AbstractMicrobasin runoff experiments were conducted on ice surfaces of the Peyto Glacier during the 1971 and 2008 ablation seasons, when half‐hourly measurements of net radiation, wind speed, temperature, vapour pressure, and supraglacial runoff were obtained on warm sunny days with daily mean temperatures 6·1–10·1 °C and daily total ablation amounts of 43–95 mm. Net radiation contributed almost 70% of the melt energy in 1971 and nearly 60% in 2008, with the remainder supplied by turbulent transfers of sensible and latent heat. Thus, the two experiments are similar in finding that radiation dominates surface melt energy inputs to microbasin runoff outputs. They differ with respect to area definitions and microbasin shapes: (1) a purposely delineated rhomboidal area, 30 m long × 15 m wide, covering 386 m2 in 1971; (2) a naturally delineated elongated area, approximately 600 m long × 2 m wide, covering an estimated 1200 m2 in 2008. Three 24‐hour periods beginning at 0700 h were obtained for experimental work in 1971, and 8 such periods in 2008. Supraglacial runoff was modelled by passing melt energy water equivalents through a simple storage reservoir and forcing closure with measured runoff by optimising for delay time. Optimal times of 1–2 h were found for 1971, and 7·5–11·5 h for 2008, thus indicating a major difference between the runoff responses of the two microbasins. It is possible that different basin shapes may explain the contrasting delay times, perhaps because different shapes signify different flow connections to meltwater storage in the weathering crust. If the elongated microbasin response is typical of the elemental hydrological response unit of the melting ice surface, distributed glacier runoff models should incorporate it as part of the model structure. Copyright © 2011 John Wiley & Sons, Ltd.