Project highlights

  • Utilisation of a novel palaeoenvironmental archive for dryland regions – the communal latrines of the rock hyrax
  • Application of analytical and numerical methods to provide new insights into drivers of climatic variability across centennial to multi-millennial timescales.
  • Fieldwork in southern Africa supported by an established international research team focused on African palaeoclimates

Overview

Southern Africa lies within a critical transitional zone of the global oceanic and atmospheric circulatory systems. Its response to future global climatic change and to palaeoclimatic changes (e.g. over Pleistocene glacial-interglacial cycles) has therefore attracted international scientific interest. The region is however challenging to work in, largely because its semi-arid climate does not favour the preservation of palaeoenvironmental and palaeological archives. In recent years a novel approach to address this using the stratified communal latrines of the Rock Hyrax (Chase et al., 2012; Figure 1) – as led by the supervisory team – has resulted in the creation of remarkable high-resolution records of long-term climate change. Highlights include the recent publication of a composite 50,000 year record for the whole Namib Desert (Chase et al., 2019a).

As more hyrax midden records have been developed, one of the most striking and challenging findings is the apparent spatial variability in Pleistocene-Holocene climatic trends, particularly along the southern and western margins of South Africa, close to the boundaries of the summer (tropical) /winter (temperate) rainfall zones (Figure 1; Chase and Quick, 2017; Chase et al., 2019b). This led us to hypothesise that spatial patterns in climate, particularly at millennial scales, were/are driven by complex interactions between the tropical and temperate components of the regional circulation. Understanding how these patterns manifest in space and time will provide both key insights into the functioning of the regional climate system, and a greater understanding of likely regional manifestations of hydrological change under future warming scenarios.

The aim of this PhD therefore is to interrogate this spatial-temporal patterning further, in terms of: 1) enhancing the spatial resolution/sampling density of our archives to validate and refine knowledge of (palaeo)hydroclimatic gradients; 2) utilising additional proxies (leaf wax dD) to unpick the causes of arid/humid trends (e.g. water sources); 3) synthesising these new site/proxies with a suite of formal time-series analyses; and 4) considering these records in terms of mechanistic synoptic scale climatic systems (see Chase et al., 2017). From this, the PhD aims to provide detailed new insights into long-term interactions of Southern Hemisphere tropical-temperate climatic systems.

Host

University of Leicester

Theme

  • Climate and Environmental Sustainability
  • Organisms and Ecosystems

Supervisors

Project investigator

  • Andrew Carr, University of Leicester

 

Co-investigators

  • Brian Chase, CNRS, France
  • Lynne Quick, Nelson Mandela Metropolitan University, South Africa
  • Arnoud Boom, University of Leicester

How to apply

Methodology

To address these questions, this project will develop several new hyrax midden records, sampling new sites recently identified and applying a multi-isotope analysis approach. The project therefore contains both field (South Africa) and laboratory stages. Analyses will be carried out in the University of Leicester Stable Isotope laboratory and will include stable nitrogen and carbon isotope analyses (insights into aridity and vegetation response, respectively), in conjunction with compound-specific analysis of leaf wax n-alkanes to obtain deuterium isotope records. The latter is a key step that will link these archives to palaeo-rainfall amounts and/or rainfall water sources, potentially allowing us to untangle the synoptic drivers of this apparent spatial-temporal climatic variation. To this end, new data will be integrated with our existing published and unpublished records, also requiring the student to develop and/or apply numerical methods for spatial-temporal analyses of the climatic trends, utilising for example, various time-series analysis methods (e.g. wavelet analysis).

Training and skills

You will attain a high level of competence in cutting-edge analytical techniques, including isotope ratio mass spectrometry, lipid injection gas chromatography mass spectrometry (GC/MS) analysis and compound-specific stable isotope analysis of plant biomarkers. You will be trained in mass spectrometry and mass spectra interpretation. To complete the palaeoclimatic reconstructions you will work with multi-proxy data sets and create high-resolution age-depth models using radiocarbon methods and (e.g.) Bayesian modelling approaches. You will also be trained in the synthesis of palaeoclimatic data and particularly, methods of time series analysis of climate data.

 

Partners and collaboration

You will join the HYRAX project team, who have been working on these methods for ~15 years. Carr and Boom have strong track records in southern African palaeoecology and the development of stable isotope/geochemical proxies. Carr has 19 years’ experience researching African palaeoclimate. Boom directs the University of Leicester isotope facility. You will be co-supervised by Dr Brian Chase at (CNRS, Montpellier), the leading expert on hyrax middens and African palaeoclimate. Additional supervision will be provided by one of South Africa’s leading palaeoecologists Dr Lynne Quick (Nelson Mandela Metropolitan University, South Africa).

Further details

Contact Andy Carr asc18@le.ac.uk

https://le.ac.uk/study/research-degrees/funded-opportunities/centa-phd-studentships

Possible timeline

Year 1

Field sampling of newly located midden sites, and field surveys for new midden sites. Initial training in sample preparation and analysis for Elemental Analysis and bulk d15N and d13C analysis via isotope ratio mass spectrometry. Initial training in solvent extraction methods for leaf waxes, GC/MS, mass spectrometry and GC-IRMS.

Year 2

Second field sampling season for new midden sites located during year 1, presentation of first records from year 1 field sampling, initial analyses of new and existing spatial-temporal records, with training in age model construction and time series analysis;

Year 3

Development of first synthesis of winter rainfall and year-round rainfall palaeohydrological records, synthesis of late Pleistocene palaeohydrology across regional rainfall zones. Publication of data and presentation at international conferences is anticipated from year 2 onwards.

Further reading

Carr, A.S., Chase, B.M., Boom, A., Medina-Sanchez, J. (2016). Stable isotope analysis of rock hyrax faecal pellets, hyraceum and associated vegetation in southern Africa: implications for dietary ecology and palaeoenvironmental reconstructions. Journal of Arid Environments 134, pp. 33-48.

Chase, B.M., Scott, L., Meadows, M.E., Gil-Romera, G., Boom, A., Carr, A.S., Reimer, P.J., Truc, L., Valsecchi, v., Quick L.J. (2012). Rock hyrax middens: a palaeoenvironmental archive for southern African drylands. Quaternary Science Reviews 56, pp. 1-19.

Chase, B.M., Chevalier, M., Boom, A., Carr A.S. (2017) The dynamic relationship between temperate and tropical circulation systems across South Africa since the Last Glacial Maximum. Quaternary Science Reviews 174, pp. 54-62.

Chase B., Quick, L.J. (2017) Agulhas forcing of Holocene climate change in South Africa’s southern Cape. Quaternary Research. 90, pp. 303-309.

Chase, B.M., Niedermeyer, E.M., Boom, A., Carr, A.S., Chevalier, M., He, F., Meadows, M.E., Ogle, N., Reimer, P.J. (2019) Orbital controls on Namib Desert hydroclimate over the past 50,000 years. (2019a) Geology, 47(9) pp. 867-871

Chase, B.M., Boom, A., Carr, A.S., Chevalier, M., Quick, L.J., Verboom, G.A., Reimer, P.J. (2019b) Extreme hydroclimatic response gradients within the western Cape Floristic Region of South Africa since the Last Glacial Maximum. Quaternary Science Reviews 219 pp. 297-307.

Herrmann, N., Boom, A., Carr, A.S., Chase, B.M., West, A.G., Zabel, M., Schefuß, E. (2017) Hydrogen isotopic fractionation of leaf wax n-alkanes in soils from southern African ecosystems. Organic Geochemistry 109, pp. 1-13

COVID-19

While some fieldwork is planned for this project, should travel be prevented, large quantities of sample materials are already in the Universities at Leicester and Montpellier and could be used to generate primary data without field campaigns (sub-samples posted to Leicester for analysis). There are large numbers of unanalysed samples in Montpellier which could be analysed in the lab at the University of Leicester in the event of covid restrictions that still permit research labs to remain open. Depending on the abilities and interest of the appointed student, the focus of the project could also be shifted towards a greater component focused on (re)-analysis of existing datasets using novel time series methods, which could be conducted off campus with secondary data.