The STSE_GLITter project produced an updated measurement of the grounding line location, and ice thickness at the grounding line from CryoSat-2 radar altimetry data. Grounding lines mark the boundary between floating and grounded sections of a marine terminating ice sheet. They are a sensitive indicator of ice sheet stability and, when migration occurs, can indicate the influence of changes in the local environmental forcing. Monitoring changes in grounding line positions allows regions of instability to be identified, and such measurements are a valuable reference for assessing the fidelity of ice dynamical models. The grounding line lies at the landward edge of a zone where ice shelf flexure occurs as a consequence of ocean height variations, for example due to tidal displacement, the inverse barometer effect, and oceanic circulation variability. Although grounding lines cannot be directly observed because they lie at the base of the ice sheet, their surface expression - the hinge line - can be detected using a range of in situ and remote-sensing techniques.

The GLITter project developed a method for detecting grounding line locations as the break in ice sheet surface slope, computed from CryoSat-2 elevation measurements using a plane-fitting solution. In addition, the project also developed an estimate of ice thickness at the grounding line assuming the ice was floating in hydrostatic balance. These techniques were employed to derive measurements in four topographically diverse sectors of Antarctica - Filchner-Ronne Ice Shelf, Ekström Ice Shelf, Amundsen Sea sector, and the Larsen-C Ice Shelf. A comparison of the with independent measurements of the hinge line location determined from differential SAR interferometry shows good overall agreement between techniques, with a mean separation of 4.5 km.

Although CryoSat-2 and SAR interferometry are complementary tools for mapping the grounding line locations, only a handful of glaciers grounding lines have been mapped on more than one occasion (see Figure 1). Because measurements of grounding line migration are a key indicator of ice sheet stability, a systematic approach to tracking grounding line positions remain a key observational and knowledge gap.