Influence of Orbital Forcing on ENSO variability - new insights from an annually laminated speleothem

Future climate change scenarios suggest the African continent will become increasingly susceptible to extreme changes in rainfall (droughts and flooding). Attempts to predict rainfall variability in Africa have been limited by our poor understanding of what controls past variability; for example characterising the influence of El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on African hydrology. The warmer conditions of the early Pleistocene when the Walker Circulation and ENSO become established offer an analogue to future African climate variability. We propose to investigate these issues by utilising a unique annually laminated half a million year long speleothem deposit from South Africa - the Buffalo Cave flowstone. Building on our previous millennial scale record of African rainfall, we now propose to expand proxy resolution to annual for band thickness and decadal for stable isotopes. The program of annual band thickness counting and stable isotope measurement will generate a rainfall record of unprecedented length and temporal resolution, enabling us to investigate the controls on African rainfall variability at a range of timescales from inter-annual to orbital. The Buffalo Cave flowstone record covers the time period ca. 2.0-1.5 Ma, based on preliminary dating evidence, and crosses one of the most important climate transitions in the Tropics, the intensification of the Walker circulation between 1.8 and 1.7 Ma. We will thus be able to characterise changes in South African rainfall before, during and after the establishment of this fundamental feature of the modern climate system. It will allow us to understand the evolution of the ENSO system and the long term influence of the IOD. This research will provide new insights into rainfall variability in the past, and will aid our predictions of future rainfall in Africa.

- We will host a workshop on ENSO modelling and palaeodata intercomparison at Birkbeck/UCL in December 2013 with Joy Singarayer (Project Partner). Our work will test a number of hypotheses about the functioning of the tropical climate system, the results of which will need to be disseminated to the wider climate modeling community. This will be a an ideal forum for the dissemination of our results and an opportunity to foster future collaboration with the UK palaeoclimate modelling community.

- We will host a workshop on African Palaeoclimate and human evolution at Birkbeck/UCL in April 2014. This workshop will bring together palaeoclimatologists, palaeoanthropologists and evolutionary modellers to discuss our findings on the causes and consequences of African climate change. Our work will offer new paradigms for the understanding of hominid ecology across a range of timescales from an individual life-span to the origin and extinction of species.

- Research collaboration between the palaeoclimatic and and palaeoanthropological communities in the UK is currently limited. There is an increasing number of young academics working within this field, but there is no infrastructure to support their research. We will address this problem by setting up an interest group to focus on this topic. Researchers at key UK institutions (including Cambridge, Liverpool John Moores, Liverpool University, Oxford, Sheffield, UCL, York and others) will be invited to partake in our networking activities. This will help to increase the profile of UK research within this academic discipline and ensure that it continues to thrive in the future.

- We will set up a web-page for the general public to explain current thinking on the climatic context of human evolution. We will brief the media on the key findings of our research. The Principal Investigator will attend the NERC training course on communicating science to the public.

- This work will be incorporated into poster displays at the local heritage center, giving visitors a feel for the scope of climate change research in the Makapansgat Valley. We will brief local tourist guides on the key findings of our work. Dr Hopley will develop contacts with key South African stakeholders (SAHRA, University of Witwatersrand) and attend the annual University of Sheffield expedition to Makapansgat.