Radio-echo sounding determination of polythermal glacier hydrology

In this paper we describe three sources of information that radio-echo sounding has provided about the subsurface hydrology of a polythermal glacier: 1. Water input locations: crevasses and moulins provide the main pathway for surface melt to reach the interior of the glacier, and are identifiable as strong reflectors close to the glacier surface. 2. Subglacial flow routing: common mid-point surveys are used to calculate the radio-wave velocity through the glacier. Reflections from the glacier bed are then converted to ice depths, which are subtracted from the surface topography to determine bed topography. These are used to reconstruct the subglacial hydraulic potential surface and likely patterns of basal water flow. 3. Subglacial properties: repeat surveys at the same location over 9 days display diurnal variations and changes in bed reflection power associated with changes in basal water flow.