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Abstract

Radar and laser satellite altimeters have been routinely monitoring the changes in surface elevation of the Greenland Ice Sheet since the early 1990s and 2000s, respectively. Radar and laser signals interact with the surface and sub-surface of the Greenland Ice Sheet in different ways depending on their wavelength and scattering properties of the illuminated firnpack, which vary both spatially and temporally. Here, we compare elevation changes observed by CryoSat-2’s radar and ICESat-2’s laser altimeters across the entire Greenland Ice Sheet between October 2018 and March 2022 to understand their similarities and differences. Averaged over the whole ice sheet, observed elevation changes from both CryoSat-2 and ICESat-2 altimeters agree very closely, with thinning rates of 15.3 ± 0.7 cm/yr and 12.7 ± 0.9 cm/yr, respectively. We perform an epoch to epoch comparison on the monthly elevation changes observed by both CryoSat-2 and ICESat-2 and find an average difference of -7.2 cm and a high correlation (R-value = 0.95) between them, demonstrating that both capture the same inter-annual variability in elevation changes over Greenland. This correlation is highest in the ablation zone of the ice sheet (R-value = 0.98), where the seasonal changes are most pronounced, with both altimeters capturing thinning and thickening due to surface melting in the summer and snowfall accumulation in the winter, respectively. Through this work, we aim to examine the suitability of producing an improved and merged record of Greenland elevation changes from radar and laser altimetry by improving the understanding of and resolving their residual differences.