Utilising mantle seismic structure to constrain mantle circulation and upwellings

Project Background
Earthquakes, volcanoes and mountains all result from the dynamic Earth, driven by mantle convection. This fundamental process that underlies all these very important phenomena is very poorly understood. The great advances in imaging the mantle’s seismic structure over the past few years provide powerful constraints on the dynamics. Mantle convection modellers can now utilise these constraints using mantle circulation models (MCMs). These MCMs predict the internal thermal and compositional structure. By using advanced mineralogy the present-day predictions of temperature and composition can be converted to seismic structure which can be compared with the seismic models. This includes both the radial and lateral structure, as well as the topography on mantle discontinuities, of these seismic models.

Project Aims and Methods
The project aims to constrain the mantle’s dynamics, composition and thermal structure. The student will do this by utilising mantle circulation models (MCMs) (Price et al, 2019; van Heck et al. 2016; Barry et al., 2016; Price and Davies, 2018), which are numerical mantle convection models driven with a surface velocity boundary condition provided by plate motion history (e.g. Müller et al., 2019). These are global spherical models which must be investigated using high performance computing. The resulting present-day composition and thermal structure predicted by the MCMs can be converted to a seismic structure by using thermodynamic mineralogy databases (e.g. Stixrude and Lithgow-Bertelloni, 2011) which give a rigorous framework for incorporating all the relevant mineralogy research. In particular the student will look at the combination of both lateral and radial seismic variations, including the topography of mantle seismic discontinuities. Radial seismic models (Cobden et al., 2009) are very well constrained but have not been explained within the context of global dynamic models. Equally, while lateral variations in seismic tomography studies have been compared with the outputs of MCMs (e.g. Davies et al., 2012) they did not also consider radial models. Further constraints will be provided by observations of the topography of mantle seismic discontinuities at around 410 and 660 km depth (Cammarano and Romanowicz, 2007). There is flexibility in deciding which parameters and variations to investigate in the MCMs; and also which seismic data and mineralogy databases to bring to bear. These give the student the chance to design large elements of the project and choose the research direction. This is a very timely project, given the recent advances in MCMs (thermo-composition), mineralogical experiments and computational toolkits (e.g. ENKI), and seismic studies, and will have a big impact in Earth sciences.

Candidate Requirements
The candidate would ideally have a background either in the methods of modelling or deep Earth processes. The student would also need to have a desire to develop numerical modelling skills and relish the prospect of interacting with high performance computing, and multiple disciplines (geodynamics, mineralogy, seismology). The student could therefore come from a broad range of discipline backgrounds, including for example geophysics, mathematics, physics, engineering, geology, or computing.

Training
The student will learn about the fields of mantle dynamics, mineralogy and seismology. This project will provide ample opportunities to develop high-level skills in computing, programming, numerical modelling and high-performance computing, e.g. using the National Supercomputer ARCHER 2. The student will also have access to a very wide range of University and NERC GW4 DTP provisioned courses which will further enhance research and transferable skills. The student would be expected to attend at least one international conference, e.g. AGU in San Francisco; and visit expert colleagues in the UK associated with the linked MC2 NERC Large Grant project.

Applicants should have (at least) a first or upper second class honours degree in an appropriate subject and preferably a relevant MSc or MRes qualification.