Abstract

On short length and time scales, ice behaves as a brittle, elastic solid but on continental length scales and timescales of years or longer, ice flows as a viscous fluid. The West Antarctic Ice Sheet, for example, sits on bedrock that is 1–2 kilometres below sea level. The ice itself is 4–5 kilometres thick in the central regions but thins as it flows towards the margins and eventually becomes thin enough to float on the ocean as a so-called ice shelf. The locus of detachment from the bedrock, where the ice sheet first starts to float, is called the grounding line. The position of the grounding line is determined dynamically, and there is concern to understand the conditions under which the grounding line would recede and allow the ice sheet to flow ever faster into the ocean, causing global sea levels to rise. I will present some simple fluid-mechanical experiments and mathematical models to address some of the fundamental physical balances that control the stability of grounding lines.