric circulation changes in southern Africa over time, and how abrupt events are integrated into the global system.
Research Relating to this Project:
Fitchett, J.M., Grab, S.W., Bamford, M.K., Mackay, A.W. (2016) A multi-disciplinary review of late Quaternary palaeoclimates and environments for Lesotho. South African Journal of Science 112, 24-32
Mackay, A. W., Swann, G. E. A., Brewer, T. S., Leng, M. J., Morley, D. W., Piotrowska, N., Rioual, P., & White, D. (2011). A reassessment of late glacial – Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach. Journal of Quaternary Science 26, 627-634.
Fitchett, J.M., Grab, S.W., Bamford, M.K., Mackay, A.W. (2017) Late Quaternary research in Southern Africa: progress, challenges and future trajectories. Transactions of the Royal Society of South Africa 72, 280-293.