An assessment of forward and inverse GIA solutions for Antarctica.

Alba Martín‐Español,Stuart B Andrews,Matt A King,Philip Moore,Jonathan L Bamber,Andrew Zammit‐Mangion

doi:10.1002/2016jb013154

Abstract

In this work we assess the most recent estimates of glacial isostatic adjustment (GIA) for Antarctica, including those from both forward and inverse methods. The assessment is based on a comparison of the estimated uplift rates with a set of elastic‐corrected GPS vertical velocities. These have been observed from an extensive GPS network and computed using data over the period 2009–2014. We find systematic underestimations of the observed uplift rates in both inverse and forward methods over specific regions of Antarctica characterized by low mantle viscosities and thin lithosphere, such as the northern Antarctic Peninsula and the Amundsen Sea Embayment, where its recent ice discharge history is likely to be playing a role in current GIA. Uplift estimates for regions where many GIA models have traditionally placed their uplift maxima, such as the margins of Filchner‐Ronne and Ross ice shelves, are found to be overestimated. GIA estimates show large variability over the interior of East Antarctica which results in increased uncertainties on the ice‐sheet mass balance derived from gravimetry methods.

Highlights

Estimating the mass balance of the ice sheets and their current contribution to sea-level rise is a challenging research task in Earth Sciences
Uplift rates over the Amundsen Sea Embayment (ASE) sector and over the North Antarctic Peninsula (NAP) are underestimated by all available glacial isostatic adjustment (GIA) solutions
Thinner lithosphere and lower viscosity Earth structure correlates with more rapid and shorter length-scale uplifts, and we suggest that these regions both are underlain by low viscosity mantle, in agreement with the findings of Nield et al [2014] for the NAP and the suggestion of Groh et al [2012] for the ASE

Summary

Introduction

The Gravity Recovery and Climate Experiment (GRACE) observes temporal gravity variations from which surface mass changes over a given region can be deduced. In order to estimate the mass balance of ice sheets from gravimetry methods, the contribution from GIA must be accounted for. GIA results in what is commonly considered to be a secular change (over timescales of centuries) in surface deformation and gravity field. It is normally accounted for using forward models which combine deglaciation history models and viscoelastic Earth structure models [e.g., Sasgen et al, 2007; Velicogna and Wahr, 2006]. The GRACE-deduced mass change associated with climate and hydrology changes is strongly dependent on the GIA model used

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