HR: 16:30h
AN: G34A-03    [Abstracts]
TI: Estimating Geocenter Variations by Combining GRACE and GPS Data Sets
AU: * Elosegui, P
EM: pelosegui@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 United States
AU: * Elosegui, P
EM: pelosegui@cfa.harvard.edu
AF: Institut Estudis Espacials Catalunya/CSIC, Gran Capita 2, Barcelona,, 08034 Spain
AU: Davis, J L
EM: jdavis@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 United States
AU: Mitrovica, J X
EM: jxm@physics.utoronto.ca
AF: University of Toronto, Department of Physics, 60 St. George Street, Toronto, Ontario,, M5S 1A7 Canada
AU: Tamisiea, M E
EM: mtamisiea@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 United States
AB: Understanding the motion of the geocenter is important since these link the underlying motions of a kinematic reference frame defined by site positions and velocities to ongoing dynamics of the Earth system. On seasonal timescales, redistribution of surface water dominates the variation of the geocenter. GRACE gravity field estimates, in contrast to observations from techniques such as SLR, DORIS and GPS, are insensitive to geocenter variations and thus cannot be used alone to determine the seasonal component of these variations. However, the loading associated with this mass redistribution also causes surface deformation, to which the positional space geodetic techniques are sensitive. This sensitivity to deformation defined in two different reference frames, geometric in GPS and geodynamic in GRACE, suggests a new approach for determining and understanding motions of the geocenter. Analysis of results based on combining GPS and GRACE estimates for South America, where the vertical loading signature is $\sim\pm10$~mm, indicates that the annual geocenter variation can be estimated with an accuracy of $\pm2$~mm. A global analysis has the potential to significantly improve this accuracy. We will present such a global analysis and discuss the advantages and limitations of this new methodology.
DE: 1206 Crustal movements--interplate (8155)
DE: 1214 Geopotential theory and determination
DE: 1229 Reference systems
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting