Evaluation of Slope Correction Methods to Improve Surface Elevation Change Estimation over Antarctic Ice Sheet using SARAL/AltiKa

Abstract

Antarctic Ice Sheet (AIS) surface elevation change plays a crucial role in understanding the ice sheet mass balance. The present study focuses on improving AIS surface elevation estimations by incorporating slope correction methods called Direct Method (DM) using SARAL/AltiKa 40 Hz geophysical data record for 2013 (Exact Repeat Mission) and 2020 (Drifting Phase) with terrain slope ranges from 0° to 0.85°. The NASA's Ice, Cloud, and land Elevation Satellite (ICESat) Digital Elevation Model (DEM) has been utilized as a priori topography model to retrieve slope of the AIS terrain. While comparing the two direct methods (DM1 & DM2) based slope corrected elevations with Operation Ice Bridge (OIB) elevation data of November 2013, the RMSE resulted in 0.35 and 0.37 m and biases of the order of 0.26 m and 0.28 m for DM1 and DM2 respectively. Moreover, comparison with ICESat DEM showed the RMSE of the order of 1.81 and 2.09 m, and biases of the order of 0.95 and 0.99 m for DM1 and DM2, respectively. It has been observed that DM1 is the most suitable method for correcting terrain slope with the lowest RMSE and bias. Moreover, the slope induced error correction methods show utmost importance in estimating accurate elevation, especially over undulating terrain of AIS.