The internal drainage system of the lower Mittivakkat Glacier, Ammassalik Island, SE Greenland

Abstract

Geografisk Tidsskrift, Danish Journal of Geography 106(1):13–24, 2006 A dye-tracer technique was used to examine the spatial and the temporal size, structure and hydraulic response of the internal drainage system in the lower ablation area of the Mittivakkat Glacier, southeast Greenland. Eight dye-tracer tests were conducted at five active moulins during the last part of the ablation period, August 2004. The internal drainage system, about 300–685 m from the glacier terminus, consisted of two distinct internal drainage paths: one through a hydraulically efficient channelled (fast) drainage system, and another through a relatively hydraulically inefficient distributed (slow) system. The internal drainage system 0–300 m from the glacier terminus was drained by one conduit. It was observed that 100 m from the glacier watershed divide, dye return curves indicated transport of englacial and subglacial water to the nearby glacier catchment. Spatial transit velocity (fastest, dominating, and median transit velocities) decreased with increased transit distance, due to increased complexity and transit delay in the internal drainage paths; the fastest transit velocities variedfrom 0.18 to 0.37 m s−1, dominating transit velocities from 0.10 to 0.27 m s−1, and median transit velocities from 0.08 to 0.20 m s−1. The diurnal transit velocity increased with increasing discharge and vice versa, indicating a clockwise velocity-discharge hysteresis.