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

TL;DR

This study evaluates the effectiveness of using Earth's magnetic dipole intensity thresholds to predict geomagnetic reversals, revealing moderate predictive skill and intrinsic limitations based on reversal dynamics.

Contribution

The paper introduces a rigorous framework for threshold-based reversal prediction and assesses its validity across models and paleomagnetic data, highlighting the influence of reversal dynamics.

Findings

Prediction skill varies with reversal dynamics

Slow field decreases lead to higher prediction skill

No reversals expected within the next 10,000 years

Abstract

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 3D 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 (VADM) paleomagnetic 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 suggest 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 behavior of Earth's magnetic field.