Abstract ID: 3.11381 | Accepted as Poster | Talk/Oral | TBA | TBA

We present a model for water flow at the base of a glacier implemented with the Elmer/Ice Open-Source Finite-Element Software. The model describes subglacial water flow in connection with the emptying of basal water bodies and the subglacial propagation of glacial lake outburst flood (jökulhlaup) fronts using a visco-elastic model for the overlying glacier combined with a turbulent thin-sheet model for water flow. Glacial lake outburst floods include some of the largest documented floods on Earth and are among the most important geomorphological processes in watersheds downstream from glaciers. Such floods from subglacial geothermal areas, marginal lakes and subglacial volcanic eruptions are common in Iceland and they pose a substantial hazard to settled areas as well as to roads, communication lines and other infrastructure near glaciers. The visco-elastic model is based on Maxwell-elements combining linear elasticity with the non-linear viscous behaviour described by Glen’s ice-flow law, and, by introducing a pressure variable, allowing for incompressibility of the material. The dynamics of the subglacial ice–water interface is implemented as fluid–structure interaction (FSI), utilizing artificial compressibility. The coupled visco-elastic, thin-sheet water-flow model aims to represent the propagation of rapidly- and slowly-rising subglacial floods, many of which are inferred from remote-sensing and in-situ observations to involve lifting of the glacier from its sole over large areas. Dynamically similar subglacial ice–water interactions may be involved in widespread, propagating ice-velocity and surface-elevation disturbances that have been observed by remote sensing during subglacial drainage events in Greenland and Antarctica, indicating that the dynamics of jökulhlaups may have wider implications for glacier dynamics in general. We will demonstrate the coupled model with simple synthetic examples. The visco-elastic model can simulate the observed geometry of ice-surface depressions formed by the collapse of basal water cupolas and conduits, for which we present simulation results with comparison to observed ice-surface depressions at Vatnajökull ice cap, Iceland.