Comparison of recent multi mission elevation change rates of Greenland and Antarctica

Mass changes of the polar Ice Sheets and their contribution to global mean sea level is an essential climate variable, critical for adaptation planning and important to understand the earth system in a warming climate. To ensure long term continuation of ice elevation and change records ESA proposed the Copernicus Polar Ice and Snow Topography Altimeter mission (CRISTAL) to be launched in 2027. CRISTAL, for the first time, will carry a dual-frequency altimeter in Ku and Ka Band to monitor changes in the height of ice sheets and glaciers and thickness of and snow on sea ice. Therefore, with the upcoming CRISTAL mission it is absolutely necessary to focus on sensor specific characteristics and its impact on elevation change records beforehand. To tackle these questions, we determine surface elevation change rates with a focus on the last decade of laser and radar altimetry observations using ICESat2, CryoSat-2, Sentinel-3 and SARAL/Altika. We investigate ice sheet wide and regional differences of elevation change rates derived from the four missions in the period from 2019 to 2022 with focus on different sensor characteristics (Laser/Ku/Ka Band), different acquisition/processing strategies ((P)LRM, SAR, SARIn), retracking (TFMRA,ICE1,ICE2) and orbit geometry (81.5°/88°).

Our findings show that trend estimates of individual missions diverge most strongly at the margins and areas of complex topography but also in the flat interior of ice sheets and are highly dependent on the choice of retracker. We show that in order to determine volume changes as consistently as possible across missions, a uniform processing is required that includes backscatter/leading edge correction to suppress the influence of time-varying radar penetration due to changes in volume scattering.