Gravity Topography Modeling of the Denman Glacier Region Using a Geostatistical Approach

Abstract. The Denman Glacier is one of East Antarctica’s most dynamic outlet systems and is modeled to host the deepest continental marine trough, with the potential to contribute up to ∼ 1.5 m of global sea level rise. Yet its bed geometry remains poorly constrained because airborne radar surveys struggle to image steep, narrow, and deeply incised troughs, and existing continental-scale compilations rely heavily on interpolation or mass-conservation assumptions. During the Australian Denman Terrestrial Campaign 2023/24, high-resolution ground-based gravity measurements were collected across the deepest part of the trough, providing short-wavelength constraints that complement ICECAP airborne gravity and radar data.

We use a two-scale, ensemble-based gravity inversion to reconstruct Denman’s bed topography. A geostatistical separation of terrain and non-terrain gravity effects generates multiple plausible regional background fields, and each is explored with a random-walk Metropolis–Hastings Markov Chain Monte Carlo (MCMC) inversion in which small, spatially correlated Gaussian perturbations modify the bed. Within each realization, candidate geometries are jointly evaluated against the gravity signal and radar picks, with gravity providing the dominant constraint in regions lacking radar coverage.

The resulting ensemble reveals a more rugged, spatially variable, and internally segmented subglacial landscape than represented in current bed products. Along cross-trough profiles, the best-fit gravity-derived bed generally falls between BedMachine and Bedmap3 yet exhibits steeper trough walls and greater lateral relief. Depth-to-magnetic-source estimates further support contrasting lithologies across the trough, with crystalline basement to the west and weaker, sedimentary signatures to the east.

The inferred geometry, characterized by steep flanks and an inland-sloping basin, reinforces the susceptibility of Denman Glacier to Marine Ice Sheet Instability. These results highlight the importance of incorporating geophysical inversion methods into future Antarctic bed-mapping efforts and provide an ensemble of bed realizations suitable for ice flow modeling and assessments of grounding line stability.