Understanding climate change in the tropical Pacific and specifically the region of convective rainfall known as the South Pacific Convergence Zone (SPCZ), is vital for the millions of people who live in island archipelagos (Brown et al., 2020; Sear et al., 2020). Unfortunately, climate models perform poorly in this region and measured rainfall data are limited. This constrains our understanding of the response of Pacific climate to a range of drivers that operate over different time scales from event (tropical cyclones), inter-annual (ENSO) to centennial (LIA). Our understanding of the mechanisms by which the tropical Pacific climate changes are improving, but there is a widely recognised need for new palaeoclimate proxy records from the tropical Pacific region (Brown et al., 2020; Sear et al., 2020) to better inform climate models and to test hypotheses based on observational data. This project has the potential to provide important high-resolution data (potentially sub-annual) and new biomarker records from sites in the Cook islands and French Polynesia, with which to facilitate a step-change in our understanding and to test hypotheses about external drivers of tropical Pacific climate (e.g. IPO, Atlantic multi-decadal variability, Southern Annular mode).
This project will analyse novel laminated lake sediment records (>7000 years) and swamp records from the Southern Cook Islands and French Polynesia. Initial analysis suggest that the Cook Island core contains seasonal laminations, meaning the record is unprecedented for this region and that it has the potential to reconstruct a sub-annual hydroclimate record for the majority of the Holocene, enabling testing of hypotheses concerning behaviour of the SPCZ in response to ENSO and IPO forcing, but also longer-term drivers resulting from changes in ocean circulations and sea surface temperatures. The successful candidate will use a range of techniques including Scanning Electron Microscopy, 2-D and 1-D geochemical elemental mapping and palaeolimnological and palaeoecological analyses to generate models for the formation of the laminations and their relationship to measured climate change. Building on existing swamp and lake records held by the project supervisors, the candidate will utilise biomarker (leaf wax hydrogen isotopes) records to establish a suit of hydroclimate records with which to disentangle local from regional changes in tropical Pacific climate.
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the School of Geography & Environmental Science. Specific training will include:
- SEM analyses (OES)
- 2-D geochemical elemental mapping (OES)
- Palaeolimnological, palaeoecological and sedimentological analyses (SOGES/RHUL)
- Biomarker analyses (OES/SOGES)
- Statistical analyses on palaeoenvironmental data, notably time series analyses (SOGES).
Brown et al. 2020. South Pacific Convergence Zone dynamics, variability and impacts in a changing climate. Nature Reviews – Earth and Environment https://doi.org/10.1038/s43017-020-0078-2.
Ladd et al. 2021. Leaf Wax Hydrogen Isotope s as a Hydroclimate Proxy in the Tropical Pacific. J. Geophys. Res. Biogeosciences 126, e2020JG005891. doi:10.1029/2020jg005891
Sear et al. 2020. Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought. Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought. Proc. Natl. Acad. Sci. U. S. A. 117, 8813–8819. doi:10.1073/pnas.1920975117