EGU21-7139
https://doi.org/10.5194/egusphere-egu21-7139
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Inversion of the satellite observations of the tidally induced magnetic field in terms of 3-D upper-mantle electrical conductivity: Method and synthetic tests

Libor Šachl1, Jakub Velímský1, and Javier Fullea2,3
Libor Šachl et al.
  • 1Department of Geophysics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
  • 2Department of Physics of the Earth and Astrophysics, Faculty of Physics, University of Madrid, Madrid, Spain
  • 3Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland

We have developed and tested a new frequency-domain, spherical harmonic-finite element approach to the inverse problem of global electromagnetic (EM) induction. It is based on the quasi-Newton minimization of data misfit and regularization, and uses the adjoint approach for fast calculation of misfit gradients in the model space. Thus, it allows for an effective inversion of satellite-observed magnetic field induced by tidally driven flows in the Earth's oceans in terms of 3-D structure of the electrical conductivity in the upper mantle. Before proceeding to the inversion of Swarm-derived models of tidal magnetic signatures, we have performed a series of parametric studies, using a 3-D conductivity model WINTERC-e as a testbed.

The WINTERC-e model has been derived using state-of-the-art laboratory conductivity measurements of mantle minerals, and thermal and compositional model of the lithosphere and upper mantle WINTERC-grav. The latter model is based on the inversion of global surface waveforms, satellite gravity and gradiometry measurements, surface elevation, and heat flow data in a thermodynamically self-consistent framework. Therefore, the WINTERC-e model, independent of any EM data, represents an ideal target for synthetic tests of the 3-D EM inversion.

We tested the impact of the satellite altitude, the truncation degree of the spherical-harmonic expansion of the tidal signals, the random noise in data, and of the sub-continental conductivity on the ability to recover the sub-oceanic upper-mantle conductivity structure. We demonstrate that with suitable regularization we can successfully reconstruct the 3D upper-mantle conductivity below world oceans.

How to cite: Šachl, L., Velímský, J., and Fullea, J.: Inversion of the satellite observations of the tidally induced magnetic field in terms of 3-D upper-mantle electrical conductivity: Method and synthetic tests, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7139, https://doi.org/10.5194/egusphere-egu21-7139, 2021.

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