Invited Talk by Ursula Rick

Surface meltwater retention in the accumulation zone of the Greenland Ice Sheet: Local effects, seasonal transport and their implications for mass balance

The fractions of surface melt retention and surface melt runoff on the Greenland Ice Sheet are important for mass balance models. In addition to the local retention, the lateral distance downslope that meltwater can travel before the end of the melt season is required for runoff calculations. A snowpack model simulates the effects multi-year cycles of melt, infiltration and refreeze have on snowpack physical properties, local retention, and downslope flow of meltwater. The local retention fraction calculated by the model is on the same order as previous studies (Pfeffer and others, 1991; Reeh, 1991; Janssen and Huybrechts, 2000), however the meltwater must travel out of the accumulation zone before winter freeze-up to be mass loss. The temperature conditions in the snowpack are the biggest control on the lateral distance that melt can travel. Any refreezing, from nightly to monthly, throughout the summer greatly inhibits the lateral transport of melt. In the area of this study, the West Greenland Ice Sheet, the maximum distance melt can travel downslope is about 15km.