- 1ENS de Lyon, CNRS, LPENSL, UMR5672, 69342, Lyon cedex 07, France
- 2CNRS, ENS de Lyon, LPENSL, UMR5672, 69342, Lyon cedex 07, France
- 3ACCESS-NRI, Australian National University, Canberra, Australia
- 4Université Claude Bernard Lyon 1, ENS de Lyon, CNRS, LPENSL, UMR5672, 69342 Lyon cedex 07, France
While East Antarctica ice shelf cavities are currently filled with cold surface water and experience low basal melting, West Antarctica ice shelf cavities are filled with warm Circumpolar Deep Water (CDW) and experience high basal melting. Recent modeling studies have shown that cavities currently filled with cold water may suddenly transition to warm water conditions under climate change scenarios. However, the dynamical drivers of such regime changes are poorly understood, such that the likelihoods of ocean cavities tipping from cold to warm conditions on sea levels and global ocean circulation are still uncertain.
Recent studies have used conceptual box models to propose a mechanistic explanation for the transition from a low melt rate regime (due to cold, saline surface water filling the cavity) to a high melt rate regime (driven by CDW intrusions) in specific ice shelf cavities [1,2]. Here, we extend an existing conceptual model to study these regime shifts. This new model takes into account polynya convection thanks to a sea surface box at the front of the ice-shelf, but also ice shelf/ocean interactions as in the Potsdam Ice-shelf Cavity model (PICO) [3] to generically study various Antarctic ice shelves. We find that numerous ice shelf ocean cavities are in a bistable regime and check that the results are robust against changes in model parameterizations. The surface box enables a representation of the impact of polynyas on dense water formation, which we demonstrate plays a key role in the bistable dynamics of under-ice-shelf seas. Our results suggest that the melt rate of ice shelves might vary abruptly under weak atmospheric changes.
[1] J. E. Hazel, A. L. Stewart, Bistability of the Filchner-Ronne Ice Shelf Cavity Circulation and Basal Melt. J. Geophys. Res. Ocean. 125, 1-21 (2020).
[2] R. Moorman, A. F. Thompson, E. A. Wilson, Coastal polynyas enable transitions between high and low West Antarctic ice shelf melt rates. Geophysical Research Letters. 50, 16 (2023).
[3] R. Reese, T. Albrecht, M. Mengel, X. Asay-Davis, R. Winkelmann, Antarctic sub-shelf melt rates via PICO. The Cryosphere. 12(6), 1969-1985 (2018).
How to cite: Saddier, L., Herbert, C., Bull, C. Y. S., and Couston, L.-A.: Bistable Dynamics of Ocean Circulation under Antarctic Ice Shelves: Insights from a Low-Dimensional Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4369, https://doi.org/10.5194/egusphere-egu25-4369, 2025.
