4.6 Article

Can one use Earth's magnetic axial dipole field intensity to predict reversals?

期刊

GEOPHYSICAL JOURNAL INTERNATIONAL
卷 225, 期 1, 页码 277-297

出版社

OXFORD UNIV PRESS
DOI: 10.1093/gji/ggaa542

关键词

Dynamo: theories and simulations; Magnetic field variations through time; Palaeointensity; Reversals: process; timescale; magnetostratigraphy; Time-series analysis

资金

  1. NASA Headquarters [80NSSC18K1351]
  2. French Agence Nationale de la Recherche [ANR-19-CE31-0019]
  3. GENCI [GCH0315, A0060407382]
  4. Agence Nationale de la Recherche (ANR) [ANR-19-CE31-0019] Funding Source: Agence Nationale de la Recherche (ANR)

向作者/读者索取更多资源

This study focuses on predicting reversals of Earth's axial magnetic dipole field based on the intensity of the dipole. The prediction strategy varies in skill across different numerical models, serving as an additional criterion to identify Earth-like models. Applying threshold-based predictions to paleomagnetic reconstructions suggests moderate skill in predicting Earth's dynamo over the last two million years.
We study predictions of reversals of Earth's axial magnetic dipole field that are based solely on the dipole's intensity. The prediction strategy is, roughly, that once the dipole intensity drops below a threshold, then the field will continue to decrease and a reversal (or a major excursion) will occur. We first present a rigorous definition of an intensity threshold-based prediction strategy and then describe a mathematical and numerical framework to investigate its validity and robustness in view of the data being limited. We apply threshold-based predictions to a hierarchy of numerical models, ranging from simple scalar models to 3-D geodynamos. We find that the skill of threshold-based predictions varies across the model hierarchy. The differences in skill can be explained by differences in how reversals occur: if the field decreases towards a reversal slowly (in a sense made precise in this paper), the skill is high, and if the field decreases quickly, the skill is low. Such a property could be used as an additional criterion to identify which models qualify as Earth-like. Applying threshold-based predictions to Virtual Axial Dipole Moment palaeomagnetic reconstructions (PADM2M and Sint-2000) covering the last two million years, reveals a moderate skill of threshold-based predictions for Earth's dynamo. Besides all of their limitations, threshold-based predictions suggests that no reversal is to be expected within the next 10 kyr. Most importantly, however, we show that considering an intensity threshold for identifying upcoming reversals is intrinsically limited by the dynamic behaviour of Earth's magnetic field.

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