Complex Patterns of Antarctic Ice Sheet Mass Change Resolved by Time-Dependent Rate Modeling of GRACE and GRACE Follow-On Observations

The Antarctic Ice Sheet (AIS) is a major contributor to current global sea-level change and the largest potential source of future sea-level change. Variability in AIS mass balance on a wide range of spatiotemporal scales obscures secular trends, increasing the uncertainty of projections. We introduce a novel approach for analyzing satellite gravity observations to estimate time-varying mass-change rates and resolve the time scales and amplitudes of rate fluctuations. The new analysis resolves a higher degree of variability than expected over all AIS sectors. Quantifying rate fluctuations on a range of time scales, we demonstrate that loss from the West AIS is characterized by a multidecadal trend, whereas variations of the East AIS are dominated by substantial, short-term accumulation changes that impact AIS mass balance as whole. These complex spatiotemporal variabilities highlight the need to include stochastic processes in estimates of loss rates. Plain Language Summary Characterizing ice loss from the Antarctic Ice Sheet (AIS) as a constant rate, as is typically done, ignores significant temporal variability and leads to large uncertainties in the projection of future changes. We introduce a new approach that models the AIS mass- change rate as a time-dependent parameter, resulting in unexpectedly high variability in rates of mass loss from all sectors. We also quantify the amplitudes for the rate fluctuations for various time scales, identifying the roles of different AIS sectors in determining total mass imbalance over time. We conclude that observations and projections of AIS mass change must account for stochastic rate processes.

Automated summary

The Antarctic Ice Sheet (AIS) is a major contributor to global sea-level change, and its mass balance variability on different scales highlights the need to include stochastic processes in loss rate estimates. Loss from the West AIS shows a multidecadal trend, while variations in the East AIS are dominated by short-term accumulation changes. The analysis shows unexpected high variability in mass-loss rates from all sectors, emphasizing the importance of considering time-dependent parameters in projecting future ice sheet changes.