The Pacific is the largest ocean basin and plays the most important role for water cycle changes on a global scale. To date, our knowledge of the Pacific Ocean’s role in the water cycle and their influence on climate relies on short and sparse instrumental observations of rainfall, evaporation and salinity, along with ocean model simulations that persistently exhibit biases in replicating current observed patterns. The largest uncertainty in instrumental ocean observations stems from the sparseness of sea surface ocean salinity (saltiness) measurements.
These South Pacific Ocean gyres (Fig. 1) are of particular great importance for long-term climate prediction as they contribute to the redistribution of temperature anomalies from the subtropics to the equator influencing water vapour formation for rainfall in the atmosphere above. The South Pacific gyre thereby has the potential to modulate the El Niño Southern Oscillation and decadal-scale variability like the Interdecadal Pacific Oscillation, both of which have major impacts on global climate
Here we will use the geochemical composition of exceptionally long-lived coral archives to provide a unique view of six centuries of ocean salinity change in the southwest Pacific (e.g. Zinke et al., 2023). By combining our palaeoclimatic data with modern observations and models, we will develop a new independent reconstruction of southwest Pacific surface ocean salinity fields, improving our understanding of natural variability and better our estimates of the impact of anthropogenic warming on the hydrological cycle.
Figure 1. Our coral core locations (marked by symbols) are strategically placed to trace the South Equatorial Current (SEC) flow (thick pink arrows) and the South Pacific Convergence Zone (SPCZ) salinity change from Fiji archipelago into the Coral Sea. North Queensland Current (NQC), East Australian Current (EAC).
This project is not suitable for CASE funding
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The coral cores and part of the coral tissue samples that we propose to study were already collected and dated with densitometry/CT-scanning by the Co-I’s and our partner at no cost to NERC in collaboration with the Australian Institute of Marine Science (PI is Adjunct at AIMS) (DeCarlo et al., 2019; Harrison et al., 2019). We will develop annually resolved proxy records of changes in sea surface temperature (SST: (Sr/Ca; U/Ca; Sr-U; Li/Mg) and salinity (oxygen isotopes) from GBR and central Coral Sea coral cores using Laser Ablation ICP-MS (supported by Foster lab at the Univ. of Southampton) and stable isotope geochemistry (at UoL). We will assess changes in coral health through time by using available coral growth parameters on all cores and how recent 21st century changes sit within the long-term memory of thermal stress across the selected reef systems.
DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.
The PhD student will receive extensive training in ICP-MS and stable isotope geochemistry from established international leaders in the field of coral core geochemistry. The study will include training in statistical data analysis and collaborations with climate scientists from the NCEO. Furthermore, the project will involve collaborations with Australian partners at the Australian Institute of Marine Science (AIMS).
Prof. Gavin Foster is a leader in trace element geochemistry on marine carbonate including foraminifera and corals. Prof. Foster leads an advanced geochemical facility with a variety of instrumentation. He leads an EU Horizon Advanced Grant project with a number of PhDs and postdocs focused on coral skeletal geochemistry.
Our international partners are the Australian Institute of Marine Science (AIMS) in Townsville, Queensland, Australia and the Universidad Autonoma in Mexico. Dr. Neal Cantin is our partner at AIMS, he leads the Australian coral core archive. AIMS is a Government Institution. PI Zinke is an Adjunct Senior Scientists at AIMS and was previously employed by AIMS between 2011-2015. Dr. D’Olivo is a specialist in coral core geochemistry with an emphasis on South Pacific palaeoclimate.
Year 1: Literature study month 1-6, project proposal and literature review as part of 9-month probation report which will feed into Introductory chapter of the thesis; training in geochemistry
Year 2: Analysis of trace elements and stable isotopes at UoL and UoS laboratories; data acquisition and interpretation; familiarize with observational climate data; learn statistical methods; conference presentation of first results; write up results for Data Chapter 1
Year 3: Synthesis of geochemical analytical results; refinement of thermal stress and salinity variability history at the selected core location; climate and oceanographic interpretation; write up results for Data Chapters 2 and 3 focussing on long-term variability and thermal stress events.
Journal:
Calvo E, Marshall JF, Pelejero C et al. (2007) Interdecadal climate variability in the Coral Sea since 1708
A.D. Palaeogeography Palaeoclimatology Palaeoecology 248: 190–201.
D’Olivo JP, et al. (2018) A universal multi-trace element calibration for reconstructing sea surface temperatures from long-lived Porites corals: Removing ‘vital-effects’. Geoch. et Cosmoch. Acta 239, 109–135, https://doi.org/10.1016/j.gca.2018.07.035
D’Olivo et al. (2024) Science Advances 10, eado5107
DeLong et al. (2013) Palaeogeogr. Palaeoclimatol. Palaeoecol. 373, 6–24
Hendy EJ, Gagan MK, Alibert CA et al. (2002) Abrupt decrease in tropical Pacific sea surface salinity at end of Little Ice Age. Science 295: 1511–1514.
Marzonie, M. R. et al. (2022) The effects of marine heatwaves on acute heat tolerance in Corals. Global Change Biology, 1-13, https://onlinelibrary.wiley.com/doi/epdf/10.1111/gcb.16473
Zinke, J et al. (2023) North Flinders Reef (Coral Sea, Australia) Porites sp. corals as a candidate Global Boundary Stratotype Section and Point for the Anthropocene Series. The Anthropocene Review, 1-24, doi:10.1177/20530196221142.
For any enquiries related to this project please contact Prof. Jens Zinke, [email protected].
To apply to this project:
Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026.