Comparing geodetic observations to GIA models
Abstract
Geodetic observations of global deformation and gravity changes have improved greatly over the last decade. These solutions give better insight into the long-term deformation of the earth and provide additional constraints on GIA models. In this talk, we discuss the issues that can arise in comparing the longest-wavelength components (the lowest-degree spherical harmonics) of GIA solutions with geodetic observations (e.g., GRACE, altimetry, GNSS, SLR, and tide gauges). In generating global geodetic solutions, many processing techniques and conventions can affect the longest-wavelength components. For example, GNSS and altimetry solutions must be realized in an ITRF solution. Errors in this realization can introduce apparent geocenter motion. The importance of these errors was illustrated by Beckley et al., GRL, 2007, who demonstrate that when altimetry solutions were changed from the ITRF2000 to the ITRF2005 reference frame, regional estimates of sea surface height exhibited differences of up to 1.5 mm/yr. Issues can also exist on the GIA modeling side. When comparing to or correcting GRACE data, a GIA geoid prediction generated by a model that includes rotational feedback must not include the direct component of the shift in the orientation of the centrifugal potential. Including this component can result in an approximate factor-of-two overestimate of the spherical harmonic degree-2, order-1 coefficients. We will discuss difficulties that can arise with regard to mass conservation (degree-0), geocenter motion (degree-1), and polar motion (degree-2, order-1) when comparing GIA model solutions to data.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.G23C..01T
- Keywords:
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- 1217 GEODESY AND GRAVITY / Time variable gravity;
- 1229 GEODESY AND GRAVITY / Reference systems;
- 1239 GEODESY AND GRAVITY / Earth rotation variations