A Comparison of Observed Antarctic Uplift Rates with Postglacial Rebound Model Predictions
Abstract
Postglacial rebound (PGR) or glacial isostatic adjustment (GIA) models for Antarctica have been proposed and revised for many years but only recently has GPS crustal uplift data been available to compare to model predictions. Bevis et al. (2009) described new observations of crustal uplift in Antarctica and compared the results to GIA model predictions, including the IJ05 model of Ivins and James (2005). IJ05 published predicted uplift rates based on a small number of different Earth models but many other possible Earth model (viscosity) combinations could be examined. Here we systematically vary the viscosity in the asthenosphere, transition zone and lower mantle and determine which IJ05 Earth models agree best with the Bevis et al. observations using a χ2 measure of goodness-of-fit. Predictions were generated for mantle viscosities ranging from 1x1016Pa s to 1x1022Pa s for the asthenosphere, 1x1016Pa s to 2x1023Pa s for the transition zone, and 1x1019Pa s to 1x1026Pa s for the lower mantle. The IJ05 predictions that agree best with the Bevis et al. observations have a χ2 per degree of freedom of 16. This is a better fit than the null hypothesis which gives a χ2 of 44 but the departure from a value of one for the best-fit model indicates the need for model revisions and/or that uncertainties are too optimistic. Additionally, the mantle viscosities of the best-fit models are much higher than expected for Antarctica. The smallest χ2 values are found for an asthenospheric viscosity of 5x1020Pa s, transition zone viscosity of 1x1023Pa s and lower mantle viscosity of 2x1023Pa s whereas the expected viscosity of the asthenosphere beneath West Antarctica is probably less than 1020Pa s. At the regional level, some areas show good agreement with the observations while other areas, such as the Antarctic Peninsula, do not agree well with the observations for any choice of mantle viscosity. For some parts of the Antarctic Peninsula, it is possible that tectonic effects are present in the observations and contribute to the mismatch between observations and predictions. Another factor to be investigated is the influence of possible biases in the reference frame realization of the GPS velocities.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C21C0563D
- Keywords:
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- 0776 CRYOSPHERE / Glaciology;
- 0798 CRYOSPHERE / Modeling;
- 1621 GLOBAL CHANGE / Cryospheric change