Brief Communication: Comparing ICESat-2 Altimetry and COSMO-SkyMed Synthetic Aperture Radar Interferometry Grounding Zone Products over Antarctica

Abstract. The grounding line represents a critical boundary in ice sheet dynamics, delineating the point at which an ice sheet detaches from its bed and begins to float as an ice shelf. Various methodologies have been developed to identify grounding lines, each leveraging distinct observational and processing techniques. However, there is a notable scarcity in the literature when it comes to comprehensive cross-comparisons of these different approaches. Here, we focus on a comparative analysis of a recent grounding line dataset derived from NASA’s ICESat-2 altimetry data and the COSMO-SkyMed (CSK) synthetic aperture radar (SAR) imagery provided by the Italian Space Agency (ASI), covering Antarctica between 2020 and 2021. Across 73 Antarctic glaciers spanning ~69,440 km of grounding line, we evaluate the landward limit of tidal flexure (F), break in slope (I_b), and inland hydrostatic limit (H). Results indicate an average discrepancy relative to DInSAR grounding lines of 177 ±325 meters (F), 40 ± 830 meters (I_b), and 4508 ± 2731 meters (H). Contrary to the expectation that F lies closest to the grounding line, the F-GL discrepancy exceeds the I_b – GL discrepancy, reversing the expected ranking (F< I_b <H). Our findings advocate for the continued development and cross-validation of diverse methodologies to enhance the precision of ice sheet boundary monitoring and improve understanding of Antarctic ice dynamics.