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Melting of the Earth’s inner core


The Earth’s magnetic field is generated by a dynamo in the liquid iron core, which convects in response to cooling of the overlying rocky mantle. The core freezes from the innermost surface outward, growing the solid inner core and releasing light elements that drive compositional convection1,2,3. Mantle convection extracts heat from the core at a rate that has enormous lateral variations4. Here we use geodynamo simulations to show that these variations are transferred to the inner-core boundary and can be large enough to cause heat to flow into the inner core. If this were to occur in the Earth, it would cause localized melting. Melting releases heavy liquid that could form the variable-composition layer suggested by an anomaly in seismic velocity in the 150 kilometres immediately above the inner-core boundary5,6,7. This provides a very simple explanation of the existence of this layer, which otherwise requires additional assumptions such as locking of the inner core to the mantle, translation from its geopotential centre7,8 or convection with temperature equal to the solidus but with composition varying from the outer to the inner core9. The predominantly narrow downwellings associated with freezing and broad upwellings associated with melting mean that the area of melting could be quite large despite the average dominance of freezing necessary to keep the dynamo going. Localized melting and freezing also provides a strong mechanism for creating seismic anomalies in the inner core itself, much stronger than the effects of variations in heat flow so far considered10.

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Figure 1: Effect of mantle inhomogeneity on heat flux distribution at the inner core surface.
Figure 2: Calculated heat flux on the lower boundary of a geodynamo model where q* = 0.15 for the upper boundary heat flux.
Figure 3: Temperature (colour contours) and fluid flow (arrows) on the equatorial section for the statistically locked tomographic model (q* = 0.45).

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  1. Braginsky, S. I. Structure of the F layer and reasons for convection in the Earth’s core. Dokl. Akad. Nauk. SSSR (Engl. Trans.) 149, 1311–1314 (1963)

    Google Scholar 

  2. Labrosse, S., Poirier, J.-P. & Le Mouël, J.-L. On cooling of the Earth’s core. Phys. Earth Planet. Inter. 99, 1–17 (1997)

    Article  ADS  Google Scholar 

  3. Nimmo, F., Price, G. D., Brodholt, J. & Gubbins, D. The influence of potassium on core and geodynamo evolution. Geophys. J. Int. 156, 363–376 (2004)

    Article  ADS  CAS  Google Scholar 

  4. Nakagawa, T. & Tackley, P. J. Lateral variations in CMB heat flux and deep mantle seismic velocity caused by a thermal-chemical-phase boundary layer in 3D spherical convection. Earth Planet. Sci. Lett. 271, 348–358 (2008)

    Article  ADS  CAS  Google Scholar 

  5. Souriau, A. & Poupinet, G. The velocity profile at the base of the liquid core from PKP(BC+Cdiff) data: an argument in favor of radial inhomogeneity. Geophys. Res. Lett. 18, 2023–2026 (1991)

    Article  ADS  Google Scholar 

  6. Song, X. D. & Helmberger, D. V. Velocity structure near the inner core boundary from waveform modeling. J. Geophys. Res. 97, 6573–6586 (1992)

    Article  ADS  Google Scholar 

  7. Monnereau, M., Calvet, M., Margerin, L. & Souriau, A. Lopsided growth of Earth’s inner core. Science 328, 1014–1017 (2010)

    Article  ADS  CAS  PubMed  Google Scholar 

  8. Alboussière, T., Deguen, R. & Melzani, M. Melting-induced stratification above the Earth’s inner core due to convective translation. Nature 466, 744–747 (2010)

    Article  ADS  CAS  PubMed  Google Scholar 

  9. Gubbins, D., Masters, G. & Nimmo, F. A thermochemical boundary layer at the base of Earth’s outer core and independent estimate of core heat flux. Geophys. J. Int. 174, 1007–1018 (2008)

    Article  ADS  Google Scholar 

  10. Aubert, J., Amit, H. & Hulot, G. Detecting thermal boundary control in surface flows from numerical dynamos. Phys. Earth Planet. Inter. 160, 143–156 (2007)

    Article  ADS  Google Scholar 

  11. Masters, T. G., Johnson, S., Laske, G. & Bolton, H. F. A shear-velocity model of the mantle. Phil. Trans. R. Soc. Lond. A 354, 1385–1411 (1996)

    Article  ADS  Google Scholar 

  12. Zhang, K. & Gubbins, D. Convection in a rotating spherical fluid shell with an inhomogeneous temperature boundary condition at finite Prandtl number. Phys. Fluids 8, 1141–1148 (1996)

    Article  ADS  CAS  MATH  Google Scholar 

  13. Zhang, K. & Gubbins, D. Scale disparities and magnetohydrodynamics in the Earth’s core. Phil. Trans. R. Soc. Lond. A 358, 899–920 (2000)

    Article  ADS  MathSciNet  MATH  Google Scholar 

  14. Gibbons, S. & Gubbins, D. Convection in the Earth's core driven by lateral variations in the core-mantle boundary heat flux. Geophys. J. Int. 142, 631–642 (2000)

    Article  ADS  Google Scholar 

  15. Sreenivasan, B. On dynamo action produced by boundary thermal coupling. Phys. Earth Planet. Inter. 177, 130–138 (2009)

    Article  ADS  Google Scholar 

  16. Bloxham, J. The effect of thermal core-mantle interactions on the paleomagnetic secular variation. Phil. Trans. R. Soc. Lond. A 358, 1171–1179 (2000)

    Article  ADS  Google Scholar 

  17. Christensen, U., Olson, P. & Glatzmaier, G. A. A dynamo model interpretation of geomagnetic field structures. Geophys. Res. Lett. 25, 1565–1568 (1998)

    Article  ADS  Google Scholar 

  18. Olson, P. & Christensen, U. R. The time-averaged magnetic field in numerical dynamos with non-uniform boundary heat flow. Geophys. J. Int. 151, 809–823 (2002)

    Article  ADS  Google Scholar 

  19. Christensen, U. R. & Olson, P. Secular variation in numerical geodynamo models with lateral variations of boundary heat flow. Phys. Earth Planet. Inter. 138, 39–54 (2003)

    Article  ADS  Google Scholar 

  20. Glatzmaier, G. A., Coe, R. S., Hongre, L. & Roberts, P. H. The role of the Earth’s mantle in controlling the frequency of geomagnetic reversals. Nature 401, 885–890 (1999)

    Article  ADS  Google Scholar 

  21. Kutzner, C. & Christensen, U. R. Simulated geomagnetic reversals and preferred virtual geomagnetic pole paths. Geophys. J. Int. 157, 1105–1118 (2004)

    Article  ADS  Google Scholar 

  22. Gubbins, D., Willis, A. P. & Sreenivasan, B. Correlation of Earth’s magnetic field with lower mantle thermal and seismic structure. Phys. Earth Planet. Inter. 162, 256–260 (2007)

    Article  ADS  Google Scholar 

  23. Sreenivasan, B. & Gubbins, D. Dynamos with weakly convecting outer layers: implications for core–mantle boundary interaction. Geophys. Astrophys. Fluid Dyn. 102, 395–407 (2008)

    Article  ADS  MathSciNet  Google Scholar 

  24. Buffett, B. A. & Seagle, C. T. Stratification of the top of the core due to chemical interactions with the mantle. J. Geophys. Res. 115, B04407 (2010)

    Article  ADS  CAS  Google Scholar 

  25. Helffrich, G. & Kaneshima, S. Outer-core compositional stratification from observed core wave speed profiles. Nature 468, 807–810 (2010)

    Article  ADS  CAS  PubMed  Google Scholar 

  26. Dziewonski, A. M. & Anderson, D. L. Preliminary Reference Earth Model. Phys. Earth Planet. Inter. 25, 297–356 (1981)

    Article  ADS  Google Scholar 

  27. Gubbins, D., Alfè, D., Masters, T. G. & Price, D. Gross thermodynamics of 2-component core convection. Geophys. J. Int. 157, 1407–1414 (2004)

    Article  ADS  CAS  Google Scholar 

  28. Moffatt, H. K. & Loper, D. E. The magnetostrophic rise of a buoyant parcel in the Earth’s core. Geophys. J. Int. 117, 394–402 (1994)

    Article  ADS  Google Scholar 

  29. Aubert, J., Amit, H., Hulot, G. & Olson, P. Thermochemical flows couple the Earth’s inner core growth to mantle heterogeneity. Nature 454, 758–761 (2008)

    Article  ADS  CAS  PubMed  Google Scholar 

  30. Sreenivasan, B. A buoyant flow structure in a magnetic field: quasi-steady states and linear–nonlinear transitions. Phys. Lett. A 372, 5471–5478 (2008)

    Article  ADS  MathSciNet  CAS  MATH  Google Scholar 

  31. Sreenivasan, B. & Jones, C. A. The role of inertia in the evolution of spherical dynamos. Geophys. J. Int. 164, 467–476 (2006)

    Article  ADS  Google Scholar 

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B.S. set up the geodynamo model and performed the calculations that form the basis of this paper. All four authors discussed the results and contributed to the text of the manuscript.

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Correspondence to Binod Sreenivasan.

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The authors declare no competing financial interests.

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Gubbins, D., Sreenivasan, B., Mound, J. et al. Melting of the Earth’s inner core. Nature 473, 361–363 (2011).

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