HR: 0800h
AN: G31C-0806    [Abstracts]
TI: Sensitivity of GIA Models With a Low-Viscosity Earth Layer to the Ice-Load History in Relation to the Resolving Power of GOCE
AU: Schotman, H H
EM: hugo@deos.tudelft.nl
AF: DEOS - Delft University of Technology, Kluyverweg 1, Delft, 2629 HS Netherlands
AU: Schotman, H H
EM: hugo@deos.tudelft.nl
AF: SRON National Institute for Space Research, Sorbonnelaan 2, Utrecht, 3584 CA Netherlands
AU: * Vermeersen, B L
AF: DEOS - Delft University of Technology, Kluyverweg 1, Delft, 2629 HS Netherlands
AB: The GOCE satellite mission, which is planned by ESA for launch in 2006, is designed to map the static global gravity field with centimeter accuracy in geoid height at a resolution of about 100 kilometer. Features in such a high resolution gravity field can be associated with geophysical processes that act on a regional scale, as the response of shallow low-viscosity layers to loading and unloading of the crust in glacial isostatic adjustment (GIA). In GIA studies it is generally assumed that continental lithosphere has very high viscosity and is therefore effectively elastic. It can be expected however that parts of the lower crust have low viscosity. In a recent study we have shown that such a crustal low-viscosity zone (CLVZ) introduces variations in geoid height up to 1 meter with spatial scales down to hundred kilometers underneath and just outside formerly glaciated areas. We have shown that the response is sensitive to both changes in the properties of the CLVZ and the ice-load history. In this study we will further investigate this sensitivity by using two existing ice-load histories. To investigate the depth-dependence of the sensitivity, we will also compute the response for an asthenospheric low-viscosity zone (ALVZ) just below the lithosphere. We will show, using degree amplitudes, that for a CLVZ the differences are above the expected GOCE performance up to degree 120 and for an ALVZ up to degree 60. The latter is also true for the realized GRACE performance (GGM01C). This means that GRACE, but especially GOCE, might be able to provide information on the ice-load history in the presence of an LVZ. To extract information about the LVZ from the degree amplitudes, we show that it is possible to partly remove the influence of the ice-load history and thus compute spectral signatures for different properties of the LVZ. We will focus on the continental shelf-areas of western Europe and eastern North America to show the sensitivity to the inclusion of an LVZ of GIA corrections to estimates of present-day sea level rise.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8159 Rheology--crust and lithosphere
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1234 Regional and global gravity anomalies and Earth structure
DE: 1236 Rheology of the lithosphere and mantle (8160)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting