| Summary: | Meltwater produced on the Greenland Ice Sheet (GrIS) surface is routed through complex networks of supraglacial streams across the ice surface. Most of the supraglacial streams on the GrIS terminate into moulins. Moulins are vertical conduits that penetrate through the entire ice thickness and deliver meltwater to the ice sheet's bed where water pressure fluctuations can modulate sliding speed. A poorly constrained parameter in glacial hydrological models is the timing and the volume of meltwater entering moulins within the GrIS ablation area. Here, we present direct measurements of supraglacial stream discharge within six catchments within the GrIS ablation area during the 2017 and 2018 melt seasons. In 2017 we measured stream discharge using a fluorescent dye dilution method. We continuously injected a Rhodamine WT solution (known concentration and pumping rate) into supraglacial streams and measured the dye concentration with a Cyclops fluorometer installed 50-100 meters downstream of the dye injection site. In 2018 using a continuous wave Doppler flowmeter (Teledyne ISCO 2150) that was installed on the stream's floor. We then use these measurements to model catchment discharge from runoff data (Mejia et al., 2021) using the synthetic unit hydrograph, following the methodology described by King 2018.
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