Assessment of CryoSat-2 Baseline-D Height Product by GNSS and ICESat-2 in Lambert-Amery System, East Antarctica

Abstract

CryoSat-2 repeatedly collects dense radar altimetry footprints covering high latitudes of the polar ice sheets for over 10 years. The Baseline-D height product of CryoSat-2 was recently upgraded and released in 2019. Based on the internal or locally external evaluation of CryoSat-2 Baseline-D ice heights, we extended the validation both heterogeneously and spatially to accomplish a comprehensive assessment. Firstly, reliable ice surface GNSS point solutions along the 36th Chinese National Antarctic Research Expedition traverse functioned as a height reference for comparison with the CryoSat-2 SAR synthetic aperture radar interferometric mode (SIN) data. Secondly, the Land Ice Along-Track Height product over Lambert-Amery System (LAS) from ICESat-2, was also applied to validate CryoSat-2 SIN and Low-Resolution Mode (LRM) data. As the results indicate, the SIN height accuracy is evaluated to be -1.68 m ± 2.35 m (slope < 0.65°) along the traverse and -0.96 ± 1.95 m (slope < 0.95° & roughness < 3 m) over the margin of LAS. The LRM height accuracy is evaluated to be -0.13 ± 0.46 m (slope < 0.1° & roughness < 1 m) over the interior of LAS. The standard deviation (SD) of the height differences degrades linearly against the limited growth of the terrain slope/roughness at the confidence level of 99%. It is worth noting that the spatially heterogeneous pattern of height differences is correlated with surface topography variations. This study should imply the potential to improve the estimation of mass balance and its uncertainty of polar ice sheets based on radar altimetry data.

Identification and Activity of Subglacial Lakes Beneath the Mercer and Whillans Ice Streams and Slessor Glacier

“…Here, we generate the time series of the ice surface elevation changes over seven subglacial lakes (four known subglacial lakes with reestimated outlines: LSLC, LSLM, SLW, and L12; three new discovered subglacial lakes: MWIS1, MWIS2, and MWIS3) from the CryoSat-2 SARIn data (2010-2020) and the ICESat-2 data (2018-2021). We note that different instrument characteristics, accuracy, and data distribution of CryoSat-2 and ICESat-2 altimetry can lead to biases in the time series values derived from the different datasets [45], [46]. In a previous study, it was noted that the mean and RMS of the biases between the ICESat-2 and CryoSat-2-based time series were less than 0.3 m and 0.5 m, respectively, in most subglacial lake regions within our study regions [22].…”