Crustal uplift in the Kerguelen Islands from Sentinel-1 InSAR : A consequence of recent ice melting?

The Kerguelen Islands (49°S, 69°E), a volcanic archipelago in the southern Indian Ocean, have experienced substantial environmental change over recent decades, including significant retreat of the Cook ice cap. The rapid ice loss is expected to induce measurable crustal deformation.

In this study, we use the complete archive of Sentinel-1 SAR imagery acquired since 2015 to examine the present-day deformation field of the Kerguelen Islands. Our small-baseline InSAR time-series analysis reveals a broad ~ 100 km-wide pattern of crustal uplift centered on the Cook ice cap, reaching up to ~ 6 mm/yr. 

To investigate the physical processes driving this uplift, we combine observed change in ice elevation inferred from multiple Digital Elevation Model over the 2015-2025 period with local estimates of shallow elastic properties derived from seismic experiments. Using a layered Cartesian elastic Earth model, we predict the surface deformation resulting from present-day unloading of the Cook ice cap, and compare model predictions to the InSAR-derived deformation field.

We then explore time-dependent deformation scenarios by considering viscoelastic deformation of the solid Earth induced by a range of plausible ice-loss histories over recent decades, and show that recent ice melting in the Kerguelen island can be used to place constraints on the rheology of the Earth’s upper mantle at decadal timescales. Finally, given the volcanic setting of the Kerguelen Islands, we also investigate whether magmatic sources could contribute to the observed long-wavelength uplift pattern.

Overall, this work highlights the potential of InSAR observations in remote subpolar environments to quantify ice-driven deformation and to infer solid Earth rheological properties on decadal timescales.