Abstract

Recent theories of the coastal flow of ice sheets have proposed that there is a boundary region where the stress within the ice makes a transition from extending flow, characteristic of ice shelves, to shearing flow, characteristic of the grounded ice sheet. The details of this transition have recently been illuminated by three new theories, each corresponding to a distinct limiting case (Schoof, 2007; http://www.eos.ubc.ca/~cschoof/groundingline.pdf). To apply these mathematical advances in predicting the Antarctic contribution to sea level we need to know which theory most closely resembles the real world. Another complication is that, in plan view, grounding lines are curves, not straight lines, so we will also need to extend the theory from two dimensions to three. This talk gives some background to the problem of predicting the ice sheet, introduces the recent theoretical research on grounding lines, and presents some satellite and airborne observations from the Amundsen Sea sector that can help us to choose the appropriate limiting case for this part of West Antarctica. It also describes some progress towards extending the theory to 3D, beginning with an axisymmetric ice sheet. The axysymmetric model can describe laterally diverging flow (with ice flowing radially outwards towards an ocean) or laterally converging flow (where the ice flows radially inwards towards a small central ocean). The latter case provides an analogue for inwardly curved embayments, such as Pine Island Bay.