Runoff response time of a loosely defined supraglacial microbasin

Abstract. A micrometeorological experiment was conducted in the summer of 2008, at Peyto Glacier, during four meltwater production periods of 1, 3, 4 and 5 days duration, the last two days marked by late summer snow cover. The data include a breakdown of net radiation into its short- and long-wave components, as well as wind speed, temperature and humidity profile data for use in bulk transfer estimates of sensible heat and moisture transfer. In addition, a hydrological experiment was conducted, the data comprising sonic sounder measurements of ablation and stage level records of discharge from a supraglacial microbasin. As expected, the ratio of daily average runoff flow measurement to energy budget flow estimates is less than one on most days because of weathering crust development. Also, the conversion of stage level data into discharge from a supraglacial catchment presents challenges, notably defining the area of a loosely defined basin and specifying stage level on a downward moving surface. Nevertheless, it is clear that peak discharge lags peak meltwater energy input by periods of four to six hours. A suitably lagged flow estimate can be achieved by passing the flow through a simple storage reservoir, using delay times of 14.5, 15, 7.5 and 9 h for each respective measurement period. This suggests that a substantial part of the delay in runoff from a glacier basin is tied up in ice surface hydrological processes.