Velicogna I.*, J. Wahr*, C.Milly**, M.M.A. Shaltout***, A.R. ArRajehi****
*CIRES and Dept. of Physics, Univ. of Colorado, Boulder, CO 80309, USA; fax: 1.303.492.7935
**USGS and GFDL/NOAA, Princeton, NJ 08542-0308 USA
***National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt.
****Geophysics and Astronomy Institute, KA City for Science and Technology, Riyadh, Saudi Arabia.
Measurements from the GLAS laser altimeter aboard NASA's ICESAT satellite and from the NASA-DLR dedicated gravity satellite mission GRACE, both scheduled for launch in 2001 and both with expected lifetimes on the order of 5 years, can be combined to learn about ongoing changes in polar ice mass and viscoelastic rebound of the lithosphere under the ice sheet. GRACE will map the Earth's gravity field orders of magnitude more accurately and with considerably higher resolution than any existing satellite. GLAS will monitor changes in ice-sheet topography, and can provide estimates of secular changes in the total polar ice sheet mass over the lifetime of the mission. ICESAT/GLAS and GRACE can be combined to give better estimates of the ice sheet mass balance and post glacial rebound (PGR) than is provided by either observable by itself, but the improvement obtained by combining data would be substantially greater for multiple, successive missions. We will examine spatial resolution properties of the ice mass balance estimate, and the improvement of PGR estimates that would be provided by GPS measurements of vertical velocities.
|