Sensitivity of grounding zone melting to subglacial discharge configuration and sediment dynamics across contrasting ice shelf cavity regimes

Abstract. Subglacial freshwater discharge plays a critical role in modulating basal melting and ocean circulation beneath ice shelves, yet the combined influence of discharge configuration, cavity thermal state, and sediment-driven morphodynamics remains poorly constrained. Using idealised ocean simulations following the ISOMIP+ framework, we investigate how subglacial discharge location, configuration (channelised versus distributed), and sediment load interact with contrasting warm and cold cavity regimes, and how these processes influence the circulation, melt, and seabed evolution at the grounding zone. Melt rates differ markedly between warm and cold regimes, with values in the warm cavity an order of magnitude higher than in the cold cavity. However, relative to no-discharge control experiments, subglacial discharge induces substantially greater local melt anomalies at the grounding line in the cold cavity, where localised melt rate increases up to ~955 %, compared to ~173 % in the warm regime. Discharge location and configuration further control the spatial extent of the response, with channelised inputs driving strong, localised melting, and distributed inputs producing weaker but more spatially extensive melt across the grounding zone. Sediment-laden subglacial discharge consistently reduces localised melt under channelised configurations (~13 % reduction in the warm regime and ~16 % in the cold regime), whereas its influence is negligible (<1 %) when discharge is distributed. These reductions arise primarily through morphodynamic feedbacks, as sediment modifies seabed structure and circulation near the grounding zone. In the cold regime, reduced circulation promotes sediment accumulation and episodic erosion, leading to seabed and circulation changes. These results demonstrate that the impact of subglacial discharge on basal melt depends on the combined effects of cavity regime, discharge configuration, and sediment dynamics, with implications for representing grounding zone processes and basal melt parametrisations in ice-ocean models, and ultimately for ice shelves vulnerability and Antarctic Ice Sheet stability.