Recent north magnetic pole acceleration towards Siberia caused by flux lobe elongation

Abstract

The wandering of Earth’s north magnetic pole, the location where the magnetic field points vertically downwards, has long been a topic of scientific fascination. Since the first in situ measurements in 1831 of its location in the Canadian arctic, the pole has drifted inexorably towards Siberia, accelerating between 1990 and 2005 from its historic speed of 0–15 km yr−1 to its present speed of 50–60 km yr−1. In late October 2017 the north magnetic pole crossed the international date line, passing within 390 km of the geographic pole, and is now moving southwards. Here we show that over the last two decades the position of the north magnetic pole has been largely determined by two large-scale lobes of negative magnetic flux on the core–mantle boundary under Canada and Siberia. Localized modelling shows that elongation of the Canadian lobe, probably caused by an alteration in the pattern of core flow between 1970 and 1999, substantially weakened its signature on Earth’s surface, causing the pole to accelerate towards Siberia. A range of simple models that capture this process indicate that over the next decade the north magnetic pole will continue on its current trajectory, travelling a further 390–660 km towards Siberia.

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Fig. 1: Historical movement and predicted future path of the north magnetic pole in stereographic projection.
Fig. 2: A comparison of the structure of the geomagnetic field and the north magnetic pole position in orthographic projection between 2019 and 1999.
Fig. 3: Experiment demonstrating the effect of elongation of the Canadian CMB flux lobe on the large-scale surface field and pole position.
Fig. 4: Local core surface dynamics around the Canadian flux lobe in stereographic projection.

Data availability

The CHAOS-6-x8 and COV-OBS.x1 geomagnetic field models on which this study is based can be found at http://www.spacecenter.dk/files/magnetic-models/

The flow models of Barrois et al. employed here can be found at https://geodyn.univ-grenoble-alpes.fr/

Code availability

All codes are freely available by request from the corresponding author.

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Acknowledgements

P.W.L. acknowledges funding from the Natural Environment Research Council (NERC) grant NE/P016758/1. C.C.F. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme, grant agreement 772561.

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Authors

Contributions

P.W.L. and C.C.F. devised the study; calculations were performed by P.W.L. and M.B. C.C.F. derived the CHAOS-6-x8 field model. P.W.L. and C.C.F. analysed the geomagnetic field and core-flow models, interpreted the results and wrote the paper. All authors commented on the manuscript.

Corresponding author

Correspondence to Philip W. Livermore.

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Competing interests

The authors declare no competing interests.

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Peer review information Primary Handling Editor: Tamara Goldin.

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Extended data

Extended Data Fig. 1 North magnetic pole sensitivity on geomagnetic field changes beneath the New Siberian Islands.

In this test, as described in the main text, between 1999–2019 the geomagnetic field on the CMB is allowed to evolve (according to CHAOS-6-x8) only within the shown wedge (centred on the New Siberian Islands). The resulting path of the north magnetic pole shows the insensitivity of the pole to secular variation restricted to this region, and is shown 1999–2019 by the red line. We have omitted to plot the red star (which is included in the other figures) since it would hide the path.

Extended Data Fig. 2 North magnetic pole sensitivity on geomagnetic field changes beneath a high latitude reversed flux patch.

In this test, as described in the main text, between 1999–2019 the geomagnetic field on the CMB is allowed to evolve (according to CHAOS-6-x8) only within the shown wedge (centred on the high latitude reversed flux patch which the north magnetic pole is currently traversing). The resulting very short path of the north magnetic pole shows the insensitivity of the pole to secular variation restricted to this region, and is shown 1999–2019 by the red line (which appears here as a single dot). We have omitted to plot the red star (which is included in the other figures) since it would hide the path.

Supplementary information

41561_2020_570_MOESM1_ESM.mp4

Evolution of the north magnetic pole 1999–2019. The video shows the location of the north magnetic pole projected on the CMB, according to CHAOS-6-x8 (red star), with the red solid tail showing the path since 1999; contours show radial magnetic field on the CMB. The tangent cylinder is shown by the orange circle.

41561_2020_570_MOESM2_ESM.mp4

Evolution of the north magnetic pole 1840–2015. The video shows the location of the north magnetic pole projected on the CMB, according to COV-OBS.x1 (red star), with the red solid tail showing the path since 1840; contours show radial magnetic field on the CMB. The tangent cylinder is shown by the orange circle.

Supplementary Video 1

Evolution of the north magnetic pole 1999–2019. The video shows the location of the north magnetic pole projected on the CMB, according to CHAOS-6-x8 (red star), with the red solid tail showing the path since 1999; contours show radial magnetic field on the CMB. The tangent cylinder is shown by the orange circle.

Supplementary Video 2

Evolution of the north magnetic pole 1840–2015. The video shows the location of the north magnetic pole projected on the CMB, according to COV-OBS.x1 (red star), with the red solid tail showing the path since 1840; contours show radial magnetic field on the CMB. The tangent cylinder is shown by the orange circle.

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Livermore, P.W., Finlay, C.C. & Bayliff, M. Recent north magnetic pole acceleration towards Siberia caused by flux lobe elongation. Nat. Geosci. 13, 387–391 (2020). https://doi.org/10.1038/s41561-020-0570-9

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