Under what conditions will the Wilkes Subglacial Basin exhibit large scale retreat?

The Wilkes Subglacial Basin (WSB) holds approximately 3-4 m sea-level equivalent ice volume (Rignot et al., 2019; Crotti et al., 2022), and is characterised by a reverse-sloping bed, making it vulnerable to marine ice sheet instability. However, the conditions and indeed the possibility of large retreat is still highly debated. Using the finite element ice-sheet model, Úa, we conduct a sensitivity analysis to determine the climate conditions for large scale retreat. We further explored uncertainties arising from poorly known physical mechanisms, particularly the sliding law.

 

Our simulations are initialised using present-day ice dynamics reproduced through inversion methods. Transient simulations of 500 years are then conducted with different surface temperature forcing. In the control experiment, constant present-day thermal forcing is applied to the local quadratic parameterisation (Jourdain et al., 2020) for sub-ice-shelf melting, and surface mass balance is prescribed using constant RACMO model output (Noël et al., 2023). Increase of surface temperature proportionally increase precipitation and thermal forcing. A mesh convergence study with mesh sizes up to sub-kilometre scale is conducted to ensure our conclusions are numerically robust.

 

We increase the surface temperature by up to 8 degrees and the ocean temperature by up to 40 degrees with a range of different sliding laws. The migration of the grounding line positions, total ice volume and volume above floatation are calculated in order to determine if and where large scale retreat has occurred.