Ice core records of past major volcanic eruptions and their climatic response

Overview

The history of volcanic eruptions is challenging to reconstruct because the geological record of eruptions is often incomplete. Sulfate layers in polar ice cores provide a high-resolution and continuous record of global volcanism through time (e.g. Gao et al., 2008; Sigl et al. 2015). The study of these sulfate layers can provide important insights into the frequency and climatic forcing of volcanic eruptions. In particular, multiple sulfur isotope analyses can be used to identify if the ice core sulfate was formed in the stratosphere, thus providing a means to distinguish large tropical eruptions from local eruptions (e.g. Baroni et al., 2007;2008; Burke et al., 2019). Furthermore recent work (Lin et al 2018) suggests that there is an altitude dependence of Δ33S in stratospheric sulfate, which if true would provide a means of constraining the plume height of past volcanic eruptions.
Although these isotope methods have been applied to eruptions that occurred over the last 2000 years, many major eruptions over the past 100,000 years have yet to be investigated. These techniques have recently been applied to the Toba super eruption (Crick et al., 2021), thus illustrating their utility further back in the ice core record. This PhD project will target some of the Late Quaternary’s largest volcanic eruptions (such as the Oranui eruption of the Taupo volcano in New Zealand) to determine their climate forcing potential. Combining multiple sulfur isotopes with insights from plume and aerosol modelling with project partners and co-supervisors will offer new perspectives on these eruptions and their climatic impacts.

Methodology

Ice cores will be sampled from repositories in Grenoble and Copenhagen. Sulfate concentration will be measured by IC at the University of St Andrews and sulfur isotopes will be measured by MC-ICP-MS at the University of St Andrews in the STAiG laboratories. There is the opportunity to develop new analytical techniques for measuring 36S by state of the art collision cell MC-ICP-MS, however the PhD will not require this method development as all samples can be measured by existing methods. Co-supervisor Lauren Marshall will provide model output from climate simulations using the UK Earth System Model (UKESM) and will train the student in interpreting results.

Project Timeline

Year 1

Literature review, ice core sampling, training in clean laboratory methods and mass spectrometry at the STAiG laboratory. Method development on new state of the art collision cell MC-ICP-MS.

Year 2

Ice core sulfate concentration by ion chromatography and Δ33S isotope measurements by MC-ICP-MS at St Andrews. Research visit to Durham for training in interpreting model output. Analysis of model results. Write up initial results into paper. Present results at national conference (e.g. VMSG annual meeting or GGRIP meeting).

Year 3

Finish remaining ice core sample measurements, finalize data sets, prepare written manuscripts. Present results at international conference (e.g. EGU, VICS workshop)

Year 3.5

Finish writing thesis.

Training
& Skills

The student will gain specific training in geochemical laboratory techniques including ion chromatography, mass spectrometry, and clean lab chemistry, as well as training and expertise in volcanology, climate science, atmospheric chemistry, and isotope geochemistry. The student will be trained and work with MC-ICP-MS and a new state of the art collision cell MC-ICP-MS. The student will also be trained in computer programming (e.g. Matlab, Python, or R) to process and analyse data and model results. Furthermore, over the course of the PhD the student will gain transferable skills such as scientific writing, statistics and data analysis, and problem-solving, as well as time management and working towards a long-term goal.

References & further reading

• Baroni, M. et al., 2008.. Journal of Geophysical Research, 113(D20), p.D20112.
• Baroni, M. et al., 2007. Science, 315(5808), pp.84–87.
• Burke, A et al., 2019. EPSL , 521, pp113-119.
• Crick, L et al., 2021. Climate of the Past, 17, pp. 2119–2137.
• Gao, C., Robock, A. & Ammann, C., 2008. Journal of Geophysical Research, 113(D23), p.D23111.
• Lin, M. et al. (2018). Proceedings of the National Academy of Sciences, 115(34), 8541–8546. http://doi.org/10.1073/pnas.1803420115
• Sigl, M. et al., 2015. Nature, 523(7562), pp.543–549.

Further Information

For further information contact:

Dr Andrea Burke
ab276@st-andrews.ac.uk

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