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Geodesy and the Problem of Ice Sheets

  • I. Velicogna
  • J. Wahr
Part of the International Association of Geodesy Symposia book series (IAG SYMPOSIA, volume 127)

Abstract

In recent years, great improvements have been made toward understanding the modern dynamics and recent history of the ice sheets. Several recently-launched satellite missions promise to make geodesy the most powerful tool for investigation of the changing ice sheets, including their past history and their present behavior. Mathematical description of ice sheet behavior from geodetic data requires accurate modeling of all the processes which may affect the measurements. Most geodetic tools measure changes in elevation of the ice sheets, which can include Post Glacial Rebound (PGR), the current Ice Mass Trend (IMT) consisting of both accumulation and glacial outflux, and processes of compaction within the firn column. Consequently it is necessary for mathematical models of geodetic data to separate the effects of IMT, PGR, and compaction. Satellite measurements of the time-variable geoid are insensitive to compaction effects and depend on IMT and PGR differently than do height measurements. Two methodological approaches have been proposed to separate these effects using measurements of height and time-variable geoid: 1- direct inversion for ice mass variability (Wu et al., 2002), which requires a priori assumptions about either the Earth’s rheology or the ice load history; 2- iterative solution for the fields, which theoretically is more approximate but is computationally much simpler and less dependent on a priori assumptions. In this paper we analyze how we can learn about IMT and PGR by combining geodetic measurements, and we assess the conditions required to optimally combine satellite and ground-based data sets.

Keywords

Post Glacial Rebound Geoscience Laser Altimeter System Compaction Trend Compaction Error Geoscience Laser Altimeter System Data 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Bentley, C.R., and M.B. Giovinetto, Mass balance of Antarctica and sea level change, in Proceedings of the international Conference on the Role of the Polar Regions in Global Change, 1990, edited by G. Weller, C.L. Wilson, and B.A. B. Seeverin, pp. 481–488, Univ. of Alaska, Fairbanks, 1991.Google Scholar
  2. Boville, B. A., and P. Gent, The NCAR climate system model, version one, J. Clim., 11, 1115–1130, 1998.CrossRefGoogle Scholar
  3. Dietrich, R., Present Status of the SCAR GPS Epoch Campaigns, SCAR Report no. 20, 15–18, 2001.Google Scholar
  4. Han, D. and J. Wahr, The viscoelastic relaxation of a realistically stratified Earth, and a further analysis of post-glacial rebound, Geophys. J. Int., 120, 287–311, 1995.CrossRefGoogle Scholar
  5. Jekeli, C., Alternative methods to smooth the Earth’s gravity field, Rep. 327, Dept. of Geod. Sci. and Surv., Ohio State Univ., Columbus, 1981.Google Scholar
  6. Mitrovica, J.X., J.L. Davis, and I.I. Shapiro, A spectral formalism for computing three-dimensional deformations due to surface loads, 1, Theory, J. Geophys. Res., 99, 7057–7073, 1994.CrossRefGoogle Scholar
  7. Oerter, H., Wilhelms, F., Jung-Rothenhäusler, F., Göktas, F., Miller, H., Graf, W., Sommer, S., Accumulation rates in Dronning Maud Land, Antarctica, as revealed by dielectric-profiling measurements of shallow firn cores, Annals of Glaciology, 30, 27–34, 2000.CrossRefGoogle Scholar
  8. Raymond, C. A., E. R. Ivins, T. S. James and M. Heflin, The role of geodesy in assessing the state of the West Antarctic Ice Sheet. West Antarctic Ice Sheet Chapman Conference, 1998.Google Scholar
  9. Velicogna, I., and J. Wahr, A method for separating Antarctic post-glacial rebound and ice mass balance using future ICESat Geo-science Laser Altimeter System, Gravity Recovery and Climate Experiment, and GPS satellite data, J. Geophys. Res. Vol. 107, 10.1029/2001JB000708, 2002a.Google Scholar
  10. Velicogna, I., and J. Wahr, Post Glacial rebound and Earth’s Viscosity Structure From GRACE, In Press J. Geophys. Res. Vol. 107, 10.1029/2001JB001735, 2002b.Google Scholar
  11. Wahr, J.M., D. Han, and A. Trupin, Predictions of vertical uplift caused by changing polar ice volumes on a visco-elastic Earth, Geophys. Res. Lett., 22, 977–980, 1995.CrossRefGoogle Scholar
  12. Wahr, J., M. Molenaar, and F. Bryan, Time-Variability of the Earth’s Gravity Field: Hydrological and Oceanic Effects and Their Possible Detection Using GRACE, J. Geophys. Res., 103, 30,205–30, 230, 1998.Google Scholar
  13. Wahr, J., D. Wingham, C.R. Bentley, A method of combining GLAS and GRACE satellite data to constrain Antarctic mass balance,. J. Geophs. Res., 105, 16,279–16, 294, 2000.Google Scholar
  14. Wingham, D.J., Small fluctuations in the density and thickness of a dry firn column J. Glaciol., 46, 399–411, 2000.CrossRefGoogle Scholar
  15. Wu, X., Watkins, M., Ivins, E., Kwok, R., Wang, P.; Wahr, J., Toward global inverse solutions for current and past ice mass variations: Contribution of secular satellite gravity and topography change measurement, J. Geophys. Res., 107, 2001JB000543, 2002.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • I. Velicogna
    • 1
  • J. Wahr
    • 1
  1. 1.Dept. of ColoradoCIRES, Univ. of ColoradoUSA

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