Antarctic ice mass balance is determined by precipitation and ice discharge, and understanding their relative contributions to contemporary Antarctic ice mass change is important to project future ice mass loss and resulting sea level rise. There has been evidence that anomalous precipitation affects Antarctic ice mass loss estimates, and thus the precipitation contribution should be understood and considered in future projections. In this study, we revisit changes in Antarctic ice mass over recent decades and examine precipitation contributions over this period. We show that accumulated (time-integrated) precipitation explains most inter-annual anomalies of Antarctic ice mass change during the GRACE period (2003–2017). From 1979 to 2017, accumulated Antarctic precipitation contributes to significant ice mass loss acceleration in the Pacific sector and deceleration in the Atlantic-Indian Sectors, forming a bi-polar spatial pattern. Principal component analysis reveals that such a bi-polar pattern is likely modulated by the Southern Annular Mode (SAM). We also find that recent ice mass loss acceleration in 2007 is related to a variation in precipitation accumulation. Overall ice discharge has accelerated at a steady rate since 1992, but has not seen a recent abrupt increase.

Accurate estimation of ongoing Antarctic ice mass change is important to predict future ice mass loss and subsequent sea level rise. Over the past two decades, Antarctic ice mass changes have been observed by the gravity recovery and climate experiment (GRACE) gravity mission, but the low spatial resolution of GRACE has limited understanding of glacial‐scale contributions. In this study, we combine GRACE and altimetry data to obtain mass change estimates with greatly improved spatial resolution. Combined estimates are obtained by a constrained linear deconvolution algorithm used in a previous GRACE study. Satellite altimetry observations are introduced as an a priori and resulting estimates retain the high spatial resolution of satellite altimetry, but when smoothed agree with low resolution GRACE data. These glacial‐scale estimates also agree with ice budget calculations using the input‐output method.

<p>We partitioned Antarctic ice mass changes (2003-2020) into the contributions of surface mass balance (SMB) and ice discharge over 27 drainage basins, based on the combined estimates of satellite gravimetry and altimetry observations and a numerical SMB model. Our analysis indicates that the ice discharge has played a dominating role in ongoing ice mass losses and accelerations, especially in the glaciers near Amundsen and Bellingshausen Sea in West Antarctica. In particular, the mass losses in the Thwaites and Pine Island Glaciers have been mostly controlled by ice discharge, while the contribution of SMB has been minor. On the other hand, SMB contributed large portions of ice mass imbalance in East Antarctica, such as glaciers near the Dronning Maud Land and Wilkes Land. An inaccurate GIA model is a potential source of uncertainty in our estimates.</p>

The strong El Niño has delayed the ice mass loss of West Antarctica under global warming by inducing weakening of the Amundsen Sea Low (ASL) and consequent extreme snowfall. However, it is not yet clear whether the mechanism will continue in the future warmer climate. Analysis of future climate scenarios from the CMIP6 models shows that the El Niño-induced increases in snowfall over West Antarctica will disappear with intensifying global warming. In the high-emissions scenario (SSP5-8.5), precipitation anomaly owing to El Niño turns to negative from the 2050s, and from the 2060s in the SSP3-7.0, and consequently the El Niño-induced mass loss delay effect vanishes. This is because the stronger polar jet related with positive SAM trend would shift the ASL anomaly toward the east and the equator in the warmer climate, which would prevent water vapor transport into the interior of West Antarctica.

<p>West Antarctica has been losing their ice mass due to global warming, and the El Niño has delayed the ice mass loss by inducing weakening of the Amundsen Sea Low (ASL), encouraging of poleward moisture flux and consequent extreme precipitation. However, it is not yet revealed whether the delay effect will continue in the future. We analyzed future scenarios from the CMIP6 Earth system models (ESMs) to identify future change and identified that the El Niño-driven mass increase by precipitation will vanish in the high-emission future scenarios. Precipitation anomaly in response to El Niño starts to be negative from the 2050s in the SSP5-8.5 and from the 2060s in the SSP3-7.0, which means that the El Niño-driven delay effect disappears. It is because the moisture transport into West Antarctica is prevented due to east-equatorward migration of El Niño-induced ASL anomaly as global warming intensifies. The strengthened polar jet associated with positive Southern Annular Mode (SAM) trend moves the ASL anomaly east- and equatorward under global warming.</p>