Changes in Antarctic Ice Sheet Surface Elevation from a Quarter-century of Combined Radar and Laser Altimetry

Satellite altimetry provides the longest continuous record of elevation change for assessing the mass balance of the Antarctic Ice Sheet, providing a unique opportunity to observe the ice sheet's response to changes in atmosphere and ocean over the last few decades. The accuracy of altimetry-measured elevation change, from which this mass balance is derived, is of
vital importance for quantifying Antarctica's contribution to sea-level rise, and for understanding the physical processes governing changes of the ice sheet. Studies have shown that the rate of Antarctica's mass loss has accelerated over the last decade, largely a result of accelerated ice flow from the Amundsen Sea sector of West Antarctica. Not all areas of the ice sheet are thinning however. Increases in precipitation have resulted in rapid thickening over parts of East Antarctica, especially in Dronning Maud Land. A key question is how these relatively recent changes contrast against the observed longer-term trend and variability. Observations from overlapping satellite altimeter mission over the last three decades can help to answer
this question. Here, we have developed a novel framework for cross-calibrating and synthesizing multimission altimetry records, with a further emphasis on generating state-of-the-art corrections for issues affecting the altimeter measurement (such as surface slope and variations in surface scattering) in order to increase the reliability and accuracy of the full altimetry
record. The framework allows us to construct consistent time series at fine spatial and temporal scales for the majority of the ice sheet, with a corresponding assessment of the overall uncertainty of the solutions. We present results detailing the complex long-term pattern of elevation change, observed by the altimeters, and discuss the current improvement and imitations of the altimeter record. This effort will allow us to improve upon existing records of the long-term evolution of the Antarctic Ice Sheet, providing an invaluable dataset for
advancing ice sheet modeling efforts and for disentangling the causal mechanisms responsible for ice sheet mass change.