Surface Mass Balance Variability causes Viscoelastic Solid Earth Deformation in the Antarctic Peninsula

Present-day ice-mass changes in Antarctica deform the solid Earth elastically, and this signal needs removing from GPS observations of displacement before they can be used to constrain models of glacial isostatic adjustment (GIA). However, much of West Antarctica is underlain by weak upper mantle, meaning that these short-term fluctuations may also cause a transient or viscous deformation of the Earth. We model the viscoelastic response of the solid Earth to surface mass balance (SMB) variability in the Antarctic Peninsula and find an improved fit to GPS data at most sites compared to elastic only. Viscoelastic modelling constrains upper mantle steady-state viscosity in the northern Peninsula to 5×10¹⁷ to 2×10¹⁸ Pa s, and >1×10¹⁸ Pa s for the mid to southern Peninsula. In the northern Peninsula, removing viscoelastic displacement caused by SMB variability from GPS time series increases estimated uplift rates by up to 3mm/yr compared with using an elastic correction.