Comparison of observations and modelling of surface mass balance variations in East Antarctica

Abstract

Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and the contribution to changes in global sea level that is makes. In recent years, the Antarctic ice sheet has experienced increased temperatures inducing surface melting, accelerated ice flow and ice discharge but also an increase in accumulation. Geodetic observations suggest variable behaviour across the ice sheet, with an increase in mass over a vast area of East Antarctica and substantial thinning in West Antarctica.

Despite considerable improvement on surface mass balance estimates using a variety of techniques, disparity remains mainly due to uncertainties of each method and the unknown contribution of glacial isostatic adjustment, the response of the lithosphere to prolonged surface loads. Estimates of bedrock uplift rates are limited and existing models are poorly constrained due to the lack of observations as a result of the extensive permanent ice coverage in Antarctica.

This study investigates the possibility of combining and comparing altimetry and gravity observations by employing a regional climate model to simulate near surface climate and firn compaction, to separate the contributing ice sheet mass balance components of surface mass, firn compaction, ice dynamics and glacial isostatic adjustment within the observed signals. The region of interest covers an area including Enderby, Kemp and Mac.Robertson Land, in East Antarctica, an area where an increase in ice mass and ice height has been recorded over the past decade. Despite the general agreement that the positive signal is primarily related to increased snowfall, large uncertainties remain in bedrock uplift rates in this region due to the lack of observations. Estimates of ice dynamic rates are obtained by removing modelled surface elevation variations, due to surface mass and firn compaction, from altimetry observations, which are subsequently employed in models of mass variations to compare with gravimetric observations.