2024-L15 Late Miocene thermal gradients in the equatorial Pacific during prolonged El Niño- and La Niña-like states

Project highlights

Establish Late Miocene equatorial Pacific thermal gradients during shifts from El Niño-like and La Niña-like conditions
Test changes in sensitivity of sea surface temperatures to astronomical forcing during El Niño- versus La Niña-like conditions.
Investigate impact of prolonged warm periods on foraminiferal ecology

Overview

Late Miocene (11.63-5.333 Ma) climate was characterised by warmer temperatures and CO2, similar to the 4°C warming and CO2 levels predicted by the IPCC for the year 2100. There has been an ongoing question about whether or not permanent El Niño-like conditions existed during the Late Miocene, with the equatorial Pacific characterised by warm waters spread across the entire region. As the modern El Niño causes significant global climate anomalies, understanding the potential presence and impacts of permanent El Niño-like conditions in the past is important.

There are currently three main hypotheses about which conditions dominated the equatorial Pacific during the Late Miocene: 1) a Late Miocene permanent El Niño-like state (e.g., Ravelo et al., 2014), 2) alternating El Niño-like (9.6-6.5 Ma) and La Niña-like (6.5-6.1 Ma) states (e.g., Nathan and Leckie, 2009; Drury et al., 2018), or 3) modern thermal gradients since ~12 Ma (e.g., Zhang et al., 2014). However, the lack of high-resolution records in the Western Pacific Warm Pool (WPWP) was a hurdle to resolving which hypothesis was more likely. A recent project generated new high-resolution stable oxygen (δ18O) isotope data in the WPWP (Drury, MIONIÑO, 2019-2022), but independent temperature records are nonetheless needed to establish E-W equatorial Pacific temperature gradients, as foraminiferal δ18O is also influenced seawater δ18O changes (e.g., global ice volume, salinity), as well as temperature.

This PhD project would focus on generating high-resolution sea surface and thermocline temperature records in the WPWP using planktonic foraminiferal Mg/Ca analysis paired with clumped isotope (Δ47) thermometry on coccolith-rich fine fraction sediment. This would make it possible to reconstruct the WPWP thermocline structure, as well as E-W thermal gradients, to understand the thermal impact of alternations between prolonged El Niño-like and La Niña-like conditions. As the records will be high-resolution, it will make it possible to test whether the sensitivity to astronomical forcing changes between these climate states. The impact of these different climate states and associated thermal shifts on the biosphere will be investigated using multi-species planktonic foraminiferal geochemistry records.

Host

University of Leicester

Theme

Climate and Environmental Sustainability
Organisms and Ecosystems

Supervisors

Project investigator

Dr Anna Joy Drury, University of Leicester, [email protected]

Co-investigators

Dr Tom Dunkley Jones, University of Birmingham, [email protected]

Professor Jens Zinke, University of Leicester, [email protected]

How to apply

Each host has a slightly different application process.
Find out how to apply for this studentship.
All applications must include the CENTA application form.
Choose your application route

Methodology

The proposed PhD project will focus on generating Mg/Ca major trace element analysis of planktonic mixed layer and thermocline foraminifera to reconstruct upper water column temperatures in the WPWP, using material recovered by the International Ocean Discovery Program (IODP). Clumped isotope Δ47 thermometry on coccolith-rich fine fraction will help constrain long-term temperature changes that may be impacted by changes in seawater Mg/Ca concentration. Scanning electron microscopy to establish specimen preservation and the composition of the isolated sediment fractions. Spectral analysis techniques on the new data will be used to test for any sensitivity changes of sea surface temperatures to astronomical forcing during the changing climate states. Multi-species δ18O and δ13C analyses will be used to trace links between ecological and environmental changes during prolonged warm intervals.

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 prospective student will become familiar with key Late Miocene planktonic foraminifera. They will be trained in preparation and analysis of foraminifera for major trace element analysis and stable oxygen and carbon isotope analysis using the IRMS and ICP-MS facilities at the University of Leicester. The student will isolate the coccolith-dominated fraction for clumped isotope Δ47 analysis. The project utilises IODP material and associated data, so the student will be introduced to this international programme, as well as become part of a collaborative network associated with the original IODP expedition and the previous MIONIÑO project (https://www.ucl.ac.uk/earth-sciences/research/research-groups/micropalaeontology/research/mionino).

Partners and collaboration

This project builds on the results from several recently completed grants (Horizon2020 MSCA MIONIÑO fellowship; DFG IODP Priority Programme Project) developed collaboratively between the PI and researchers at UCL (Professor Bridget Wade, Professor Paul Pearson), MARUM, University of Bremen (Dr Thomas Westerhold) and UCSC (Professor Ana-Christina Ravelo). The prospective student will have the opportunity to integrate their results with the data from these studies and discuss their results with collaborators. In addition, the student will work closely with Dr Tom Dunkley Jones (University of Birmingham) on the isolation of coccolith-rich fine fraction for clumped isotope analysis.

Further details

Further details on how to contact the supervisor for this project and how to apply for this project can be found here:

For any enquiries related to this project please contact Dr Anna Joy Drury, [email protected].

To apply to this project:

You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2024.
You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.
Please submit your application and complete the host institution application process via: https://le.ac.uk/study/research-degrees/funded-opportunities/centa-phd-studentships. Please scroll to the bottom of the page and click on the “Apply for NERC CENTA Studentship” button. Your CV can uploaded to the Experience section of the online form, the CENTA application form 2024 can be uploaded to the Personal Statement section of the online form. Please quote CENTA 2024-L15-CENTA2-SGGE8-DRUR  when completing the application form.

Applications must be submitted by 23:59 GMT on Wednesday 10th January 2024.

Possible timeline

Year 1

Literature search and familiarisation with existing datasets available at the target site. The student will be trained in the cleaning process for foraminiferal trace element analysis and start analysis of the foraminiferal trace element geochemistry. The students can also pick multispecies planktonic foraminifera for stable isotope analyses.

Year 2

The student will finish the trace element time series analyses. They student can familiarise themselves with spectral analysis techniques using existing high-resolution X-ray fluorescence (XRF), core image tracks and foraminiferal stable isotope data, and apply it to the new dataset they’ve generated (potential manuscript 1). The student can run the multispecies stable isotope and trace element analyses to see the impact of environmental changes on the ecology of planktonic foraminfera (potential manuscript 2).

Year 3

Based on their trace element time series, the student can determine which samples to target for fine fraction clumped isotope thermometry. The student will be trained in how to isolate a coccolith-rich size fraction, and use this material for clumped isotope analysis to look at long-term temperature evolution and reconstruct changes in the Mg/Ca composition of seawater (potential manuscript 3). Thesis writing, incorporating the three manuscripts/manuscript drafts.