Fine-scale ocean processes in the basal melting of Antarctic ice shelves

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• Madi Rosevear, University of Tasmania
• Wednesday 02 December 2020, 10:00-11:00
• British Antarctic Survey, Zoom.

If you have a question about this talk, please contact Dr Irena Vankova.

The talk will be online. Contact the host to get Zoom details.

The Antarctic Ice Sheet, which comprises the largest volume of ice on our planet, is losing mass due to ocean-driven melting of its fringing ice shelves. Efforts to represent the effects of basal melting in sea level projections are undermined by poor understanding of the turbulent ice shelf-ocean boundary layer (ISOBL), a meters-thick band of ocean that regulates heat and salt transfer between the ambient ocean and the ice. Ocean-climate models cannot resolve the ISOBL and rely on parameterisations to predict melting. However, observations suggest that common ISOBL parameterisations only perform well in cold, energetic ocean environments.

In this talk I will summarise some of the main findings of my PhD thesis, which uses both observational data and turbulence-resolving model simulations to characterise melting and ISOBL dynamics across a broad range of ocean states. The observational data comprises unique ocean and in situ basal melt rate observations from beneath the Amery Ice Shelf. The modelling focuses on the ISOBL and is performed using resolved large-eddy simulation. The model domain consists of a horizontal ice-ocean interface underlain by a stratified ocean, and is forced by a steady flow in geostrophic balance. Using these model simulations, I investigate the coupled ISOBL and melting response to ocean temperature and current forcing. Depending on the relative strength of the thermal and current forcing, I find that the ISOBL may be characterized as either “well-mixed” , “stratified” or “double-diffusive”. I use these results to develop a novel regime diagram for the ISOBL , which provides new insight into the varied and nonlinear melting responses expected around Antarctica, depending on the local conditions. Comparison to observed sub-ice shelf conditions and melt rates is favorable and demonstrates the relevance of these regimes over a broad range of realistic conditions.

This talk is part of the British Antarctic Survey - Polar Oceans seminar series series.

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