Vertical deformation in Greenland: separation of past and present-day ice mass loss contributions

We compute daily GPS solutions for about 200 permanent stations in Greenland, Scandinavia and Canada for the 2000 – 2023 period, using the CNES/GINS software in precise point positioning with integer ambiguity resolution (IPPP) mode. The observed vertical displacements are caused by both past- and present-day ice mass (PDIM) changes. The glacial isostatic adjustement (GIA) is the visco-elastic Earth’s response to the Pleistocene glaciation and deglaciation, whereas the PDIM is often estimated assuming an elastic Earth’s response.

We revisit the problem of the separation of GIA and PDIM using state-of-the-art ice models (for example, ICE-6G and ICE-7G) and observations from space gravimetry (GRACE and GRACE Follow On) and altimetry (CryoSat-2 and ICESat-2).

In particular, we investigate different rheology models, including the classical Maxwell model used in GIA modeling, but also the Burgers model allowing transient anelastic deformation at timescales of 10 to 20 years.

We found that the Burgers model with a transient viscosity of about 10¹⁸ Pa.s in the upper mantle, combined with the VM5a or VM7 viscosity profiles (Maxwell component) is in better agreement with the observed GPS vertical displacements.