Geophysics PhD Defense, Josh Rines: "Greenland supraglacial lake drainage events: modeling and observations"

The dynamics of the Greenland Ice Sheet are sensitive to the presence of meltwater at the ice-bed interface, which modulates the frictional coupling between the ice and the bed below. One mechanism by which meltwater reaches the bed is via full-thickness surface-to-bed pathways, such as moulins and fractures. These pathways route meltwater generated at the surface during the warmer summer months to the bed, where it joins with the subglacial hydrological system and impacts basal sliding and overall ice dynamics. One mechanism by which these surface-to-bed pathways form is via hydrofracture-driven supraglacial lake drainage, wherein a meltwater lake on the ice surface drives a fracture to the bed, depositing the entire volume of the lake at the ice-bed interface. Upon arrival, this water reduces the basal frictional coupling over a spatially finite region, which subsequently changes the stress state in the overlying ice. An active conversation in the literature is: what is the character of this change in stress, can it influence other such events, and where do these events occur in the first place? It is to each of the three threads of this conversation that the work in my thesis contributes, chapter by chapter.