Vulnerability of firn to hydrofracture: poromechanics modeling

: On the Greenland Ice Sheet, hydrofracture connects the supraglacial and subglacial hydrologic systems, coupling surface runoff dynamics and ice velocity. Over the last two decades, the growth of low-permeability ice slabs in the firn above the equilibrium line has expanded Greenland’s runoff zone, but the vulnerability of these regions to hydrofracture is still poorly understood. Observations from Northwest Greenland suggest that when meltwater drains through crevasses in ice slabs, it is stored in the underlying relict firn layer and does not reach the ice sheet bed. Here, we use poromechanics to investigate whether water-filled crevasses in ice slabs can propagate vertically through a firn layer. Based on numerical simulations, we develop an analytical estimate of the water injection-induced effective stress in the firn given the water level in the