| Summary: | The Greenland ice sheet is one of the largest sources of cryospheric contribution to the global sea-level rise. The recent mass loss from the Greenland ice sheet is largely due to the increased meltwater runoff from the surface through supraglacial (on the top of the glacier) stream networks. Regional climate models are the primary tools for predicting Greenland’s contribution to sea-level rise; however, their validation is limited due to lack of in-situ observations of surface runoff through supraglacial stream networks. Moreover, these models do not capture the impact of some surface hydrological processes on runoff, leading to overestimation of modeled runoff from the ice sheet surface. This dissertation presents a novel data set that includes an unprecedented long record of stream discharge from a supraglacial catchment in southwest Greenland throughout almost an entire melt season. The study investigates stream discharge and its drivers while also examining how well the models simulate stream discharge. The results highlight the importance of meltwater routing through the dynamically changing stream network and temporary storage in the weathering crust for accurately modeling stream discharge. The research also reveals the sensitivity of stream discharge to sensible heat flux and albedo. This thesis shows that the regional climate/surface energy balance models are reasonably effective in simulating stream discharge near the ice margin of the ice sheet. However, to achieve high accuracy in modeled discharge, weathering crust needs to be considered as a model parameter to include density variations and subsurface storage in the weathering crust throughout the melt season in the ablation zone of the Greenland ice sheet. Furthermore, the thesis shows that even with coarser resolution models, large bias can be avoided as long as parameters such as ice fraction, elevation, and distance from the observation site remain representative of the site. This dissertation provides a deeper understanding of the factors ...
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