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Exploring effects in tippers at island geomagnetic observatories due to realistic depth- and time-varying oceanic electrical conductivity.

Urheber*innen

Rigaud,  Rafael
External Organizations;

Kruglyakov,  Mikhail
External Organizations;

Kuvshinov,  Alexey
External Organizations;

Pinheiro,  Katia J.
External Organizations;

/persons/resource/petereit

Petereit,  J.
1.3 Earth System Modelling, 1.0 Geodesy, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

/persons/resource/jmat

Matzka,  J.
2.3 Geomagnetism, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Marshalko,  Elena
External Organizations;

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5004860.pdf
(Verlagsversion), 9MB

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Zitation

Rigaud, R., Kruglyakov, M., Kuvshinov, A., Pinheiro, K. J., Petereit, J., Matzka, J., Marshalko, E. (2021): Exploring effects in tippers at island geomagnetic observatories due to realistic depth- and time-varying oceanic electrical conductivity. - Earth Planets and Space, 73, 3.
https://doi.org/10.1186/s40623-020-01339-3


Zitierlink: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5004860
Zusammenfassung
Vertical magnetic transfer functions (tippers) estimated at island observatories can constrain the one-dimensional (1-D) conductivity distribution of the oceanic lithosphere and upper mantle. This is feasible due to the bathymetry-dependent ocean induction effect (OIE), which originates from lateral conductivity contrasts between ocean and land and leads to non-zero tippers even for 1-D conductivity distributions below the ocean. Proper analysis of island tippers requires accurate three-dimensional (3-D) modeling of the OIE, for which so far was performed assuming constant sea water electric conductivity with depth. In this study, we explore—using rigorous 3-D electromagnetic modeling—to what extent realistic, depth-dependent, oceanic conductivity affects island tippers. The modeling is performed for 11 island observatories around the world in the period range 10−1 to 104 s. We also investigate the effect of seasonal variations of the oceanic conductivity and to which extent this could explain the observed systematic seasonal variation of tippers. Our model studies suggest that for most of the considered island observatories the effect from depth-varying oceanic conductivity is tangible and exceeds the error floor of 0.025, which usually is assigned to tippers during their inversion. The effect varies significantly with location, depending on regional bathymetry. Contrarily, the effects from seasonally varying oceanic conductivity were found to be too small to be worth consideration.