Alpine subglacial hydrology

The size and shape of subglacial flow pathways exert a strong influence over the pressure and speed at which meltwaters are routed through glaciers. These characteristics, in turn, influence glacier sliding velocity and the quantity and quality of bulk meltwaters discharging from glaciers. In this paper we summarise four empirical research approaches that have been developed to improve our understanding of the subglacial hydrology of predominantly temperate-based, alpine glaciers: investigations of bulk meltwater discharge and chemistry; tracer studies; proglacial bedrock investigations, and borehole investigations. As a result of linking these studies to conceptual or numerical models, three arborescent and four non-arborescent, or distributed, subglacial drainage configurations are described. These drainage networks may be neither spatially nor temporally persistent, but may compete with, and replace, each other on a seasonal basis. A qualitative model of the temporal and spatial evolution of a typical alpine subglacial drainage system is advanced on the basis of research conducted at Haut Glacier d'Arolla, Switzerland.