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| Titel |
Predicting geomagnetic reversals via data assimilation: a feasibility study |
| VerfasserIn |
Matthias Morzfeld, Alexandre Fournier, Gauthier Hulot |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093797
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| Publikation (Nr.) |
 EGU/EGU2014-8869.pdf |
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| Zusammenfassung |
| The system of three ordinary differential equations (ODE) presented by Gissinger in [1] was
shown to exhibit chaotic reversals whose statistics compared well with those from the
paleomagnetic record. We explore the geophysical relevance of this low-dimensional model
via data assimilation, i.e.we update the solution of the ODE with information from data of
the dipole variable. The data set we use is “SINT” (Valet et al.[2]), and it provides the signed
virtual axial dipole moment over the past 2 millions years. We can obtain an accurate
reconstruction of these dipole data using implicit sampling (a fully nonlinear Monte
Carlo sampling strategy) and assimilating 5 kyr of data per sweep. We confirm
our calibration of the model using the PADM2M dipole data set of Ziegler et al.
[3].
The Monte Carlo sampling strategy provides us with quantitative information about the
uncertainty of our estimates, and –in principal– we can use this information for making
(robust) predictions under uncertainty. We perform synthetic data experiments to explore the
predictive capability of the ODE model updated by data assimilation. For each experiment,
we produce 2 Myr of synthetic data (with error levels similar to the ones found in the SINT
data), calibrate the model to this record, and then check if this calibrated model can reliably
predict a reversal within the next 5 kyr. By performing a large number of such experiments,
we can estimate the statistics that describe how reliably our calibrated model can predict a
reversal of the geomagnetic field. It is found that the 1 kyr-ahead predictions of
reversals produced by the model appear to be accurate and reliable. These encouraging
results prompted us to also test predictions of the five reversals of the SINT (and
PADM2M) data set, using a similarly calibrated model. Results will be presented and
discussed.
References
Gissinger, C., 2012, A new deterministic model for chaotic reversals, European
Physical Journal B, 85:137
Valet, J.P., Maynadier,L and Guyodo, Y., 2005, Geomagnetic field strength and
reversal rate over the past 2 Million years, Nature, 435, 802-805.
Ziegler, L.B., Constable, C.G., Johnson, C.L. and Tauxe, L., 2011, PADM2M: a
penalized maximum likelihood moidel of the 0-2 Ma paleomagnetic axial dipole
moment, Geophysical Journal International, 184, 1069-1089. |
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