Horizontal GIA Velocities and ReferenceFrame Determination

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Horizontal GIA Velocities and Reference-Frame
Determination

• Jim Davis, Mark Tamisiea, and Tom Herring

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Following Slides

• GIA deformations calculated in CE frame
  (standard)
• GIA deformations after rotation that establishes
  reference frame

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Conclusions

• GIA may introduce a systematic error in rotation
  of 1 mm/yr
• We need a greater density of GPS sites in
  GIA-deforming regions (but sensitive to
  ice-model errors)
• Radial motions perhaps more important, but we
  still require a greater site density in these
  areas (also see Mark Tamisieas presentation)
• We need to extend suite of Earth models for which
  we have the viscoelastic Greens functions.
• We probably need to make the western site
  cutoff for SNARF farther east than for this
  solution.

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Recommendations

• SNARF group needs to have working standard
  solution
• Sites well distributed
• Well on stable NA
• Velocities and covariances

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