AN OBSERVATION OF ROLL WAVES IN A SUPRAGLACIAL MELTWATER CHANNEL, HARLECH GLACIER, EAST GREENLAND

Observations of pulsating flow conditions in a supraglacier meltwater channel on Harlech Gletscher, East Greenland, are reported. Waves of water with turbulent wave fronts and smooth recessive limbs were observed passing downstream at regular intervals of 6-7 s. Peak channel discharge was estimated at 0.5-1.0 m3 s-1, in between which discharge was zero. It is suggested that the phenomenon as observed was due to the formation of roll waves in response to channel morphology and prevalent discharge conditions. Measurements of channel morphology are given together with calculations of critical flow conditions, supporting the hypothesis of roll waves in a natural ice channel. A brief introduction to roll waves and the theory regarding their formation is included.