PRESENT-DAY ANTARCTIC ICE MASS CHANGES AND CRUSTAL MOTION

The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic ice sheet mass balance are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak Antarctic vertical velocities of the ICE-3G glacial rebound model, which are in excess of 20 mm/a. Lf the Holocene Antarctic deglaciation history portrayed in ICE-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(21) Pa . s, then a vast geographical region in West Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean mass exchange is large enough to account for a substantial portion of the observed secular polar motion (Omega ($) over right arrow m) and time-varying zonal gravity field J(l).