Reply on RC1

Abstract

Antarctic digital elevation models (DEMs) are essential for human fieldwork, ice motion tracking and the numerical modelling of ice sheet. In the past thirty years, several Antarctic DEMs derived from satellite data have been published. However, these DEMs either have coarse spatial resolutions or aggregate observation spanning over several years, which limit their further scientific applications. In this study, the new-generation satellite laser altimeter Ice, Cloud, And Land Elevation Satellite-2 (ICESat-2) is used to generate a new Antarctic DEM for both the ice sheet and ice shelves. Approximately 4.69 × 109 ICESat-2 measurement points from November 2018 to November 2019 are used to estimate surface elevations at resolutions of 500 m and 1 km based on a spatiotemporal fitting method. Approximately 74 % of Antarctica is observed, and the remaining observation gaps are interpolated using the ordinary kriging method. The DEM is formed from the estimated elevations in 500 m and 1 km grid cells, and is finally posted at the resolution of 500 m. National Aeronautics and Space Administration Operation IceBridge (OIB) airborne data are used to evaluate the generated Antarctic DEM (hereafter called the ICESat-2 DEM) in individual Antarctic regions and surface types. Overall, a median bias of 0.03 m and a root-mean-square deviation of 15.64 m result from approximately 5.2 × 106 OIB measurement points. The accuracy and uncertainty of the ICESat-2 DEM vary in relation to the surface slope and roughness, and more reliable estimates are found in the flat ice sheet interior. The ICESat-2 DEM is superior to previous DEMs derived from satellite altimeters for both spatial resolution and elevation accuracy and comparable to those derived from stereo-photogrammetry and interferometry. Similar results are found when comparing to elevation measurements from kinematic GNSS (GPS and the Russian GLONASS) transects. The elevations of high accuracy and ability of annual update make the ICESat-2 DEM an addition to the existing Antarctic DEM groups, and it can be further used for other scientific applications. The generated ICESat-2 DEM (including the map of uncertainty) can be downloaded from National Tibetan Plateau Data Center, Institute of Tibetan Plateau Research, Chinese Academy of Sciences at https://data.tpdc.ac.cn/en/disallow/9427069c-117e-4ff8-96e0-4b18eb7782cb/ (Shen et al., 2021, DOI: 10.11888/Geogra.tpdc.271448).