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. Plain Language Summary Satellite altimeters transmitting 2.3 cm radio waves have been used to track changes in the shape of Earth's polar ice sheets since the late 1970s. In this study, we demonstrate the capability of a new altimeter mission—SARAL/AltiKa—to survey ice in western Antarctica using shorter, 0.8 cm radio waves. AltiKa measures changes in elevation across most of the ice sheet to within 0.6 cm/year of airborne and satellite sensors. Since the late 2000s, thinning of Thwaites Glacier has risen from 70 to 100 cm/year, but thinning of Pine Island Glacier has fallen from 128 to 117 cm/year. Key Points AltiKa elevation is 3.8 ± 0.5 and 2.5 ± 0.1 m higher than airborne laser altimetry and CryoSat‐2 AltiKa elevation changes are 0.6 ± 2.4 and 0.1 ± 0.1 cm/year lower than airborne laser and CryoSat‐2, so trends in penetration are minor Surface lowering at the Pine Island Glacier has fallen by 9% since the 2000s, while at Thwaites Glacier it has risen by 43%