Dynamics of subglacial floods

The Nye model of jokulhlaups is able to explain both their periodicity and even the detailed shape of the flood hydrograph. In this paper, we show how the model can be used to predict the shape of the hydrographs from the subglacial lake Grimsvotn beneath Vatnajokull in Iceland, and we comment on three particular issues that have proved contentious in the application of the Nye model: the role of water temperature; the shape of the flood channel; and the value of the bed roughness coefficient.