Subglacial discharge drives seasonal motion of the Barry Arm Landslide, Prince William Sound, Alaska

We investigated meteorological controls on seasonal deep-seated motion of the Barry Arm landslide, a ~500 Mm³ slope instability with tsunamigenic potential in Prince William Sound, Alaska. Using ground-based synthetic aperture radar, we identified periods of deep-seated displacement, and combined airborne ice-penetrating radar with a glacier melt model driven by local meteorological data to evaluate the role of Cascade Glacier, which covers much of the area contributing groundwater to the landslide. We show that an over-deepened section of Cascade Glacier adjacent to the most active part of the landslide likely acts as a transient reservoir that routes meltwater to the landslide and that deep-seated landslide motion initiated only when modeled glacier discharge exceeded a distinct threshold.