Antarcticaʼs hypsometry and crustal thickness: Implications for the origin of anomalous topography in East Antarctica

Abstract

The hypsometry of Antarctica revealed by BEDMAP2 data is characterised by deglaciated modal elevations of ∼−450 m and ∼650 m for West and East Antarctica, respectively, and an East Antarctic plateau that is topographically anomalous by ∼400–600 m with respect to global continental modal elevation estimates. Superimposed on the East Antarctic plateau are the Gamburtsev Subglacial Mountains, the Dronning Maud Land Mountains and the Vostok Highlands with modal elevations ∼400 m in excess of the East Antarctic mode. To ascertain whether East Antarcticaʼs anomalous topography can be attributed to Airy-type crustal compensation, a continental-scale crustal thickness model was derived from the inversion of GOCO03S satellite gravity data constrained by seismic crustal thickness estimates. The average crustal thickness of East Antarctica is ∼40 km (for West Antarctica ∼24 km), a value typical of continental shields, and while crustal thicknesses of >50 km locally beneath the Gamburtsev Subglacial Mountains and Dronning Maud Land can account for their differential modal elevation above the plateau, crustal thicknesses elsewhere across East Antarctica offer no suggestion of crustal-level continental-scale support for the broader plateau. Enderby Land, for example, resides on the plateau and is characterised by a modal elevation of ∼750 m and crust ∼40 km thick, whereas off the plateau in East Antarctica, the Aurora and Wilkes Subglacial Basins have modal elevations of ∼−50 m and ∼50 m, respectively, yet similarly thick crust. The lack of crustal support for the elevated broader East Antarctic plateau, coupled with seismic images showing fast upper mantle velocities beneath the plateau, suggest a mid-to-lower mantle source for East Antarcticaʼs anomalous topography.