GOCE's view below the ice of Antarctica: Satellite gravimetry confirms improvements in Bedmap2 bedrock knowledge

Abstract

Accurate knowledge of Antarctica's topography, bedrock, and ice sheet thickness is pivotal for climate change and geoscience research. Building on recent significant progress made in satellite gravity mapping with European Space Agency's Gravity field and Ocean Circulation Explorer (GOCE) mission, we here reverse the widely used approach of validating satellite gravity with topography and instead utilize the new GOCE gravity maps for novel evaluation of Bedmap1/2. Space-collected GOCE gravity reveals clear improvements in the Bedmap2 ice and bedrock data over Bedmap1 via forward modeled topographic mass and gravity effects at spatial scales of 400 to 80 km. Our study demonstrates GOCE's sensitivity for the subsurface mass distribution in the lithosphere and delivers independent evidence for Bedmap2's improved quality, reflecting new radar-derived ice thickness data. GOCE and Bedmap2 are combined to produce improved Bouguer gravity maps over Antarctica. We recommend incorporation of Bedmap2 in future high-resolution global topography and geopotential models and its use for detailed geoid modeling over Antarctica.

Estimates ofTefor continental regions using GOCE gravity

“…An additional problem in Antarctica is the ice cover, which conceals the bedrock topography that gives rise to the relevant gravity anomalies. Fortunately there are now sufficient radar measurements of ice thickness to provide a reasonably accurate map of basement topography (Fretwell et al 2013), which Hirt (2014) has shown correlates with the GOCE gravity field.…”

Earth2014: 1 arc-min shape, topography, bedrock and ice-sheet models – Available as gridded data and degree-10,800 spherical harmonics

“…The Bedmap2 grids substantially improve over earlier Bedmap1 data compilations over Antarctica, as is evident e.g., from independent comparisons against gravimetry (Hirt 2014). Differences in bedrock elevations between Bedmap2 and Bedmap1 are at the level of several 100 m (up to 1-2 km maximum), where new ice thickness data has become available (Fretwell et al 2013, Fig 13 ibid).…”

Improving GOCE cross-track gravity gradients

“…GOCE gravity gradients are used as input for many stateof-the-art gravity field models Hashemi Farahani et al 2013;Schall et al 2014;Brockmann et al 2014;, contributing significantly to those models' high accuracy and spatial resolution, with downstream applications in oceanography, geophysics and geodesy (Knudsen et al 2011;Gruber et al 2012;Fuchs et al 2013;Becker et al 2014;Hirt 2014). Beyond that, the direct use of gravity gradients in geophysical applications is currently evolving (Van der Meijde et al 2015;Bouman et al 2016).…”