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PhD topic: High precision surface exposure dating

Supervisory Team

  • Are you interested in joining a NERC-funded team of scientists pushing the limits of metrology and geochronology?

  • Does technology excite you?

  • Would you like to learn how to operate high-energy particle accelerators?

  • Do you have experience in analytical chemistry and/or physics?

If the answers are Yes, read on

Project Overview

One of the clearest indicators of global warming is the shrinking of terrestrial ice masses and the marked reduction of sea ice in the Arctic, where atmospheric warming is most pronounced. Melting of sea ice does not contribute to sea level rise, but meltwater from land-based glaciers and ice caps is a major contributor to sea level rise. How fast will glaciers and ice caps melt? Will they disappear in decades, adding all of their water rapidly to the oceans, or will the melting occur over a longer time span.

 

This project will determine how fast ice caps can melt by quantifying the collapse of the ice cap that existed in Scotland about 12000 years ago and disappeared at a time when temperatures rose by about 7°C, similar to the temperature rise predicted for the Arctic by 2100.

By measuring how quickly the ice cap disappeared we will learn how fast present day equivalent sized ice masses subjected to similar warming could disappear, thus providing data needed for sea level rise models to make more informed predictions.

 

To quantify how fast the Scottish ice cap collapsed we need to be able to determine the rate of change of the former ice mass. We will use surface exposure dating with the cosmogenic nuclides 10Be and 26Al produced in the mineral quartz by secondary cosmic rays, that is, when rock is exposed to the sky. Surface exposure dating is the only technique available to directly date when landforms become exposed as ice melts. You will measure the concentration of these nuclides in glacially abraded and plucked rock located at the maximum, intermediate and minimum extent of the ice cap. You will determine when the ice disappeared from the sample sites and establish the retreat rate which will be integrated with independently dated climate proxy archives to look for causal relationships.

Methodology

To be able to test the hypothesised rapid collapse of the Scottish ice cap we first need to improve the surface exposure dating technique from the current routine 2-3% measurement precision for 10Be and 26Al in quartz to 1% or better. Analytical improvements to accelerator mass spectrometry (AMS) currently used to measure 10Be and 26Al will allow us to resolve the rate of ice cap collapse. However, there are some questions for which AMS is unlikely to provide the necessary precision. To resolve if the decline of the ice cap was steady or episodic requires the development of an entirely new methodology. Positive ion mass spectrometry (PIMS) invented and pioneered at the Scottish Universities Environmental Research Centre (SUERC). Pushing the boundaries of conventional AMS and developing 26Al PIMS potentially leads to a paradigm shift in how Earth and Environmental scientists determine the rate of natural processes and the age of landforms with cosmogenic nuclides.

Timeline

Year 1:

Refining key research questions and establishing hypotheses; sample site selection; fieldwork; training in core geochemistry, accelerator mass spectrometry skills, and PIMS skills; testing AMS ion source operation using different sample matrices and AMS cathode configurations; PhD progression presentation.

Year 2:

AMS and PIMS ion source optimisation; field sample preparation; data analysis; statistical modelling; presentation at national conference.

Year 3:

Further data analysis; lead authorship of key manuscript(s); presentation at international conference (e.g. AGU, EGU); thesis preparation and write-up; thesis submission for examination.

 

Training & Skills

This is a unique PhD opportunity for an analytically minded candidate, offering direct access to globally unique technologies and you will gain specialist and complementary interdisciplinary skills. Specifically, training will be provided in field sampling for surface exposure dating; laboratory sample preparation; cosmogenic-nuclide analysis by AMS and PIMS; data reduction; numerical data interpretation and statistical modelling. The successful candidate will also receive training in oral and poster presentation skills & paper, grant application and thesis writing.

 

This project will provide you with a unique skill set in surface exposure dating, analytical chemistry, AMS and PIMS analytical techniques, and glacial geomorphology.

 

References & Further Reading

Balco, G. 2011. Contributions and unrealized potential contributions of cosmogenic-nuclide exposure dating to glacier chronology 1990-2010. Quaternary Science Reviews, 20: 3-27.

 

Dunai, T. 2010. Cosmogenic Nuclides: Principles, Concepts and Applications in the Earth Surface Sciences. Cambridge University Press, Cambridge, UK.

 

Further Information

For further information, or informal enquiries, contact Dr Richard Shanks richard.shanks@glasgow.ac.uk

or Dr Derek Fabel derek.fabel@glasgow.ac.uk