Glacial isostatic adjustment (GIA) describes the delayed solid Earth’s response to changing ice masses and is mandatory to quantify the recent ice-mass loss in Antarctica. Furthermore, GIA as a dynamic process affects the stability of the Antarctic Ice Sheet (AIS). The most prominent marine ice sheet instability (MISI) involves the feedback between ice, ocean and solid earth and is charged for a future global mean sea-level rise of 65 cm by the Thwaites glacier (West Antarctica) alone. GIA acts here as a stabilising mechanism, which is controlled by the upper-mantle viscosity. However, GIA in Antarctica suffers from an imprecise knowledge of its viscosity structure. Thus, investigating the role of GIA for future sea-level projections of the AIS requires substantial improvements in the modelling of GIA.

A realistic modelling of the GIA signal in different regions of Antarctica demands specific constraints on the Earth’s interior as well as on past and recent glacial changes. These have to be based on geodetic observations. The Antarctic-wide GNSS data product of the GIANT-REGAIN project led by TU Dresden in combination with recently improved laterally heterogeneous Antarctic Earth structures provided by GFZ will allow us to narrow down the uncertainty of GIA model outputs substantially, and to resolve previous inconsistencies using GNSS observations.

We will combine the different expertise of our groups in realising/analysing in-situ observations and in performing advanced GIA modelling in a joint effort. We will exploit the quality and quantity of the proposed geodetic and geophysical observational data (a) on bedrock displacements measured by GNSS and (b) on the structure and rheology of the Antarctic lithosphere and mantle. In addition to analyses for the entire continent, we will focus on the Amundsen Sea Embayment (West Antarctica) and the Indian Sector (East Antarctica). In this respect, a major aim is to assess the uncertainty space regarding the controlling parameters as well as to identify remaining caveats in the modelling of GIA, e.g., the effect of a transient rheology or the impact of a Holocene re-advance of parts of the AIS.