We are seeking postdoctoral researchers to work on novel methods of ocean chemistry and atmospheric CO2 reconstruction over the last 100 million years. Candidates should have expertise in paleoclimate and/or low temperature geochemistry, using geochemical analyses and/or biogeochemical modelling. Positions are initially available for two years, with flexible start dates and options for extension for outstanding candidates.

CO2 is invoked to drive some of the most profound changes in Earth’s history, from long-term climate evolution between greenhouse and ice-house worlds, to mass extinctions due to rapid perturbations to the carbon cycle. However CO2 reconstruction beyond the reach of the ice core record remains challenging, limiting our understanding of Earth’s past and insights into its future. This ERC-funded project, led by Dr James Rae, aims to transform our ability to reconstruct ocean chemistry and atmospheric CO2 over the last 100 Million years, using novel archives and approaches, and use these new records to better understand CO2’s role in major environmental change.

This will be achieved by developing new methodologies for the robust application of the boron isotope (11B) pH proxy, coupled with Earth System modelling to reconstruct atmospheric CO2. Substantial progress has been made in the use of the 11B proxy, but a few key uncertainties currently limit the accuracy and precision with which this method can be applied. The most critical is knowledge of the boron isotope composition of seawater (11Bsw), which is required to convert measurements of 11B in carbonates into pH. Secondary constraints on seawater carbonate and major element chemistry are also required for accurate CO2 system determination. Finally, the scope of 11B-based pH reconstructions also remains limited simply by the lack of long-term 11B records. This project will address these challenges, transforming our understanding of pH, CO2, and carbon cycle change over the past 100 Myr.

To reconstruct the boron isotope composition of seawater we will develop a variety of independent new approaches. The first focuses on the composition of evaporites, which have boron isotope compositions close to that of seawater, and have been shown to provide valuable constraints on the evolution of the ocean’s major element composition. However several processes may alter the composition of evaporite forming brines away from that of seawater, and new approaches and analytical techniques are required to constrain these. This work will first ground truth these methods, using lab experiments and work in modern evaporitic settings, before applying them to ancient evaporite deposits. Suitable candidates for this aspect of the project will be comfortable with geochemical modelling, experiments, and analyses, and may have experience in evaporitic environments.

We will also use detailed geochemical measurements on foraminifera and corals to constrain 11Bsw and ocean pH, taking advantage of limits on pH imposed by under-appreciated biomineralisation pathways and ecological niches. Suitable candidates will have worked on foram or coral proxies and biomineralisation, and have strong analytical geochemistry, ideally including in-situ analysis.

With 11BSW constrained, 11B records can be converted to pH and used to constrain CO2. We will create detailed high-quality long-term 11B data from a variety of locations and foram species, and pair this with trace element data and Earth system modelling, to reconstruct the evolution of the ocean-atmosphere CO2 system. Suitable candidates will have a strong understanding of the carbonate system, long term climate evolution, and expertise in foram-based geochemical records and/or Earth system modelling.

Informal enquiries can be addressed to project Principal Investigator Dr James Rae jwbr@st-andrews.ac.uk 

The University is committed to equality for all and has a series of diversity awards (ECU Athena SWAN/Race Charters; Carer Positive; LGBT Charter; and Stonewall - see http://www.st-andrews.ac.uk/hr/edi/diversityawards/. We encourage applications from all members of society.

School of Earth & Environmental Sciences

Salary: £33,199 - £39,609 per annum

Fixed Term: 2 years in the first instance

Start: To be mutually agreed