23 Aug 2023
 | 23 Aug 2023
Status: this preprint is currently under review for the journal TC.

Globally consistent estimates of high-resolution Antarctic ice mass balance and spatially-resolved glacial isostatic adjustment

Matthias O. Willen, Martin Horwath, Eric Buchta, Veit Helm, Bernd Uebbing, and Jürgen Kusche

Abstract. A detailed understanding of how the Antarctic Ice Sheet (AIS) responds to a warming climate is needed because it will most likely increase the rate of global mean sea level rise. Time-variable satellite gravimetry, realized by the GRACE and GRACE-FO missions, is directly sensitive to AIS mass changes. However, gravimetric mass balances are subject to two major limitations: First, the usual correction of the glacial isostatic adjustment (GIA) effect by modelling results is a dominant source of uncertainty. Second, satellite gravimetry allows for a resolution of a few hundred kilometres only, which is insufficient to thoroughly explore causes of AIS imbalance. We have overcome both limitations by the first global inversion of data from GRACE/GRACE-FO, satellite altimetry (CryoSat-2), regional climate modelling (RACMO2), and firn densification modelling (IMAU-FDM). The inversion spatially resolves GIA in Antarctica independently from GIA modelling jointly with changes of ice mass and firn air content at 50 km resolution. We find an AIS mass balance of -144 ± 27 Gt a-1 from Jan 2011 to Dec 2020. This estimate is the same, within uncertainties, as the statistical analysis of 23 different mass balances evaluated in IMBIE. The co-estimated GIA corresponds to an integrated mass effect of 86 ± 21 Gt a-1 over Antarctica and it fits better with GNSS results than other GIA predictions. From propagating covariances to integrals, we find a correlation coefficient of -0.97 between the AIS mass balance and the GIA estimate. Sensitivity tests with alternative input data sets lead to results within assessed uncertainties.

Matthias O. Willen et al.

Status: open (until 20 Oct 2023)

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Matthias O. Willen et al.

Matthias O. Willen et al.


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Short summary
Shrinkage of the Antarctic Ice Sheet (AIS) leads to sea level rise. Satellite gravimetry measures AIS mass changes. We have applied a new method that overcomes two limitations: low spatial resolution and large uncertainties due to Earth interior mass changes. To do so, we additionally include data from satellite altimetry and climate modelling. Advantages are that the data is evaluated globally with thoroughly characterized errors. The results are in better agreement with independent data.