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Volume 36, issue 4 | Copyright

Special issue: Dynamics and interaction of processes in the Earth and its...

Ann. Geophys., 36, 1009-1014, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 17 Jul 2018

Regular paper | 17 Jul 2018

Estimating ocean tide model uncertainties for electromagnetic inversion studies

Jan Saynisch1, Christopher Irrgang1, and Maik Thomas1,2 Jan Saynisch et al.
  • 1Earth System Modelling, Helmholtz Centre Potsdam, GFZ German Research Centre Potsdam, Potsdam, Germany
  • 2Institute of Meteorology, Freie Universität Berlin, Berlin, Germany

Abstract. Over a decade ago the semidiurnal lunar M2 ocean tide was identified in CHAMP satellite magnetometer data. Since then and especially since the launch of the satellite mission Swarm, electromagnetic tidal observations from satellites are increasingly used to infer electric properties of the upper mantle. In most of these inversions, ocean tidal models are used to generate oceanic tidal electromagnetic signals via electromagnetic induction. The modeled signals are subsequently compared to the satellite observations. During the inversion, since the tidal models are considered error free, discrepancies between forward models and observations are projected only onto the induction part of the modeling, e.g., Earth's conductivity distribution. Our study analyzes uncertainties in oceanic tidal models from an electromagnetic point of view. Velocities from hydrodynamic and assimilative tidal models are converted into tidal electromagnetic signals and compared. Respective uncertainties are estimated. The studies main goal is to provide errors for electromagnetic inversion studies. At satellite height, the differences between the hydrodynamic tidal models are found to reach up to 2nT, i.e., over 100% of the local M2 signal. Assimilative tidal models show smaller differences of up to 0.1nT, which in some locations still corresponds to over 30% of the M2 signal.

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Short summary
By induction, ocean tides generate electromagnetic signals. Since the launch of magnetometer satellite missions, these signals are increasingly used to infer electromagnetic properties of the Earth. In many of these inversions, ocean tide models are used to estimate oceanic tidal electromagnetic signals which are generated via electromagnetic induction. This study's goal is to provide tide model errors for electromagnetic inversion studies.
By induction, ocean tides generate electromagnetic signals. Since the launch of magnetometer...