From Supraglacial to Englacial: Evolution of Meltwater Channels

Supraglacial channels as well as englacial conduits are integral parts of a glacier's hydrological system. Drainage of meltwater occurs through both, and their evolution is closely connected. Several mechanisms for englacial conduit formation have been proposed in recent literature and two involve supraglacial water streams. Englacial conduits may form either by incision of free surface streams flowing along the bottom of crevasses or by incision of supraglacial stream channels. Roof closure by ice deformation is integral to both conduit formation processes. Field evidence for supraglacial stream incision has been found in Svalbard and Nepal. In Iceland, where volcanic activity provides warm (T > 0 °C) meltwater, rapid enlargement of supraglacial channels has been observed. To investigate the evolution of supraglacial channels into englacial conduits, a numerical ice dynamic model is coupled to a hydraulic model including heat transfer. Ice deformation is simulated by a finite element model of a Stokes-Glen fluid, often referred to as a full Stokes model with a non-linear Glen rheology. As a first approach the hydraulics of open channel flow are approximated by the well known Manning formula and a simple heat transfer model from water to ice walls is assumed. The usefulness of more complex hydraulics and heat transfer models for better simulation of the coupled system is investigated and results for different starting geometries, water temperatures and water fluxes are presented.