PRESENT-DAY ANTARCTIC ICE MASS CHANGES AND CRUSTAL MOTION

The peak vertical velocities predicted by three realistic, but contras ting, present-day scenarios of Antarctic ice sheet mass balance are fo und to be of the order of several mm/a. One scenario predicts local up lift 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 deglaciati on history portrayed in ICE-3G is realistic, and if regional upper man tle 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 th at could be detected by a future Global Positioning System (GPS) campa ign. While present-day scenarios predict small vertical crustal veloci ties, their overall continent-ocean mass exchange is large enough to a ccount for a substantial portion of the observed secular polar motion (Omega ($) over right arrow m) and time-varying zonal gravity field J( l).