Magnetotellurics with geomagnetic observatory data influenced by the ocean effect: upper mantle conductivity under the islands of Gan and Tristan da Cunha

Achim Morschhauser1, Alexander Grayver2, Alexey V Kuvshinov2, Friedemann Samrock2 and Juergen Matzka3, (1)Deutsches GeoForschungsZentrum GFZ, Potsdam, Germany, (2)ETH Swiss Federal Institute of Technology Zurich, Institute of Geophysics, Zurich, Switzerland, (3)GFZ German Research Centre for Geosciences, Potsdam, Germany