Catastrophic change to Earth’s magnetic field

Project Rationale:

Earth’s magnetic field provides a protective shield from harmful effects of the solar wind, but field strength and behaviour are constantly changing. Even a modestly weakened magnetic field poses a serious threat to the satellite and aviation technology and electrical infrastructure that underpin modern society. Alarmingly, geological records spanning the last few hundred thousand years reveal spectacular geomagnetic excursion events during which the field intensity drops to only a few percent of the present level while field direction temporarily reverses for a few centuries or so [2, 3].

These excursions have been observed in magnetic records from volcanic lavas, marine/lake sediments, wind-blown dust accumulations and cave deposits, and in chemical records from ice cores and sediments showing dramatically increased cosmic radiation. Yet we do not understand the cause or the consequences of these events. Data available for even the best-documented excursion (which occurred ~41 thousand years ago) is insufficient to answer basic questions such as: What happens to the structure of geomagnetic field during an excursion? Does it maintain a mainly dipolar structure (like a bar magnet) or does it become more complex? Do magnetic field excursions start and end synchronously around the globe?

Methodology:

This project will take advantage of a novel instrument, the SQUID Microscope [1], recently developed in Japan, and it will build upon existing collaborations between a team of UK and Japanese scientists. You will combine novel and traditional methods to make a step change in the resolution of palaeomagnetic records achievable from sediment archives to tackle fundamental questions on field behaviour. Using a selected set of deep sea sediment sequences from the North and South Atlantic Ocean and Japanese lake sediments that contain geomagnetic excursions, you will: (1) collect and assemble continuous paleomagnetic records at ultra-high resolution (e.g. every 100 micron) through analysis of continuous sediment thin section samples on a SQUID Microscope; (2) reconstruct high-resolution traditional palaeomagnetic directional and intensity records on superconducting rock magnetometers using both continuous and cut sediment samples; and (3) acquire high-resolution oxygen isotope records and x-ray fluorescence (XRF) core scan data on the sediment cores. These data will be combined for the first time to reconstruct and exploit field behaviours at an unprecedented resolution for accurately dated/correlated records from different world locations, providing new understanding of the structure and spatial variability of the Earth’s magnetic field over the geomagnetic excursions.

Training:

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted in the School of Ocean and Earth Science. Specific training will include:

● Sampling and core analysis at repositories in Europe and/or Japan and work in the laboratories of Japanese collaborators
● High-precision age dating of marine and lake sediments
● Chemical analysis and imaging of sediment cores
● Palaeomagnetic and environmental magnetic analysis of sedimentary archives
● Managing and processing research data and advanced quantitative analysis techniques such as time-series analysis and field modelling
● Correlation, integration, and interpretation of multiple datasets for geomagnetic and environmental reconstructions
● Participation of international scientific meetings to present project results