Toward a Baseline GIA Correction for Antarctica and Implications for East Antarctic Ice Mass Balance

New geochronological and geodetic constraints on GIA models for Antarctica have become considerably more sophisticated than they were a generation ago (CLIMAP-MAX through ICE-4G). The new generation of GIA models are critical to estimating and understanding ice mass changes at present-day. A correction needs to be made when using space gravity trends for ice mass balance assessments due to the fact that any vertical movements the solid Earth masquerade as changes in ice mass, and these must be carefully removed. The main upshot of the new Antarctic GIA models is a downward revision of negative ice mass trends deduced from the Gravity Recovery and Climate Experiment (GRACE), resulting from a reduced GIA correction. This revision places GRACE inferred trend in mass balance within the 1-s uncertainty of mass balance deduced by altimetry or by input-output methods (Shepherd et al., 2018). Uncertainties in both late-Holocene ice history and the regionalized low viscosity rheology beneath the West Antarctic Ice Sheet (WAIS) vex further improvement in predictions of present-day GIA gravity rate. A Bayesian method explores the gravimetric GIA trend over Antarctica, both withand withoutthe impact of a late Pleistocene Antarctic ice loads, along with the contribution of oceanic loads. We call this model without Antarctic loads a baseline for regional GIA models to build upon. We consider variations of the radial mantle viscosity profile and the volume of continental-scale ice sheets during the last glacial cycle. The modeled baseline GIA is mainly controlled by the lower mantle viscosity and continental levering caused by ocean loading. We find that the predicted baseline GIA correction to weakly depend on the ice history. This correction averages to +28.4 Gt/yr (a range of +16.5 to +41.9 at the 95% confidence level). Of special interest is the fact that the average GIA correction for East Antarctica is +23.6 ± 5.3. In contrast, with late-Pleistocene Antarctic-proximal ice included, the total modeled mass trend due to GIA is +73.7 (with a range of + 30.1 to +114.7) Gt/yr. We discuss the role of the baseline GIA for bounding present-day mass balance of the East Antarctic Ice Sheet during the space observing period after 1991.

is acknowledged.