E l e c t r o n i c   r e p r i n t


HYDRAULIC GEOMETRY
OF A SUPRAGLACIAL STREAM,

RAGNARBREEN, SPITSBERGEN

Andrzej Kostrzewski and Zbigniew Zwolinski

STUDY AREA

Field studies were made along a selected reach of one of the Ragnarbreen supraglacial streams. This glacier lies on the northern rim of the Petuniabukta, which closes the Billefjorden, one of the continuations of the Isfjorden on West Spitsbergen Island (Fig. 1). It is an outlet glacier (428 according to the code of the Fluctuations of Glaciers 1980-1985 (1988) or 423111 according to the code of the World Glacier Inventory (1989)), and flows between two non-glaciated massifs of Sfinksen and Hultberget. It is a branch of the Mittag-Lefflerbreen, which flows down the Lomonosovfonna. The length of the Ragnarbreen tongue attains a bit under 4.5 km; in the valley part its width averages 750 m, and its gradient, 0.085.


Fig. 1. Location of study area


The reach of the supraglacial stream under study ends some 500 m before the glacier front, its length is 700 m and mean gradient 0.08662. It is situated in the central (axial) part of the glacier, but a bit closer to its eastern margin (Fig. 1). On both its sides, in a radius of up to 100 m, other supraglacial streams, roughly parallel to the one being examined, could be observed. This observation of the Ragnarbreen and other glaciers of the Petuniabukta area (cf. also Knighton 1981, 1985) leads to the conclusion that the parallel pattern marking the network of supraglacial streams, and hence of their catchments of various orders, is their individual characteristic setting them apart from the networks developing in an alluvial substratum. This parallel pattern is due to the generally smooth glacier surface and its similar gradients over greater distances. Of no little significance is also the paucity or even absence of supraglacial morainic material that could force supraglacial streams to cut their channels differently. The channel under study joins another, larger supraglacial stream. In the vicinity of the stream and along the reach no subsurface flow was recorded.