  During the propagation of a tsunami, gravity and sound waves can be produced,
spreading from its source to the ionosphere's upper layers, thus generating
perturbed electron densities in its E and F regions. These ionospheric
disturbances can be studied in detail using measurements of the ionosphere's
Total Electron Content (TEC), registered by permanent GNSS stations. In this
contribution, the foundations of the VARION method (Variometric Approach for
Real-time Ionosphere Observation) are described in order to obtain TEC's
temporal variations with the aim of detecting such ionospheric disturbances.
Moreover, the numerical results obtained after applying this method to real
cases of tsunamis monitored by those satellites whose Ionospheric Pierce Points
(IPPs) are closest to the tsunami source are presented. Lastly, based on these
ionospheric perturbations reflected in the signals emitted by the satellites, a
preliminary design is described for its potential integration into a Tsunami
early Warning System (TWS) for the Iberian Peninsula.
