Abstract
Abstract. Accurate information of ice sheet surface slope is essential for estimating elevation change by satellite altimetry measurement. A study is carried out to recover surface slope of Antarctic ice sheet from Ice, Cloud and land Elevation Satellite (ICESat) elevation measurements based on repeat orbits. ICESat provides repeat ground tracks within 200 meters in cross-track direction and 170 meters in along-track direction for most areas of Antarctic ice sheet. Both cross-track and along-track surface slopes could be obtained by adjacent repeat ground tracks. Combining those measurements yields a surface slope model with resolution of approximately 200 meters. An algorithm considering elevation change is developed to estimate the surface slope of Antarctic ice sheet. Three Antarctic Digital Elevation Models (DEMs) were used to calculate surface slopes. The surface slopes from DEMs are compared with estimates by using in situ GPS data in Dome A, the summit of Antarctic ice sheet. Our results reveal an average surface slope difference of 0.02 degree in Dome A. High resolution remote sensing images are also used in comparing the results derived from other DEMs and this paper. The comparison implies that our results have a slightly better coherence with GPS observation than results from DEMs, but our results provide more details and perform higher accuracy in coastal areas because of the higher resolution for ICESat measurements. Ice divides are estimated based on the aspect, and are weakly consistent with ice divides from other method in coastal regions.
Highlights
Slope and aspect of Antarctic ice sheet are important parameters for Antarctic drainage divides, glacier movement, morphometric measurements, and many other studies
The surface slopes of Antarcitc ice sheet reveal some subtle features, such as ice divides and Lake Vostok, where the slopes are mostly
Slope calculated by the repeat tracks in this paper performs well near the satellite tracks, but the method may not be appropriate for the areas far away from the tracks, which results in the blank gaps between different tracks in figure 3
Summary
Slope and aspect of Antarctic ice sheet are important parameters for Antarctic drainage divides, glacier movement, morphometric measurements, and many other studies. National Snow and Ice Data Center (NSIDC) developed a DEM of Antarctica with resolution of 500 meters using laser altimeter measurements from Ice, Cloud and land Elevation Satellite (ICESat) (DiMarzio et al, 2007). Yi et al (2005) calculated the slope of Greenland ice sheet by ICESat’s 8-day repeat orbit. Slope and aspect of Antarctic ice sheet with resolution of about 200 m are calculated using the 91-day repeat orbit data of ICESat. The surface elevation changes of the ice sheet are considered in our calculation. The level 2 Antarctic Ice Sheet Altimetry Data product (GLA12) are used to calculate slope and aspect in this study. ICESat ground tracks on Antarctic ice sheet after filtering and corrections 3. Slope and aspect can be determined by combining slopes in East-West direction and along-track direction
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