Glacier hydrology informed ocean circulation enhances channelised basal melting beneath the Petermann Ice Shelf

Seasonal increases in subglacial discharge profoundly impact ocean-driven melting of the Petermann Ice Shelf, yet the influence of discharge magnitude and emergence location on melt remains unclear. We use a regional 3-D ocean model of Petermann Fjord with realistic seafloor and ice-shelf geometry, forced by discharge from a subglacial hydrology model of the Petermann Glacier catchment. Two experiments are performed: (a) a control run with uniform grounding-line discharge, and (b) a realistic run routing equivalent discharge through hydrologically informed outlets. Buoyancy forcing concentrated along eastern and western ice shelf basal channels in the realistic run produces locally enhanced plume-driven circulation, which is laterally confined by the narrow and steep channel walls, driving up to 53% increase in channel-averaged summer mean melt. Local summer mean melt rates rise by up to 78 m/yr near the grounding line, where plumes are most energetic, and decline downstream as the plume velocity reduces. Power‐law fits reveal that a unit increase in discharge yields greater melt in the western channel, and channel geometry, and discharge magnitude and routing modulate the melt-discharge relationship. A free power‐law fit significantly outperforms a fixed square‐root dependence, underscoring that ocean-ice simulations must account for hydrologic, topographic, and rotational controls to constrain future sea‐level projections.