Voltage measurements over the CAM-1 submarine cable between Madeira Island and Portugal mainland

Data of electrical voltage measured between the ends of the CAM-1 cable, during fifteen months, have been analysed in order to determine the electrical stability of the cable and to obtain some preliminary information related to water transport. The monthly average of the potential measured during days with low geomagnetic activity suggests a periodicity of 120 days that was tentatively interpreted as having origin in water flow. These results show a small trend that is compatible with no drift in the cable. The mean electric field estimated from quiet days is 0.206 ± 0.022 mV/km. If the variations of this potential are attributable to ocean water transport a total water flow of ±0.09 cm/s is estimated. This value represents a maximum value for temporal variations of the spatially averaged water-flow velocity.