Stochastic optimisation of absolute geomagnetic palaeointensity determinations
Lead Research Organisation:
University of Liverpool
Department Name: Earth, Ocean and Ecological Sciences
Abstract
I propose to develop a new mathematical tool that will make measurements of the Earth's magnetic field strength in the ancient past much more reliable and efficient. The magnetic field of the Earth extends far into space and is important to humans for many reasons. It is used by us and other species for navigation and it also protects human technology from the 'solar wind' - a stream of high-energy particles emitted by the sun. The interaction of the solar wind with the Earth's magnetic field causes aurorae (the Northern and Southern Lights) and other 'space weather' phenomena. The initiation of a strong, global 'geomagnetic' field more than three billion years ago may have been a crucial factor in allowing the first life on Earth to appear. Before then, the atmosphere might not have been able to form because of continual erosion by the solar wind. The importance of the Earth's magnetic field to human civilisation and life in general means that it is very important that we study it and learn as much about it as we can. Another good reason for this is that it can tell us a great deal about the place where it is generated: the deep interior of the Earth. At any one point on the Earth's surface, the magnetic field has both direction and intensity which both vary rather erratically in time. To study the present-day behaviour of the Earth's magnetic field, we use specialist satellites and a global network of magnetic observatories. To study the field in the distant past, we must turn to the geological record and volcanic rocks in particular. These lock-in the direction and intensity of the field at the time and place that they cool from molten lava and therefore provide a globally-distributed 'palaeomagnetic' record for almost the whole of Earth's history. The ancient direction of the Earth's magnetic field as recorded in rocks is much easier to measure than is its ancient strength (called its 'palaeointensity'). However, absolute palaeointensity records are essential for allowing us understand the geomagnetic field and its history. The problem with measuring the palaeointensity is that the rocks which are used can be affected by many complex physical factors which can bias the result. Furthermore, the precise way the measurement is carried out can also affect its reliability. A lot of recent work has gone into improving our understanding of these problems but a lack of synthesis means that palaeomagnetists still do not agree on which rocks and experimental methods produce reliable palaeointensity measurements. There is also some disagreement over which of the thousands of palaeointensity measurements which have already been published can be trusted and which should be disregarded as unreliable. These disagreements could largely be overcome if we had objective, quantitative information about the likely success of any particular palaeointensity experiment. My proposal is to provide this by developing an entirely new 'stochastic' (i.e. partially random) numerical model of palaeointensity experiments which can optimise: experimental design, analytical and procedure, and objectively determine the reliability of published data. I will rigorously constrain and test this model using new and published experimental data and ultimately, I will employ it to obtain important new information including the strength of the Earth's magnetic field more than 3 billion years ago. The benefits of this work will be considerable. It will enable future palaeointensity studies to be performed with much greater efficiency and will also allow us to get the most out of the thousands of palaeointensity determinations which are already published. Our understanding of the Earth's magnetic field, its formation in the outer core, and its protection of society and life as a whole will all be improved as a result.
Publications
Haldan M
(2009)
A comparison of detailed equatorial red bed records of secular variation during the Permo-Carboniferous Reversed Superchron
in Geophysical Journal International
Biggin A
(2014)
A new set of qualitative reliability criteria to aid inferences on palaeomagnetic dipole moment variations through geological time
in Frontiers in Earth Science
Michalk D
(2010)
Application of the multispecimen palaeointensity method to Pleistocene lava flows from the Trans-Mexican Volcanic Belt
in Physics of the Earth and Planetary Interiors
Ertepinar P
(2012)
Archaeomagnetic study of five mounds from Upper Mesopotamia between 2500 and 700 BCE: Further evidence for an extremely strong geomagnetic field ca. 3000 years ago
in Earth and Planetary Science Letters
Biggin A
(2010)
Are systematic differences between thermal and microwave Thellier-type palaeointensity estimates a consequence of multidomain bias in the thermal results?
in Physics of the Earth and Planetary Interiors
Deenen M
(2011)
Geomagnetic secular variation and the statistics of palaeomagnetic directions Statistics of palaeomagnetic directions
in Geophysical Journal International
De Groot L
(2015)
High paleointensities for the Canary Islands constrain the Levant geomagnetic high
in Earth and Planetary Science Letters
Paterson G
(2014)
On improving the selection of Thellier-type paleointensity data
in Geochemistry, Geophysics, Geosystems
Biggin A
(2011)
Palaeomagnetism of Archaean rocks of the Onverwacht Group, Barberton Greenstone Belt (southern Africa): Evidence for a stable and potentially reversing geomagnetic field at ca. 3.5Ga
in Earth and Planetary Science Letters
Biggin A
(2011)
Paleointensity Database Updated and Upgraded
in Eos, Transactions American Geophysical Union
Biggin A
(2012)
Possible links between long-term geomagnetic variations and whole-mantle convection processes
in Nature Geoscience
De Groot LV
(2013)
Rapid regional perturbations to the recent global geomagnetic decay revealed by a new Hawaiian record.
in Nature communications
Poletti W
(2013)
The cooling-rate effect on microwave archeointensity estimates
in Geophysical Research Letters
Biggin A
(2013)
The effect of cooling rate on the intensity of thermoremanent magnetization (TRM) acquired by assemblages of pseudo-single domain, multidomain and interacting single-domain grains
in Geophysical Journal International
Monster M
(2015)
The performance of various palaeointensity techniques as a function of rock magnetic behaviour - A case study for La Palma
in Physics of the Earth and Planetary Interiors
Paterson G
(2015)
Thellier-type paleointensity data from multidomain specimens
in Physics of the Earth and Planetary Interiors
Paterson G
(2012)
Towards the robust selection of Thellier-type paleointensity data: The influence of experimental noise
in Geochemistry, Geophysics, Geosystems
Description | The aim of this project was to improve our ability to make measurements of the Earth's magnetic field (its strength in particular) in the distant past and to use these to better understand how it is generated in the planet's core and how it may behave in the future. The key findings were: - Thanks to multiple experimental and numerical analyses, we now understand much better how to efficiently obtain and recognise reliable measurements of the ancient field intensity. Our new tools, protocols, and data have been made available for the rest of the research community to use in their own analyses. - We have measured the direction of the magnetic field recorded in 3.5 billion year old rocks from South Africa and shown that the field was broadly similar to today's early in the Earth's history. This is puzzling because the conditions in the core of the planet were quite different back then. - We have measured the strength of the magnetic field over the last 5,000 years in Turkey and in Hawaii. We have shown that the field can increase its strength significantly in a matter of decades and that, although it is presently weakening, it is fluctuating in time and space as it does. |
Exploitation Route | Our new techniques will be applied to document, and hence better understand, geomagnetic field behaviour on a range of timescales. |
Sectors | Environment |
Description | Our 2011 paper on the magnetism of 3.5 billion year old rocks from South Africa was chosen as an "Editor's highlight" for the major publication Science |
First Year Of Impact | 2011 |
Sector | Education |
Impact Types | Societal |
Description | Leverhulme Research Leadership Award |
Amount | £999,592 (GBP) |
Funding ID | RL-2016-080 |
Organisation | The Leverhulme Trust |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 06/2017 |
End | 07/2022 |
Description | NERC Standard Grant |
Amount | £254,678 (GBP) |
Funding ID | NE/H021043/1 |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 12/2010 |
End | 06/2014 |
Description | NERC Standard Grant |
Amount | £436,183 (GBP) |
Funding ID | NE/P00170X/1 |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 12/2016 |
End | 08/2020 |
Description | NERC Strategic Capital Grant |
Amount | £384,814 (GBP) |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 12/2013 |
End | 12/2015 |
Description | Royal Society International Exchanges |
Amount | £3,000 (GBP) |
Funding ID | IE131187 |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 03/2014 |
End | 06/2014 |
Description | Royal Society Research Grant |
Amount | £13,000 (GBP) |
Funding ID | RG130771 |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 03/2014 |
End | 04/2015 |
Title | PINT database |
Description | A global open-access database of absolute palaeointensity has been continually updated, analysed, and improved. |
Type Of Material | Database/Collection of data |
Provided To Others? | Yes |
Impact | Three papers have been published describing updates to the database: Biggin et al. (2009a,b) Biggin & Paterson (2014) These have so far been cited more than 50 times. Additionally, it formed the basis for a working group at a recent international workshop in Oslo. |
URL | http://earth.liv.ac.uk/pint/ |
Description | Greig Paterson |
Organisation | Chinese Academy of Sciences |
Country | China |
Sector | Public |
PI Contribution | Provided specialist palaeointensity expertise and measurement data. |
Collaborator Contribution | Provided computer modelling results and written up research |
Impact | Paterson et al. (2012) Paterson et al. (2014) Biggin et al. (2014) |
Start Year | 2011 |
Description | Utrecht |
Organisation | Utrecht University |
Country | Netherlands |
Sector | Academic/University |
PI Contribution | Provided training in the use of, measurements, and interpretation of data from the microwave palaeointensity system. Sent a PhD student to Utrecht to make measurements using their robot magnetometer. |
Collaborator Contribution | Sent students over to use the Liverpool microwave palaeointensity system. |
Impact | Biggin et al. (2011) Deenen et al. (2011) Ertepinar et al. (2012) de Groot et al. (2013) Roberts-Artal (submitted) Monster et al. (submitted) Another paper near submission |
Start Year | 2009 |
Description | Media surrounding 2015 inner core paper |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | A press release was made following the publication of Biggin et al. (2015) in Nature. This was picked up well by media organisations internationally (e.g. BBC, Mail online, El Pais, ABC, etc) and involved a radio interview broadcast on the BBC World Service. |
Year(s) Of Engagement Activity | 2015 |
URL | http://www.bbc.co.uk/news/science-environment-34475464 |