High-Harmonic Geoid Signatures due to Glacial Isostatic Adjustment, Subduction and Seismic Deformation

GOCE is expected to increase our knowledge of the higher spherical harmonics of the quasi-static geoid, with "higher" being in the range of about harmonic degree 50 (half-wavelength 400 km) to harmonic degree 250 (halfwavelength 80 km). One of the major challenges in interpreting these high-harmonic (regional-scale) geoid signatures in GOCE solutions will be to discriminate between various solid-earth contributions. Here, emphasis will be placed on three major contributors: remaining deviations from isostasy due to late-Pleistocene ice ages; shallow upper mantle subduction of oceanic lithosphere; and accumulated deformation due to sequences of large earthquakes. However, there are many more possible high-harmonic (shallow) solid-earth contributions, including uncertainties related to isostasy of a chemically and stratigraphically heterogeneous crust and lithosphere; tectonic processes like mounting building, continental plateau and oceanic basin formation; and high-harmonic signatures related to shallow mantle density variations and mantle-based processes as plumes. Discrimination between all these various causes might be accomplished by combining the geoid signal with other (space-)geodetic observables, geological data, seismic models and by 2-D pattern matching.