A novel theoretical framework to estimate GIA from GPS and GRACE

Glacial Isostatic Adjustment (GIA) is the visco-elastic response of the Solid Earth to changes in the ice sheet load during past glacial cycles. GIA produces vertical land motion and mantle mass redistribution, both of which are important to include when studying surface deformations, sea level rise, present day mass changes from satellite data and changes in the geoid. Estimates of GIA are typically obtained from forward numerical models that are driven by varying assumptions about Earth rheology and ice load history, leading to a range of GIA estimates. As a consequence, many studies are trying to move away from forward modelling and co-estimate GIA from contemporary observations. We present a novel theoretical framework that uses GPS vertical land motion and GRACE data to provide a data-driven estimate of GIA. Assuming that all other significant processes are correctly identified and accounted for, we show that GRACE and GPS data can successfully be used together to isolate GIA. We compare our results to outputs from various GIA forward models.