IngentaConnect Determination of basal hydraulic systems based on subglacial high...

Authors: Lappegard, Gaute; Kohler, Jack

Source: Annals of Glaciology, Volume 40, Number 1, January 2005 , pp. 37-42(6)

Publisher: International Glaciological Society

Abstract:

We have conducted short-term pump experiments with pump pressures exceeding ice overburden to study the seasonality of the subglacial hydraulic system of Engabreen, Norway. Data were collected from load cells installed flush with the ice-bedrock interface and pressure transducers installed in boreholes leading from bedrock tunnels underneath the glacier to the ice-bedrock interface. The water-pressure recordings, seen in relation with the load-cell record, show the existence of hydraulically connected vs unconnected bed areas. Monitored boreholes have been used to inject water at high pressures. Each experiment led to the growth of a high-pressure water cavity whose spatial extent could be inferred from load-cell and pressure transducer records. Post-pump pressures were low after summer pump tests and close to ice-overburden level after winter pump experiments. We conclude that drainage takes place in a fast-flow, low-pressure, channel-based drainage system during summer, and a low-flow, high-pressure, linked-cavity drainage system during winter.

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Determination of basal hydraulic systems based on subglacial high-pressure pump experiments