Time dependent contributions to the mass balance of Antarctic drainage systems from satellite geodesy and model products

We use satellite gravimetry (GRACE) and satellite altimetry observations to study time-dependent contributions from ice-dynamics and climatological forcing to mass changes of the Antarctic drainage basins. Products from regional climate modelling and firn modelling allow the separation of contributing signals to the mass balance. Linear trends over discrete time periods are a common method to investigate the mass balance of drainage systems. To overcome limitations of those deterministic approaches, we apply a coupled state space model to time series of Antarctic drainage systems from April 2002 to August 2016. We evaluate time series from GRACE, multi-mission altimetry, modelled surface mass balance (SMB), and modelled firn thickness change. The state space model enables the separation of long-term and short-term changes. We parametrize long-term variations by a trend with a time-variable rate which we assume is present in GRACE and altimetry observations. Further we allow for cyclic, auto-correlated, or uncorrelated residual short-term variations. Benefits of this approach are: (1) We can avoid restrictions due to predefined time-periods, (2) we do not enforce a single density to relate mass and volume changes, and (3) we allow for unmodeled SMB and firn thickness changes which are absorbed in the state space filtering framework. Our results confirm the accelerating ice-dynamic contribution in West Antarctica and low temporal variability of the long-term signal in East Antarctica.