- Unravel Last Interglacial to present ocean climate history from the remote Eparses Islands (Scattered Islands) in the western Indian Ocean, with cutting edge coral core geochemistry spanning several decades per time slice
- Undertake innovative climate and geochemical proxy data analysis and develop paleoclimate reconstructions of temperature, hydroclimate and nutrient dynamics for the southern Mozambique Channel feeding the globally important Agulhas Current
- Bring the palaeoclimate data from past warm and cold stages into context with anthropogenic climate change and compare with SW Madagascar coral records.
Understanding the role of ocean circulation in shaping the patterns of ocean warming, salinity and nutrient transport remain key to predicting global and regional climate change, ocean nutrient cycling and ecosystem responses. Western boundary currents are vital bottlenecks modulating global heat and freshwater distribution, as well as nutrient dynamics. Currently it is not known to what extent anthropogenic warming and associated changes in the hydrological cycle and nutrient dynamics exceed natural variability linked to seasonal, interannual and (multi)decadal Indo-Pacific and Atlantic climate variability. In particular, we have little knowledge if anthropogenic climate change contributed to amplifying or dampening heat and freshwater transport along the southern Indian Ocean currents (South Equatorial Current; Mozambique Channel eddies) feeding the Agulhas Current (AC), one of the most powerful western boundary currents on the planet. Ultimately, the AC will feed into the Atlantic Meridional Overturning Circulation (AMOC) via Agulhas leakage into the South Atlantic and therefore is a critical joke point in the global thermohaline circulation affecting global climate (Beal et al., 2011; de Ruijter et al., 2004).
Given the importance of vigorous, eddy-driven western boundary currents for nutrient transport between the shelf and open ocean in the Mozambique Channel (MC) and AC sustaining highly productive and highly valuable fishing grounds (e.g. Tuna; Chassot et al., 2019), it is of paramount importance to study the long-term trends and the full suite of variability in nutrient dynamics coupled to thermohaline properties under varying climate background conditions influenced by orbital cycles (present to past climate states).
Our proposed study, therefore, will address this key knowledge gap by developing modern (~1850-2019 A.D.) and fossil (Last Millennium to Last Interglacial) coral paleoclimate records at unprecedented sub-monthly resolution obtained from key sites within the tropical, low-latitude MC inflow and the southern MC outflow feeding the globally important AC (Fig. 1). We will use state-of-the-art analytical approaches to develop coral geochemical records which will be paired with climate model-derived (Kiel Climate Model) and observational estimates to unravel the climate and ocean dynamics influencing the MC-AC western boundary flow on a variety of society-relevant time scales.
Sea surface temperatures (austral summer; map available from http://apdrc.soest.hawaii.edu/data) across the southwestern Indian Ocean with the major ocean currents forming part of the global surface thermohaline circulation route: SEC: South Equatorial Current, EMC: East Madagascar Current, NEMC: North East Madagascar Current, AC: Agulhas Current, ACR: Agulhas Current return flow, MCE: Mozambique Channel Eddies. The Europa and Glorieuses archipelago coral locations and the region of dense SST observations for the Agulhas Current are indicated. The region of Agulhas ring shedding (AR) indicates Indian-Atlantic ocean exchange of heat and salt thought to influence the AMOC. Coral data available for regional comparisons are indicated (JdN: Juan de Nova; MAY: Mayotte, Zinke et al., 2008; Ifaty, SW Madagascar, Zinke et al., 2014).
Figure 1 – Sea surface temperatures (austral summer; map from http://apdrc.soest.hawaii.edu/data) across the southwestern Indian Ocean with the major ocean currents forming part of the global surface thermohaline circulation route indicated: SEC: South Equatorial Current, EMC: East Madagascar Current, NEMC: North East Madagascar Current, AC: Agulhas Current, ACR: Agulhas Current return flow, MCE: Mozambique Channel Eddies. The Europa and Glorieuses archipelago coral locations (large yellow dot) and the region of dense SST observations (rectangular box) for the Agulhas Current are indicated. The region of Agulhas ring shedding (AR) indicates Indian-Atlantic ocean exchange of heat and salt thought to influence the AMOC. Coral data available for regional comparisons are indicated by a small yellow dot (JdN: Juan de Nova; MAY: Mayotte, Zinke et al., 2008; Ifaty, SW Madagascar, Zinke et al., 2014).
HostUniversity of Leicester
- Climate and Environmental Sustainability
- Organisms and Ecosystems
Dr. Arnoud Boom, University of Leicester ([email protected])
Prof. Jens Zinke, University of Leicester ([email protected])
Kenneth Johnson, NHM London, UK ([email protected])
Dr. Mireille Guillaume, MNHN Paris, France ([email protected])
Prof. Miria m Pfeiffer, Kiel University, Germany ([email protected])
Prof. Birgit Schneider, Kiel University, Germany ([email protected])
Prof. Henrich Bruggemann, University of La Reunion, France ([email protected])
Dr. Alan Foreman, Max Planck Institute, Mainz, Germany ([email protected])
We have drilled living massive Porites corals and Last Millenium/Holocene/Last Interglacial boulders from storm deposits during a research cruise with the vessel Marion Dufresne II in April 2019. Several long, modern coral cores from living (>100 year) and fossil corals (>30 years) at exceptional quality are available for this study through collaboration with the University of La Reunion and the Natural History Museum in Paris. Absolute chronologies were established from U/Th dating at the University of Oxford. Yearly growth changes will be revealed from coral slabs by layer counting (CT-scanning NHM London). Diagenetic screening with XRD and SEM will be done in Leicester to ensure best preservation. Corals will be sampled at higher the monthly resolution using a MicroMill sampler.
Proxies for sea surface temperature and salinity will be obtained at the University of Leicester by trace element (Sr/Ca etc., ICP-MS; Zinke et al., 2019) and isotope (δ18O, δ13C) analyses, while nutrient cycling (skeletal bound organic δ15N; Wang et al., 2015; Duprey et al., 2017) will be done at Max-Planck in Mainz (Germany) and Leicester. All sampling will provide monthly-resolved reconstructions.
Training and skills
Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2 – provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.
The student will become proficient in experimental design and protocols, in use of sophisticated analytical equipment including inductively-coupled-plasma mass spectrometry, stable isotopes, XRD, X-ray (mostly at the University of Leicester) and CT-scanning (NHM London). This combination of innovative methods and state-of-the-art analytical equipment will provide you with a truly unique set of skills that will be attractive to both industrial and academic employers.
Partners and collaboration
There is an active research group at the Natural History Museum using micro Computed Tomography to extract ecological information from reef-coral skeletons. These data include annual extension and calcification rates of colonies as well as the occurrence of past growth anomalies caused by stress events such as coral bleaching. For the proposed project the sampled coral colonies will be scanned using a Nikon Metrology HMX ST 225 to extract growth data and correlate with results of geochemical analyses determine how coral growth has responded to variation in historical environmental conditions since the Last Interglacial.
If you wish to apply to the project, applications should include:
- A CENTA application form, downloadable from: CENTA application
- A CV with the names of at least two referees (preferably three and who can comment on your academic abilities)
- Submit your application and complete the host institution application process via: https://le.ac.uk/study/research-degrees/funded-opportunities/centa-phd-studentships Please quote CENTA2-SGGE5-BOOM when completing the application form.
Applications to be received by the end of the day on Wednesday 11th January 2023.
Get acquainted with the research methods and corals as climate archives through intensive literature study. Determine the sampling strategy for the cores based on CT/X-ray. Use of milling machine to obtain powders from the cores. Check core parts for diagenesis with XRD and SEM plus thin sections. Perform test measurements in stable isotope and ICP-MS labs before starting with real samples. Commence analysis of first real samples end of year 1. Organise 1 field trip for fossil collection and water sampling to characterize present-day seawater values of nitrogen isotopes, Sr/Ca and δ18O for calibration of geochemical signatures.
Continue the sampling and geochemical data acquisition on selected dates. Collect orbital paramters for past climate stages and compare with present instrumental climate data and perform initial correlation/regression analysis. Get acquainted with data analysis toolkits (R, Matlab, Python, knmi climate explorer). Aim for first presentation of initial data at national or international conference mid-end year 2.
Application of data analysis toolkits to entire dataset. Interpretation of geochemical data and working out climate and environmental drivers at regional and global scale. Synthesis of data for key time slices. Peer-reviewed publications and conference presentations will be part of the schedule from year 2 onwards, including the opportunity to present at international meetings.
Beal, L. M., et al. (2011) Nature, 472, 429-436
Biastoch, A., et al. (2009) Nature, 462, 495–498
De Ruijter, W. P. M. et al. (2004) Deep-Sea Research Part I, 51, 383-400
Duprey, N. et al. (2017) Marine Poll. Bull., 120
Chassot et al. (2019) Rev Fish Biol Fisheries, doi:10.1007/s11160-019-09569-9
Wang, X.T. et al. (2015) Geoch, Cosmoc. Acta, 148, 179-190
Zinke et al. (2008) Geophys. Res. Let., 35, L23707
Zinke, J., et al. (2014a) Sci. Reports, 4, 4393
Zinke et al. (2019) Biogeosciences, 16, 695-712
The coral core samples for the project have already been collected and samples have been shipped to Leicester. The project does not rely on fieldwork, 1 planned field trip could be postponed. All analyses planned for this project can be done at our laboratories at the University of Leicester (UoL), NHM London and through an established collaboration with Max-Planck in Mainz and University of Kiel (Germany). UoL has protocols established to ensure a safe working environment should Covid-19 restrictions change. The project can go ahead even with further restrictions on travel due to Covid-19.