Lithium isotopes in foraminifera: a new proxy for the ocean carbonate system?

Rationale: 

The lithium (Li) isotope composition of tiny shells of marine plankton (foraminifera) preserved in sediment cores is traditionally thought to record past variations in the Li isotopic composition of seawater (e.g. [1]). However, it is becoming increasingly apparent that foraminiferal Li isotopes can also be indirectly affected by the concentration of carbonate dissolved in seawater (e.g. [2]). This presents both a challenge and an opportunity, because knowledge of how both parameters (seawater Li isotopic composition and seawater carbonate ion concentration) changed in the past provides critical information on, respectively, rates of continental weathering and ocean pH. This information in turn is essential for understanding how and why Earth’s climate and atmospheric CO2 have changed in the past and for predicting how they may change in the future [3].

This project will explore the lithium isotope and other complementary elemental and isotope systems in foraminifera through investigations focused on field and laboratory studies. This work will generate a mechanistic understanding of the factors that control the Li isotope composition of foraminiferal calcite that provides a robust framework for better understanding the Earth’s climate system and the causes of natural climate variations.

Methodology: 

This PhD studentship is supported by a fund set up to commemorate the work of Prof. Harry Elderfield (https://en.wikipedia.org/wiki/Harry_Elderfield) that will enable the student will tackle this problem in a number of different that will enable the student will tackle this problem in a number of different ways. They will first travel to Eilat in Israel to culture foraminifera under different carbonate ion concentrations to parameterize the relationship between lithium isotopes and seawater carbonate. They will also carry out some controlled carbonate precipitation experiments in the laboratory at the National Oceanography Centre to nail down the isotope fractionation that occurs on Li incorporation into calcite and its dependence on the seawater carbonate system and other environmental variables. Armed with this information, the student will then reconstruct environmental conditions at several locations and for different time periods, including the Last Glacial Maximum. These data will be supplemented by analysis of other elemental and isotope systems (including boron isotopes) and also compared to existing data to better constrain the environmental control on Li isotope incorporation.

Location: 
University of Southampton and National Oceanography Centre Southampton
Training: 

All doctoral candidates will enrol in the Graduate School of NOCS (GSNOCS), where they will receive specialist training in oral and written presentation skills, have the opportunity to participate in teaching activities, and have access to a full range of research and generic training opportunities. GSNOCS attracts students from all over the world and from all science and engineering backgrounds. There are currently around 200 full- and part-time PhD students enrolled (~60% UK and 40% EU & overseas).  Specific training will include:

      i.        Practical training in culturing foraminifera in the field. This will take place during fieldwork in Eilat, Israel.

     ii.        Training in state-of-the-art methodologies for analysis of stable isotope ratios by laser ablation and solution multicollector inductively coupled plasma mass spectrometry.

    iii.        Training in conducting carbonate precipitation experiments under carefully controlled conditions.

    iv.        Training in processing of marine sediments samples and identification and cleaning of foraminifera shells.

The student will, along with their supervisors, also organize and host a 1-day scientific meeting to commemorate the legacy of Prof. Harry Elderfield, during the course of the studentship.

Eligibility & Funding Details: 

To find information on ‘how to apply’ for a GSNOCS PhD project please click the following link: http://noc.ac.uk/education/gsnocs/how-apply

To apply, please click the following link: https://studentrecords.soton.ac.uk/BNNRPROD/bzsksrch.P_Login?pos=8296&term=201920

General enquiries should be directed to the GSNOCS Admissions Team on gsnocs@southampton.ac.uk.

 

Background Reading: 

[1] Misra S. and Froelich P.N. (2012) Lithium isotope history of Cenozoic seawater: Changes in silicate weathering and reverse weathering. Science 355, 818-823.

[2] Roberts J., Kaczmarek K., Langer G., Skinner L.C., Bijma J., Bradbury H., Turchyn A.V., Lamy F., Misra S. (2018) Lithium isotope composition of benthic foraminifera: a new proxy for paleo-pH reconstruction. Geochimica et Cosmochimica Acta 236, 336-350.

[3] Elderfield H. (2002) Carbonate mysteries. Science 296, 1618-1621.

Contact Email: 

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