Heterogeneity in core-mantle heat flow influenced the ancient geodynamo

Heterogeneity in core-mantle heat flow influenced the ancient geodynamo | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Heterogeneity in core-mantle heat flow influenced the ancient geodynamo Andrew Biggin, Christopher Davies, Jonathan Mound, Simon Lloyd, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6314721/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Feb, 2026 Read the published version in Nature Geoscience → Version 1 posted You are reading this latest preprint version Abstract Studies of the behaviour of the geodynamo through time, preserved in palaeomagnetic records, have a unique potential to inform us about the time-varying thermal structure of Earth’s core-mantle boundary region. In practise, however, such insights have proved difficult to obtain because of the limited spatiotemporal resolution of palaeomagnetic records and uncertainties in how to interpret them. Here we show that certain key characteristics of the palaeomagnetic field observed over the last 23 Myr can only be reproduced by numerical simulations of the geodynamo that have heterogeneous heat flux conditions imposed on their outer boundaries. We further demonstrate that a signal of azimuthal asymmetry in field behaviour, characteristic of such heterogeneity, is evident in the variance of records of palaeosecular variation recovered from low latitudes, that are up to 265 Myr old. Finally, we show that imposing strong heterogeneity in the heat flow boundary conditions significantly increases the parameter range over which simulations can reproduce aspects of palaeosecular variation that have been observed to be stable through much of geological time. In conjunction, these findings provide compelling new evidence that significant thermal heterogeneity at the core-mantle boundary has influenced the geodynamo for at least the last few hundred million years. The identified palaeomagnetic signatures of thermal heterogeneity at the core-mantle boundary provide a new means to constrain the properties and time-evolution of this region of Earth’s interior. Furthermore, our insights into how thermal heterogeneity at the base of the mantle can break the axial symmetry of the time-averaged magnetic field may provide an important step towards resolving longstanding palaeogeographic controversies. Earth and environmental sciences/Solid Earth sciences/Palaeomagnetism Earth and environmental sciences/Solid Earth sciences/Core processes Earth and environmental sciences/Solid Earth sciences/Geomagnetism Earth and environmental sciences/Solid Earth sciences/Geodynamics Full Text Additional Declarations There is NO Competing Interest. Supplementary Files TableS1.pdf Table S1 TableS2.pdf Table S2 SupplementaryDataset1.xlsx Dataset 1 Cite Share Download PDF Status: Published Journal Publication published 03 Feb, 2026 Read the published version in Nature Geoscience → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6314721","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":450303681,"identity":"c6f4b43f-8c00-4673-a29e-c76fd6f637e1","order_by":0,"name":"Andrew 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