Electromagnetic Induction by Ocean Currents and the Conductivity of the Oceanic Lithosphere

Abstract

The principles of electromagnetic induction in the earth by ocean currents are reviewed with an emphasis on their interaction with the conducting earth and their modal structure. This is illustrated theoretically by examining a Kelvin wave off of the California coast and experimentally by separating seafloor measurements into ionospheric and oceanic parts. An attempt is made to estimate the electrical conductivity of the oceanic lithosphere from the polarization of the magnetotelluric fields near coastlines, yielding an upper limit of 0.001S/m. Possible interpretations of this value in terms of local current channeling are discussed.