Gravity inversion for sub-ice shelf bathymetry; best practises, uncertainty estimates, and open-source software

Sub-ice-shelf bathymetry exerts a primary control on the stability of ice shelves by guiding melt-inducing water masses and through pinning points that resist the flow of the overriding ice. Collecting sub-ice-shelf bathymetry data using active source seismic surveying or direct observations is inefficient, and often impractical. Gravity methods provide a pragmatic alternative, by which observed variations in Earth’s gravitational field are used to estimate the underlying bathymetry. We utilize a new open-source gravity inversion algorithm (Invert4Geom) developed specifically for modeling sub-ice-shelf bathymetry and estimating the spatially variable uncertainty in the results. Here we test the inversion on a suite of models created with real bathymetric data from Antarctica's Ross Sea. These tests enable 1) determination of the best practices for conducting bathymetric inversions, 2) recognition of the limitations of the inversion and uncertainty quantification, and 3) identification of where community efforts should be focused for the future of determination of Antarctica’s sub-ice-shelf bathymetry. We find that estimating and removing the regional component of gravity prior to the inversion is the largest source of error in the resulting bathymetry model, but this error can be greatly reduced with additional bathymetry constraints. Additionally, we explore the effectiveness of inversions with varying levels of data noise, spacing, and strengths of the regional gravity field.