Heat transfer from the water can cause sufficient melting to create an air-filled cavity, sometimes aided by solifluction.
The water flow must dissipate enough heat to keep the glacier ice refreezing in polar areas.
Air movement can then assist enlargement through melting in summer and sublimation in winter.
The downward infiltration are made of flow of melting superice in glacial systems.
Some glacier caves are formed by geothermal heat from volcanic vents or hotsprings beneath the ice.