Improving Paleointensity: A key to understanding the past and future of Earth’s magnetic field

The strength of Earth’s ancient magnetic field (paleointensity) is a uniquely powerful probe of the evolution of the planet on which we live, allowing constraint on Earth’s dynamics and thermal history. Identifying good paleointensity results is a frontier in Earth science magnetism and a lack of consensus is a hindrance in understanding important changes in Earth’s magnetic field. For example, direct observations of Earth’s magnetic field strength have shown the dipole field (the main north-south component) has been steadily weakening for at least 200 year. The decay of the dipole is intimately related to a growing weak spot known as the South Atlantic Anomaly – a region where satellites are exposed to higher solar wind radiation and can experience failure. Understanding the future of the field is important for understanding how the protection provided by Earth’s magnetic field will change, but to understand the future we need longer records of variation in the past. Attempts to reconstruct the longevity of dipole decay have varied widely in their estimates. This is mainly due to large differences in what data are viewed as being reliable. This project will develop a new and innovative method for assessing the reliability of paleointensity data and determine for how long our magnetic shield has been in decline.

Project Summary:
There are many reasons why paleointensity results can be unreliable, but the role of chemical alteration when the samples are heated in the lab or in nature is the most poorly understood.
The candidate will start by using the wide range of magnetic, microscopy and geochemical tools available at Liverpool to explore how chemical alteration impacts paleointensity data and develop a first-order model that allows this to be simulated. This will use a wide range of geological and archeological materials from collections held in Liverpool and from collaborators in Europe. This new alteration model will be incorporated with existing models to establish a tool to predict paleointensity results. The paleointensity predictor will be used to determine what results are accurate and reliable enough to reconstruct past variations in the strength of the geomagnetic field. The tool will be calibrated to data from recent times, when the field strength is known. It will then be applied to older time periods, initially focusing on resolving different models of the longevity of recent dipole decay, but this new tool has the potential to be applied to any period in geological history. The project will be split into equal thirds between experimentally exploring alteration, developing the paleointensity predicting model, and then applying it to resolve recent dipole behavior. This rough plan will be flexible to the student’s skills and interests to pursue side projects.

This project would suit a geophysics graduate who is keen to learn both lab based experiments and numerical simulations, working towards bridging the gap between them. The student will complete a skills audit at the onset of the project, which will identify the aspects of the project for which specialist training need be provided.