Abstract

The ice shelves bordering the Antarctic coastline play an important role in both the hydrography of the Southern Ocean and the mass balance and configuration of the Antarctic Ice Sheet. On the oceanographic side, ice shelves provide a surface boundary condition that is different than either open ocean or sea ice, with melting and freezing rates determined by small-scale turbulence and shelf-scale circulation, the latter in turn influenced by melting and freezing rates as well as ice shelf thickness. In some instances under-shelf processes significantly influence open-ocean hydrological and biogeochemical properties.

On the glaciological side, the ice shelves control the distribution of normal stresses at the grounding line, which in turn affects ice mass flux from the continent. Thus ice shelves provide a pathway for the heat content of the ocean to cause changes in continental ice sheets—which in turn feeds back on circulation by modifying the shape of the ice shelf cavity. In the case of rapidly-evolving ice shelves exposed to warm Circumpolar Deep Water, numerical modelling of such interaction presents a large challenge, since most ocean general circulation models (OGCMs) are not designed to allow for changing boundaries.

I will first present results from my own studies which examined such interactions using an old method of ice-ocean coupling—an “asynchronous” (or “dump-and-restart”) approach, and discuss the results of the study as well as strengths and weaknesses of the asynchronous approach and why it is not ideal as we move forward from process modelling to global predictions of coupled ice-ocean behaviour. I will then discuss the development of a new, synchronously-coupled ice sheet-ocean model, the difficulties and what is done to address them, and some preliminary experiments with this framework, yielding interesting results.

A common theme arising from the old work and new is the fact that, from the ice sheet stability perspective, ice shelf thinning due to melting is not solely important close the grounding line, as commonly thought, and may be vitally important to constrain and model in other regions of ice shelves commonly overlooked. Luckily, new observing platforms are being developed that may enable us to do just this.