ABSTRACTThe paper examines the‘captured ice shelf’-hypothesis through the construction of a numerical model. Based on ice surface elevation, ice thickness, and ground topography, the velocity is calculated. The thickness is adjusted, taking into account the effects of mass balance and deformation.By calculating the fluid potential, the location of the water divide in theice rimaround thecaptured lakeis found (the water always flows towards the lower fluid potential). Within the water divide, the ablation is summed up and added to the volume of the captured lake. Thus, the captured ice shelf floats on a water surface which is above the threshold level. Should the water divide cease to exist, the captured lake will be emptied in a jökulhlaup.The results showed that a quick glacier advance is possible with this mechanism. However, the final equilibrium situation of the model runs do not seem to include any captured ice shelf. This is expected, since the captured ice shelf lacks a stabilizing feed-back mechanism—it is an unstable feature, with a life time probably in the range of a few thousands to several tens of thousands of years.