Estimation of Glacial Isostatic Adjustment uplift rate in the Totten glacier's outlet from GPS and GRACE

Glacial Isostatic Adjustment (GIA) refers to the gradual response of the solid Earth to the deglaciation of historic ice sheets.  This ongoing rebound is contributing to the measurements of gravity change and land deformation, respectively, by Gravity Recovery And Climate Experiment (GRACE) and Global Positioning System (GPS).  When these space geodetic data are used to quantify the present-day ice mass change, the effect such as GIA must be accounted for.  In this study, we developed a method to estimate GIA and elastic deformation by the present-day ice mass change in the GPS time series with the example of Casey station in East Antarctica.  We determined a high-resolution, present-day ice mass change model on the outlet of Totten Glacier and calculated the elastic rebound over the area.  Our high-resolution model indicated a total mass loss of 15.7 ± 0.5 Gt/yr on the outlet of Totten Glacier from 2002 to 2017 with the accelerated loss in the last half of the period.  We estimated the viscoelastic deformation attributed to GIA by removing the predicted elastic deformation from GPS measurements.  Four different GPS position solutions for the Casey station, the continuously operating GPS station near the area, were examined.  The estimated GIA signal appears to be within 0.3 – 1.3 mm/yr which shows its contribution on the vertical deformation between 30 – 60 % among different GPS solutions.  On the other hand, the vertical elastic deformation trend is predicted to be 0.7 mm/yr from the ice mass change model.  The GPS measured seasonal variation is explained equally by atmospheric-oceanic loading and degree-1 loading with a couple mm amplitude in vertical time series.  The elastic rebound from the present-day ice mass change also perturbed the horizontal displacement by 0.13 mm/yr in west and 0.21 mm/yr in north directions.  This is in the opposite to the plate motion of the East Antarctica around the Casey station and amounts approximately up to 10 % of the measured tectonic motion.