Reconstructing Continuous Ice Sheet Elevation Changes in the Amundsen Sea Sector During 2003–2021 by Merging Envisat, ICESat, CryoSat‐2, and ICESat‐2 Multi‐Altimeter Observations.

The Amundsen Sea (AS) sector in West Antarctica accounts for a significant proportion of Earth's ice losses and is the largest contributor of Antarctica's mass loss. To evaluate its contribution to global sea‐level rise, we reconstruct the long‐term continuous surface elevation changes (CSEC) record of the AS sector by an improved least‐squares plane fitting method (ILSPFM), which merged the relative surface elevation change (SEC) series instead of height from Envisat, ICESat, CryoSat‐2, and ICESat‐2 missions during 2003–2021. The accuracy of CSEC is improved by 25.9% using ILSPFM. The average rate of CSEC in the AS sector was −24.25 ± 0.48 cm yr−1 during 2003–2021. The largest signals of SEC are found over Pine Island, Thwaites, and Pope Glaciers, with the largest decline of SEC over Pope Glacier with a total SEC of −82.44 ± 7.21 m and an annual change rate of −4.34 ± 0.38 m yr−1. The ridge between Pine Island and Thwaites Glaciers is found in the AS sector, indicating that the change of ice sheet is dynamic thinning and closely related to the topography and the distance from the grounding line. Compared with meteorological data sets, we find that the codirectional fluctuation in CSEC is delayed by 3 months with surface temperature, and the precipitation leading SEC series as the phase arrow points straight down from the cross wavelet transform. Our new record shows that the AS sector thinned rapidly from 2003 to 2021 but decelerated from 2019 to 2021, and it was clearly correlated to the surface temperature, precipitation, and local terrain. Plain Language Summary: With the intensification of global climate change, the melting of glaciers and ice shelves around the Amundsen Sea (AS) sector in Antarctica has caused a large amount of glacial meltwater to flow into the ocean, directly leading to the rapid rise of global sea levels. Therefore, it is of great scientific and practical significance to determine the high‐precision, high‐resolution, and long‐term continuous ice sheet surface elevation change (SEC) to predict future global sea‐level changes. Considering the different characteristics and abilities of different altimeter missions, we developed an improved least‐squares plane fitting method (ILSPFM) to merge radar and laser multi‐mission satellite altimetry. The ILSPFM is applied to reconstruct the 2003–2021 ice sheet continuous SEC (CSEC) record in the AS sector using Envisat, ICESat, ICESat‐2, and CryoSat‐2 observations, and it is compared to IceBridge and GRACE Mascon products. The root mean square errors of CSEC is improved by 25.9% compared with the simple combination of individual SEC series from Envisat/ICESat/CryoSat‐2/ICESat‐2. This study highlights the potential of the CSEC multi‐mission series determined by the ILSPFM as a reliable data set to support our understanding of the response mechanism of glaciers to climate change and for predicting global sea‐level changes. Key Points: An improved least‐squares plane fitting method is proposed to merge radar and laser multi‐altimeter data in the Amundsen Sea (AS) sectorContinuous surface elevation change data set (2003–2021) in AS sector is reconstructed with the average rate −24.25 ± 0.48 cm/yrOur new record shows that the AS sector thinned rapidly from 2003 to 2021 but decelerated from 2019 to 2021 [ABSTRACT FROM AUTHOR]

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