The Potential of GOCE in Constraining the Structure of the Crust and Lithosphere from Post-Glacial Rebound
Glacial Isostatic Adjustment (GIA) due to Pleistocene glaeiation and deglaciation lias left clear imprints in the present-day geoid. The solid-earth models that are commonly used in simulating these geoid anomalies usually have the upper layer (crust/lithosphere) clastic. While this is a good approximation for oceanic litliosphere, it is over-simplified for many continental crustal areas, of which some are submerged at continental margins. At many places, these continental areas have a lower crustal zone that has low viscosities. Also at the top of the mantle (asthenosphere) such zones with low viscosities can exist.
Modeling results show that, due to their shallowness and due to the laterally non-homogeneous water load, these low-viscosity layers induce discernible signatures in the high-harmonic steady-state components of the geoid. These patchlike patterns have typical length scalcs ranging from about 100 – 1000 km, and typical magnitudes of 1 cm – 1 m, depending on, a.o., depth and width of the low-viscosity zone, viscosity and shoreline geometry.
Complications in correlating GIA modeling results with observed geoid anomalies might arise from uncertainties in isostatic corrections (topography and non-uniform composition of crust and litliosphere) and from other non-GIA related contributions to the observered anomalies. The characteristic forms of the patterns might assist in separating the various contributions to the observed geoid anomalies. This can be illustrated for the Adriatic coast of Italy, where the best fit to the spatial sca-levcl curve pattern is provided by a combination of GIA and regional plate tcctonics.
Keywordscrust geoid GOCE litliosphere low-viscosity solid-Earth zones post-glacial rebound shallow solid-Earth structure
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