Abstract
NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) laser
altimeter launched in Fall 2018, providing an invaluable addition to the
polar altimetry record generated by ESA’s CryoSat-2 radar altimeter. The
simultaneous operation of these two satellite altimeters enables unique
comparison studies of sea ice altimetry, utilizing the different
frequencies and profiling strategies of the two instruments. Here, we
use freeboard data from ICESat-2 to assess Antarctic snow freeboard
retrievals from CryoSat-2. We first discuss updates made to a
previously-published CryoSat-2 retrieval process and show how this
Version 2 algorithm improves upon the original method by comparing the
new retrievals to ICESat-2 in specific along-track profiles as well as
on the basin-scale. In two near-coincident along-track profiles, we find
mean snow freeboard differences (standard deviations of differences) of
0.3 (9.3) and 7.6 cm (9.6 cm) with 25 km binned correlation coefficients
of 0.77 and 0.89. Monthly mean freeboard differences range between -2.9
(10.8) and 6.6 cm (16.8 cm) basin wide, with the largest differences
typically occurring in Austral fall months. Monthly mean correlation
coefficients range between 0.57 and 0.80. While coincident data show
good agreement between the two sensors, they highlight issues related to
geometric and frequency sampling differences that can impact the
freeboard distributions.