Summary
Understanding basal processes across ice-sheet grounding lines is crucial in accurately modeling ice-sheet dynamics and estimating global sea-level rise. The grounding line, which demarcates the specific boundary between a grounded ice sheet and a floating ice shelf, is notoriously challenging to locate precisely. Existing methods for determining grounding line location rely on indirect methods, such as tide-induced vertical ice-shelf motion (the point of flexure determining the grounding line) and ice-surface slope change (the sharp change in gradient toward being flat indicating the grounding line). In this study, we use ice-penetrating radar (IPR) data to extract grounding line information from the LambertAmery glacier system. By incorporating ice bed topography and the reflection amplitude differences between ice-water and ice-bedrock interfaces, we establish an automated method to extract grounding line positions from radar survey lines. From 53 radar survey lines, we identified 85 grounding points. The comparison with the positions from an existing satellite InSAR-based grounding line product shows an average difference of 0.69 ± 0.70 km. Tidally-induced migration of grounding lines at different points of the tidal cycle, and advance/retreat of the grounding line with the evolution of the ice shelf, are the main reasons for the discrepancy between the radar-derived results and the existing grounding line products. In general, the results demonstrate the feasibility of IPR in confirming grounding line positions, and show great potential in constraining indirect satellite remote sensing or modeling evaluations at both regional and continental scales. Our work facilitates an ongoing effort of the Scientific Committee on Antarctic Research (SCAR)'s RINGS program to develop gapless coverage of bed topography in the coastal regions around Antarctica.
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