Abstract
Abstract. This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new Ice, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related mass change estimates for the entire Antarctic ice sheet ranged from 53 to 103 Gt yr−1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr−1. Over the time frame February 2003–October 2009, the corresponding ice mass change showed an average value of −100 ± 44 Gt yr−1 (EA: 5 ± 38, WA: −105 ± 22), consistent with other recent estimates in the literature, with regional mass loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and ice mass change, particularly with respect to determining more reliable uncertainties.
Highlights
IntroductionThe effects of glacial-isostatic adjustment (GIA) are typically removed in the data processing using modeled values; the uncertainty in current GIA models is on the order of tens of Gt yr−1, or on the same scale as the estimated ice mass change (Gunter et al, 2009; Horwath and Dietrich, 2009; King et al, 2012; Velicogna and Wahr, 2013)
Over the past decade, there has been general consensus within the glaciological and geodesy communities that the ice sheet of Antarctica is currently experiencing a significant loss in ice mass on the order of tens to hundreds of gigatons (1 Gt = 1012 kg) per year (Chen et al, 2006; Rignot et al, 2008; Horwath and Dietrich, 2009; Jacob et al, 2012; Shepherd et al, 2012)
This study revisited the approach developed by Riva et al (2009) for estimating present-day glacial-isostatic adjustment (GIA) and ice mass change using a combination of satellite altimetry and gravimetry
Summary
The effects of GIA are typically removed in the data processing using modeled values; the uncertainty in current GIA models is on the order of tens of Gt yr−1, or on the same scale as the estimated ice mass change (Gunter et al, 2009; Horwath and Dietrich, 2009; King et al, 2012; Velicogna and Wahr, 2013) This is due to the very sparse (in both space and historical time) geophysical and climatological data available for Antarctica, which are required to constrain historical changes in ice history and GIA models. This uncertainty in the GRACE estimates makes the monitoring and prediction of current mass loss trends much less reliable and highlights the need to make improvements in the determination of the GIA and ice-mass change signals
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