A new glacial isostatic adjustment model for Antarctica: calibrated and tested using observations of relative sea-level change and present-day uplift rates

Abstract

SUMMARY We present a glacial isostatic adjustment (GIA) model for Antarctica. This is driven by a new deglaciation history that has been developed using a numerical ice‐sheet model, and is constrained to fit observations of past ice extent. We test the sensitivity of the GIA model to uncertainties in the deglaciation history, and seek earth model parameters that minimize the misfit of model predictions to relative sea‐level observations from Antarctica. We find that the relative sea‐level predictions are fairly insensitive to changes in lithospheric thickness and lower mantle viscosity, but show high sensitivity to changes in upper mantle viscosity and constrain this value (95 per cent confidence) to lie in the range 0.8–2.0 × 1021 Pa s. Significant misfits at several sites may be due to errors in the deglaciation history, or unmodelled effects of lateral variations in Earth structure. When we compare our GIA model predictions with elastic‐corrected GPS uplift rates we find that the predicted rates are biased high (weighted mean bias = 1.8 mm yr–1) and there is a weighted root‐mean‐square (WRMS) error of 2.9 mm yr–1. In particular, our model systematically over‐predicts uplift rates in the Antarctica Peninsula, and we attempt to address this by adjusting the Late Holocene loading history in this region, within the bounds of uncertainty of the deglaciation model. Using this adjusted model the weighted mean bias improves from 1.8 to 1.2 mm yr–1, and the WRMS error is reduced to 2.3 mm yr–1, compared with 4.9 mm yr–1 for ICE‐5G v1.2 and 5.0 mm yr–1 for IJ05. Finally, we place spatially variable error bars on our GIA uplift rate predictions, taking into account uncertainties in both the deglaciation history and modelled Earth viscosity structure. This work provides a new GIA correction for the GRACE data in Antarctica, thus permitting more accurate constraints to be placed on current ice‐mass change.

Simultaneous solution for mass trends on the West Antarctic Ice Sheet

“…Figure 6b shows the standard deviation of our GIA estimate and it is evident that, where robust GPS data exist, the errors are substantially reduced locally. Comparing our results, basin by basin, with other recent GIA estimates including two forward models (W12a, Whitehouse et al, 2012, andIJ05-R2 Ivins et al, 2013) and two data-driven solutions (Gunter et al, 2014, andAGE-1 Sasgen et al, 2013) we find that we have, in general, best agreement with AGE-1. Basin definitions are shown in Fig.…”

Glacial retreat in the Amundsen Sea sector, West Antarctica – first cosmogenic evidence from central Pine Island Bay and the Kohler Range

“…Whitehouse et al, 2012aWhitehouse et al, , 2012b. The former is consistent with the suggestion that the Pine Island ice front had reached its modern-day position by the early Holocene , and references therein).…”

A fully coupled 3-D ice-sheet–sea-level model: algorithm and applications

“…Maris et al, 2014). In a future study we will investigate the parameter space for both the Earth and ice-sheet models, and we will compare with observational data (see for example Whitehouse et al, 2012b;Briggs et al, 2013) on a global scale (Tushingham and Peltier, 1992).…”

“…Whitehouse et al, 2012b), RSL over the glacial cycle (e.g. Deschamps et al, 2012;Grant et al, 2012;Austermann et al, 2013) and ice extent (e.g.…”