“…These include time-varying perturbations in local sea level (Gomez et al, 2012), accumulation, ice viscosity (Schoof, 2007), dynamism of bed friction (Sergienko and Hindmarsh, 2013) and changes in the stabilizing effect of the surrounding ice shelves (Gudmundsson, 2013;Wright et al, 2014) through basal melting induced by ocean temperature changes (Pollard and DeConto, 2009;Hellmer et al, 2012). Whether the readvance proposed in our revised model is due to external forcing (e.g., less warm water penetrating under the FRIS) or internal dynamics (e.g., GIA uplift leading to bed shallowing and grounding line readvance) is difficult to resolve by ice-sheet modelling owing to the sensitivity of grounding-line motion to melt, but either process could have operated here (Wright et al, 2014) or in other areas of the WAIS such as the Amundsen Sea embayment and the Ross Sea (Bindschadler et al, 1990;Catania et al, 2006). The possibility that some of these grounding lines might currently be advancing has implications for forecasting their response to warming associated with global change, as the initiation of unstable retreat would require changes in controls such as sub-ice shelf melt (Wright et al, 2014).…”