Surface Deformation due to Non-Linear Tides in the North Sea

The indirect deformations of the Earth caused by variations in the surface load from non-linear tides are detectable by measuring e.g. surface displacements, tilt or gravity changes. To predict these shallow water loading deformations, an ocean tide model (describing the spatial and temporal distribution of the surface load) and a visco-elastic Earth model (describing how the Earth responds to the surface load) are needed. The ongoing satellite altimetry missions have improved considerably to model these effects. In this study, we use Topex/Poseidon (T/P) data to construct a model of the shallow water loading deformations at the third-diurnal and higher frequency tidal band. Furthermore, we compare our T/P results with vertical surface deformation observed using GPS at some selected locations in the coastal region of the North Sea.