Paul Tregoning (Australian National University, Canberra, Australia), will present

“A tool to assess the accuracy of glacial isostatic adjustment predictions of present-day crustal uplift rates”

While there are many global and regional glacial isostatic adjustment (GIA) models available that can be used to compute expected present-day uplift rates of the surface of the Earth, they do not always agree in their predictions. Obtaining accurate estimates of uncertainties in predictions is difficult due to the assumptions that must be made when constructing the GIA models, and geodetic users often simply adopt a preferred model or assign uncertanties based on the spread of values derived from several models. Here we show that, through a combination of gravity changes observed by GRACE/GRACE-FO and uplift observed by GNSS, it is possible to quantify the error in uplift rates of one or more GIA models. Whilst it is not possible to repair the GIA models directly, this tool can be used to identify regions where ice histories and/or Earth rheology parameters are deficient in the GIA models. In this talk I will give examples of locations where GIA modelling appears to be very accurate as well as indicate some locations that are clearly problematic.