Synthetic bed topographies for Antarctica and their utility in ice sheet modelling.

Bed topography is a key control on the evolution of the Antarctic Ice Sheet, influencing ice flow, grounding line retreat and the rate and timing of ice mass loss. To assess the sensitivity of ice sheet evolution to bed variability in ice sheet models, synthetic gridded bed topography datasets are often used. Here, we review methods commonly used to generate synthetic beds, their associated uncertainties and the influence of the approach on the characteristics of the resulting bed. Using the Aurora Subglacial Basin in East Antarctica as a case study, we evaluate the impact of five synthetic bed generation methods on projected ice mass loss under a high emission scenario. Sea-level rise estimates vary by up to 11% (SSP5-8.5 forcing scenario) and 32% (RCP2.6) at 2300 CE when basal friction coefficients from the friction law are optimized for each bed, and by up to 23% (SSP5-8.5) and 51% (RCP2.6) at 2300 CE when using non-optimized coefficients. Our results highlight the importance of relatively small bed variations on the timing and extent of grounding line retreat and the need for process-informed representation of the basal friction in decadal- to centennial-scale sea-level projections. This article is part of the Theo Murphy meeting issue 'Next generation ice-sheet bed measurements'.