Warm mode melt impact on ice dynamics in Antarctica

The Antarctic Ice Sheet is losing mass, a large part of which is due to ocean melting under ice shelves. Current projections from the ISMIP6 project show a gradually warming ocean forcing in currently cold cavities, but there is a growing literature that this may not be an accurate representation of how the temperatures beneath the ice shelves will change. Instead, the cold Antarctic ice shelves – like Filchner-Ronne or Ross – are expected to experience an intrusion of warmer circumpolar deep water under strong climate forcings. This has the potential to shift the regime of the Antarctic basins from cold to warm states, leading to increased melt rates. 

Here, we focus on three of the currently cold-based basins, namely Filchner-Ronne, Amery, and Ross. Using the literature of likely timings for regime shifts for each of these cavities, we investigate how an immediate temperature change at these timings compares to the gradual warming beneath the cavities modelled in the ISMIP6 simulations. We create an ocean forcing using the warm mode temperature anomalies from Nicola et al., (2025) to represent the regime change in these basins and run simulations using the numerical ice sheet models Ua and PISM, coupled with the ice sheet cavity box model PICO. Then, we compare the model outputs to simulations using the original CMIP6 ocean forcing.

Nicola, L., Reese, R., Kreuzer, M., Albrecht, T., and Winkelmann, R.: Bathymetry-constrained warm-mode melt estimates derived from analysing oceanic gateways in Antarctica, The Cryosphere, 19, 2263–2287, https://doi.org/10.5194/tc-19-2263-2025, 2025.