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A polar vortex in the Earth's core

Nature volume 402, pages 170–173 (1999)Cite this article

Abstract

Numerical dynamo models have been successful in explaining the origin of the Earth's magnetic field and its secular variation by convection in the electrically conducting fluid outer core1,2,3,4,5,6,7. An important component of the convection in the numerical dynamos are polar vortices beneath the core–mantle boundary in each hemisphere. These polar vortices in the outer core have been proposed as sources for both the anomalous rotation of the inner core and the toroidal part of the geomagnetic field2,8. Here we use the observed structure of the Earth's magnetic field and its variation since 1870 to infer the existence of an anticyclonic polar vortex with a polar upwelling in the northern hemisphere of the core, consistent with the polar vortices found in numerical dynamos.

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Figure 1: Secular variation of the geomagnetic field observed over the north-polar region of the core–mantle boundary and structure of the inferred axisymmetric polar vortex in the outer core.
Figure 2: Profiles of the axisymmetric flow versus co-latitude in the inferred north-polar vortex 1870–1990.
Figure 3: Persistence of the north polar vortex since 1870, determined using different time windows of geomagnetic secular variation.

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References

  1. Glatzmaier,G. A. & Roberts,P. H. A three-dimensional self-consistent computer simulation of a geomagnetic reversal. Nature 377, 203–208 (1995).

    Article  ADS  CAS  Google Scholar 

  2. Glatzmaier,G. A. & Roberts,P. H. Rotation and magnetism of Earth's inner core. Science 274, 1887–1891 (1996).

    Article  ADS  CAS  Google Scholar 

  3. Kuang,W. & Bloxham,J. An Earth-like numerical dynamo model. Nature 389, 371–374 (1997).

    Article  ADS  CAS  Google Scholar 

  4. Busse,F. H., Grote,E. & Tilgner,A. On convection driven dynamos in rotating spherical shells. Stud. Geophys. Geodaet. 42, 1–6 (1998).

    Article  Google Scholar 

  5. Olson,P., Christensen,U. & Glatzmaier,G. A. Numerical modeling of the geodynamo: Mechanisms of field generation and equilibration. J. Geophys. Res. 104, 10383–10404 (1999).

    Article  ADS  Google Scholar 

  6. Christensen,U., Olson,P. & Glatzmaier,G. A. Numerical modeling of the geodynamo; a systematic parameter study. Geophys. J. Int. 138, 393–409 (1999).

    Article  ADS  Google Scholar 

  7. Glatzmaier,G. A., Coe,R. S., Longre,L & Roberts,P. H. The role of the Earth's mantle in controlling the frequency of geomagnetic reversals. Nature (in the press).

  8. Aurnou,J. M., Brito,D. & Olson,P. L. Mechanics of inner core super-rotation. Geophys. Res. Lett. 23, 3401–3404 (1996).

    Article  ADS  Google Scholar 

  9. Voorhies,C. V. Steady flows at the top of Earth's core derived from geomagnetic field models. J. Geophys. Res. 91, 12444–12466 (1986).

    Article  ADS  Google Scholar 

  10. Voorhies,C. V. Time-varying flows at the top of Earth's core derived from definitive geomagnetic reference models. J. Geophys. Res. 100, 10029–10039 (1995).

    Article  ADS  Google Scholar 

  11. Pais,A. & Hulot,G. Core surface zonal flows, length of day decade variations and inner core superrotation. Phys. Earth Planet. Inter. (submitted).

  12. Jault,D., Gire,C. & LeMouel,J.-L. Westward drift, core motions and exchanges of angular momentum between core and mantle. Nature 333, 353–356 (1988).

    Article  ADS  Google Scholar 

  13. Bloxham,J. The steady part of the secular variation of the Earth's magnetic field. J. Geophys. Res. 97, 19565–19579 (1992).

    Article  ADS  Google Scholar 

  14. Jackson,A. Time-dependency of tangentially geostrophic core surface motions. Phys. Earth Planet. Inter. 103, 293–311 (1997).

    Article  ADS  Google Scholar 

  15. Bloxham,J. & Jackson,A. Time-dependent mapping of the geomagnetic field at the core-mantle boundary. J. Geophys. Res. 97, 19357–19564 (1992).

    ADS  Google Scholar 

  16. Backus,G. E. Kinematics of the secular variation in a perfectly conducting core. Phil. Trans. R. Soc. Lond. A 263, 239–266 (1968).

    Article  ADS  Google Scholar 

  17. Gubbins,D. & Bloxham,J. Morphology of the geomagnetic field and implications for the geodynamo. Nature 325, 509–511 (1987).

    Article  ADS  Google Scholar 

  18. Hopfinger,E. J. & Van Heijst,G. J. F. Vortices in rotating fluids. Annu. Rev. Fluid Mech. 25, 241–289 (1993).

    Article  ADS  MathSciNet  Google Scholar 

  19. Schloeberl,M. R. & Hartmann,D. L. The dynamics of the stratospheric polar vortex and its relation to springtime ozone depletions. Science 251, 46–52 (1991).

    Article  ADS  Google Scholar 

  20. Jones,H. & Marshall,J. Convection with rotation in a neutral ocean: a study of open-ocean deep convection. J. Phys. Oceanogr. 23, 1009–1039 (1993).

    Article  ADS  Google Scholar 

  21. Rau,S., Christensen,U., Jackson,A. & Wicht,J. Core flow inversion tested with numerical dynamo models. Geophys. J. Int. (submitted).

  22. Yokoyama,Y. & Yukutake,T. Sixty year variation in a time series of the geomagnetic Gauss coefficients. J. Geomagn. Geoelectr. 43, 563–584 (1997).

    Article  ADS  Google Scholar 

  23. Stacey,F. D. Physics of the Earth (Brookfield, Brisbane, Australia, 1992).

    Google Scholar 

  24. Song,X. & Richards,P. G. Seismological evidence for the differential rotation of the Earth's inner core. Nature 382, 221–224 (1996).

    Article  ADS  CAS  Google Scholar 

  25. Creager,K. C. Inner core rotation rate from small-scale heterogeneity and time-varying travel times. Science 287, 1284–1288 (1997).

    Article  ADS  Google Scholar 

  26. Laske,G. & Masters,G. Limits on differential rotation of the inner core from an analysis of the Earth's free oscillations. Nature 402, 66–69 (1999).

    Article  ADS  CAS  Google Scholar 

  27. Voorhies,C. V. Inner core rotation from geomagnetic westward drift and a stationary spherical vortex in Earth's core. Phys. Earth Planet. Inter. 112, 111–124 (1999).

    Article  ADS  Google Scholar 

  28. Wu,C.-C. & Emanuel,K. E. Interaction of a baroclinic vortex with background shear: application to hurricane movement. J. Atmos. Sci. 50, 62–76 (1993).

    Article  ADS  Google Scholar 

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Acknowledgements

We thank J. Bloxham, Y. Hamano, and Y. Yokoyamo for providing the geomagnetic field models and D. Waugh for pointing out similarities with other geophysical vortices. A. Pais, G. Hulot, G. Laske and G. Masters kindly shared their results in advance of publication.

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  1. Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, 21218, Maryland, USA

    Peter Olson & Jonathan Aurnou

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  1. Peter Olson
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  2. Jonathan Aurnou
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Correspondence to Peter Olson.

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Olson, P., Aurnou, J. A polar vortex in the Earth's core. Nature 402, 170–173 (1999). https://doi.org/10.1038/46017

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