Maffei, S, Livermore, PW orcid.org/0000-0001-7591-6716, Mound, JE orcid.org/0000-0002-1243-6915 et al. (2 more authors) (2021) Fast Directional Changes during Geomagnetic Transitions: Global Reversals or Local Fluctuations? Geosciences, 11 (8). 318. ISSN 2076-3263
Abstract
Paleomagnetic investigations from sediments in Central and Southern Italy found directional changes of the order of 10∘ per year during the last geomagnetic field reversal (which took place about 780,000 years ago). These values are orders of magnitudes larger than what is expected from the estimated millennial timescales for geomagnetic field reversals. It is yet unclear whether these extreme changes define the timescale of global dipolar change or whether they indicate a rapid, but spatially localised feature that is not indicative of global variations. Here, we address this issue by calculating the minimum amount of kinetic energy that flows at the top of the core required to instantaneously reproduce these two scenarios. We found that optimised flow structures compatible with the global-scale interpretation of directional change require about one order of magnitude more energy than those that reproduce local change. In particular, we found that the most recently reported directional variations from the Sulmona Basin, in Central Italy, can be reproduced by a core-surface flow with rms values comparable to, or significantly lower than, present-day estimates of about 8 to 22 km/y. Conversely, interpreting the observations as global changes requires rms flow values in excess of 77 km/y, with pointwise maximal velocities of 127 km/y, which we deem improbable. We therefore concluded that the extreme variations reported for the Sulmona Basin were likely caused by a local, transient feature during a longer transition.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
Keywords: | paleomagnetism; rapid variations; Earth’s outer core |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/V009052/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Sep 2021 10:59 |
Last Modified: | 10 Sep 2021 10:59 |
Status: | Published online |
Publisher: | MDPI |
Identification Number: | 10.3390/geosciences11080318 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:178000 |