Ice Sheet Elevation Change in West Antarctica From Ka-Band Satellite Radar Altimetry

Satellite altimetry has been used to track changes in ice sheet elevation using a series of Ku-band radars in orbit since the late 1970s. Here, we produce an assessment of higher-frequency Ka-band satellite radar altimetry for the same purpose, using SARAL/AltiKa measurements recorded over West Antarctica. AltiKa elevations are 3.8 ± 0.5 and 2.5 ± 0.1 m higher than those determined from airborne laser altimetry and CryoSat-2, respectively, likely due to the instruments' coarser footprint in the sloping coastal margins. However, AltiKa rates of elevation change computed between 2013 and 2019 are within 0.6 ± 2.4 and 0.1 ± 0.1 cm/year of airborne laser and CryoSat-2, respectively, indicating that trends in radar penetration are negligible. The fast-flowing trunks of the Pine Island and Thwaites Glaciers thinned by 117 ± 10 and 100 ± 20 cm/year, respectively, amounting to a 9% reduction and a 43% increase relative to the 2000s.