Stability of ice sheets and their response time to intrinsically or extrinsically forced changes has been in debate. The possibility of future collapse of the West Antarctic Ice Sheet (WAIS) has been one of the ominous scenarios considered as a legitimate, though as yet unquantifiable long-term potential threat, by the Intergovernmental Panel on Climate Change (Houghton et al., 1996) among other groups (Oppenheimer, 1998). Geological evidence from beneath the ice sheet, in particular microfossil and cosmogenic isotope data, have demonstrated that the WAIS has a history of Pleistocene disintegration, confirming the potential of the ice sheet to retreat well beyond the current configuration, and subsequently re-form (Scherer et al., 1998), though the actual speed of past "collapse" remains unknown. Recent integrated ice sheet - ice shelf - sea ice - ocean modeling efforts (Bougamont et al., 2004) will improve our ability to recognize past WAIS collapse events from marine stratigraphic records, which will help refine the frequency and rate of past collapse events.

Early ice sheet models indicated that the dynamics of the glacier and water depth near its grounding line, where submarine grounded ice goes afloat as either an ice shelf or floating glacier-tongue, may be critical in terms of stability (e.g. Hughes, 1973; Weertman, 1976; Thomas, 1979; Thomas et al., 1979). More recent larger models conclude that it may not be as critical (van der Veen, 1985; Hindmarsh, 1993; Hindmarsh and Le Meur, 2001). Huybrechts (2004) points out that the reality of the WAIS is much more complex than the models represent and the complete mechanisms and their response times to changes are not well understood (refer to summaries of these debates in Bindschadler and Bentley (2002) and Bentley (2004)). Perhaps the current state of analysis is best summarized by Vaughan and Spouge (2002) using a risk assessment approach with a panel of experts. The panel noted that "...different workers have very different opinions about the relative importance of particular mechanisms in controlling the likely future behaviour of WAIS-collapse. In principle, progressive scientific research and debate should proceed toward consensus over which theories are valid. In practice, such a consensus has not yet been reached in relation to WAIS collapse." Furthermore, they concluded that "The divergent views of the panel about the likelihood of WAIS-collapse and the mechanisms that may cause it reflect genuine scientific uncertainty about this issue, and cannot be simply resolved without further research. Increased understanding of the physics of the problem will reduce the epistemic uncertainty in the estimate."