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Ocean Science An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 1
Ocean Sci., 12, 129–136, 2016
https://doi.org/10.5194/os-12-129-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ocean Sci., 12, 129–136, 2016
https://doi.org/10.5194/os-12-129-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Jan 2016

Research article | 15 Jan 2016

Impact of variable seawater conductivity on motional induction simulated with an ocean general circulation model

C. Irrgang1,2, J. Saynisch1, and M. Thomas1,2 C. Irrgang et al.
  • 1Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Section 1.3, Earth System Modelling, Potsdam, Germany
  • 2Freie Universität Berlin, Institute of Meteorology, Berlin, Germany

Abstract. Carrying high concentrations of dissolved salt, ocean water is a good electrical conductor. As seawater flows through the Earth's ambient geomagnetic field, electric fields are generated, which in turn induce secondary magnetic fields. In current models for ocean-induced magnetic fields, a realistic consideration of seawater conductivity is often neglected and the effect on the variability of the ocean-induced magnetic field unknown. To model magnetic fields that are induced by non-tidal global ocean currents, an electromagnetic induction model is implemented into the Ocean Model for Circulation and Tides (OMCT). This provides the opportunity to not only model ocean-induced magnetic signals but also to assess the impact of oceanographic phenomena on the induction process. In this paper, the sensitivity of the induction process due to spatial and temporal variations in seawater conductivity is investigated. It is shown that assuming an ocean-wide uniform conductivity is insufficient to accurately capture the temporal variability of the magnetic signal. Using instead a realistic global seawater conductivity distribution increases the temporal variability of the magnetic field up to 45 %. Especially vertical gradients in seawater conductivity prove to be a key factor for the variability of the ocean-induced magnetic field. However, temporal variations of seawater conductivity only marginally affect the magnetic signal.

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In this study, the influence of a spatio-temporally variable seawater conductivity on ocean-circulation-induced magnetic signals is investigated. To simulate the ocean-circulation-induced magnetic field, a combination of an ocean general circulation model (OMCT) and an electromagnetic induction model is used. It is found that a spatially varying seawater conductivity has a significant impact on the temporal variability of the induced magnetic field.
In this study, the influence of a spatio-temporally variable seawater conductivity on...
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