Spatially heterogeneous nonlinear signal in Antarctic ice-sheet mass loss revealed by GRACE and GPS

Nonlinear trends (i.e. quadratic trends, usually defined as accelerations) in Antarctic ice mass loss due primarily to the complex climate warming forcing regimes have induced large uncertainty to future sea level projection. Here, we quantify the nonlinear and spatially varying mass losses in the Antarctic ice sheet during the last two decades using the satellite gravimetry data collected by Gravity Recovery And Climate Experiment (GRACE) and its successor GRACE Follow-On. We use a regional inversion methodology to generate the mass change time-series over Antarctica. Our findings reveal that seven regions have evidenced significant nonlinear mass change. These regions are all concentrated along the coast of Antarctica and show spatially heterogeneous mass balance nonlinear trend patterns. Among them, the Amundsen Sea Embayment (ASE) and the Dronning Maud Land (DML) are found to be particularly sensitive to short-term climate variability. The GRACE-inferred nonlinear mass balance signal can be confirmed by independent Global Positioning System (GPS) observations, and the difference between the nonlinear vertical deformation trends estimated by GRACE and GPS, especially in ASE, is likely due to the imperfect correction of the glacial isostatic adjustment (GIA) effect. For Antarctic ice sheet as a whole, GRACE satellite gravimetry indicates an ice mass loss of -101.3 +/- 18.0 Gt yr(-1), with an accelerated loss of -6.4 +/- 1.3 Gt yr(-2) during 2002-2021.

Automated summary

By analyzing the satellite gravimetry data from GRACE and GRACE Follow-On, this study quantifies the nonlinear and spatially varying mass losses in the Antarctic ice sheet over the past two decades. The research reveals significant nonlinear mass change in seven regions along the coast of Antarctica, with diverse spatial patterns. The overall ice mass loss of the Antarctic ice sheet is estimated to be -101.3 +/- 18.0 Gt yr(-1), accelerating at a rate of -6.4 +/- 1.3 Gt yr(-2) from 2002 to 2021.