Elevation Changes of the Antarctic Ice Sheet from Joint Envisat and CryoSat-2 Radar Altimetry

Baojun Zhang,Quanming Yang,Jingbin Liu,Fei Li,Jiachun An,Tingting Liu,Zemin Wang,Hong Geng

doi:10.3390/rs12223746

Abstract

The elevation changes of ice sheets have been recognized as an essential climate variable. Long-term time series of these changes are an important parameter to understand climate change, and the longest time-series of ice sheet elevation changes can be derived from combining multiple Ku-band satellite altimetry missions. However, unresolved intermission biases obscure the record. Here, we revise the mathematical model commonly used in the literature to simultaneously correct for intermission bias and ascending–descending bias to ensure the self-consistency and cohesion of the elevation time series across missions. This updated approach is applied to combine Envisat and CryoSat-2 radar altimetry in the period of 2002–2019. We tested this approach by validating it against airborne and satellite laser altimetry. Combining the detailed temporal and spatial evolution of elevation changes with firn densification-modeled volume changes due to surface processes, we found that the Amundsen Sea sector accounts for most of the total volume loss of the Antarctic Ice Sheet (AIS), mainly from ice dynamics. However, surface processes dominate the volume changes in the key regions, such as the Totten Glacier sector, Dronning Maud Land, Princess Elizabeth Land, and the Bellingshausen Sea sector. Overall, accelerated volume loss in the West Antarctic continues to outpace the gains observed in the East Antarctic. The total volume change during 2002–2019 for the AIS was −68.7 ± 8.1 km3/y, with an acceleration of −5.5 ± 0.9 km3/y2.

Highlights

The elevation changes of ice sheets are the result of changes in ice sheet ice dynamics and weather-driven changes on the surface
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The accelerated ice volume loss in the coastal regions of West Antarctic Ice Sheet (WAIS) continues to outpace the gains made in the EAIS

Summary

Introduction

The elevation changes of ice sheets are the result of changes in ice sheet ice dynamics and weather-driven changes on the surface. Accounting for the intermission bias caused by differences in the position of the centers of gravity of the two satellites and the phase of the antennae and bias caused by orbital errors, is primary important problem for cross-calibrating observations from multiple altimeter missions [12]. This intermission bias was regarded as a constant and was corrected by calculating the global average in the open sea through the intersection [13]. We present an updated plane-fitting least-squares regression model for obtaining a long-term elevation time series of the Antarctic Ice Sheet (AIS) by combining radar altimetry missions.

Envisat and CryoSat-2 Altimetry Data

The Updated Least-Squares Regression Model

Calculation of the Combined Elevation Time Series

The Total Intermission Biases and the Intramission A–D Bias

Volume Time Series for the AIS

Conclusions