Solution and Analysis of Glacier-Scale Point-Mass Modeling for the West Antarctic Ice Sheet from 2002 to 2023

Using a two-step point-mass modeling method, a high-resolution (27 km × 27 km) point-mass product over the WAIS (West Antarctic Ice Sheet) at a glacier scale from April 2002 to December 2023 is derived. This method employs the Tongji-Grace2022 time-variable gravity field model derived from the GRACE (Gravity Recovery and Climate Experiment) and its successor GRACE-FO (GRACE Follow-On), and high-resolution constraint information from satellite altimetry are employed. Over the study period, the estimated mass change rate of the WAIS is -139.36 ± 19.92 Gt/a, contributing a global mean sea level rise of 0.38 ± 0.06 mm/a, which is consistent with the estimates from the global mascon (mass concentration) products of the three major GRACE official institutions but with significantly improved spatial resolution. Through regression fitting, we evaluated the products from the three major official institutions, satellite altimetry products, and our product using an independent product derived from input-output method. The results demonstrate that our product outperforms the others in estimating mass change rates for 20 glaciers (groups) in the WAIS. It has the smallest intercept, with coefficients of 0.82 for linear regression and an R² of 0.93, both significantly higher than those of the counterparts. Compared to satellite altimetry results, our product has a higher R² and a smaller intercept, indicating higher estimation accuracy. During the study period, the longterm surface mass anomaly and ice dynamics-related mass change rates of the WAIS are -11.70 ± 0.59 Gt/a and -113.58 ± 6.56 Gt/a, respectively, indicating that ice dynamics is the dominant factor of the overall mass loss. The combined long-term mass change rates of four major glaciers (or glacier groups)—Pine Island, Thwaites, Getz, and the PSKP (Pope, Smith, Kohler, and Philbin glaciers) glacier group—account for approximately 90% of the total mass change in the WAIS. Their individual rates are -44.19 ± 3.33, -26.17 ± 5.44, -27.04 ± 0.94, and -27.92 ± 1.02 Gt/a, respectively, with corresponding contributions to global mean sea level rise of 0.12 ± 0.01, 0.072 ± 0.015, 0.075 ± 0.003, and 0.077 ± 0.003 mm/a respectively.