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

FINAL CONCLUSIONS

The research carried out on the Ragnar glacier, despite its fragmentary nature, can be regarded as useful both for glaciology and fluvial geomorphology. The discussed subject calls for detailed studies of a lot of factors - climatic, hydrological, glacio-hydrological, physical-chemical, morphological, and with some glaciers, also lithological, so well manifested in the supraglacial water flow. The presented analysis of hydraulic geometry parameters can provide a model for investigations of ablation processes on glacier surfaces, not to mention a detailed interpretation of a number of specialised issues in glacial hydrology or fluvial geomorphology.

The 3-stage development model of a supraglacial channel presented above seems convincing. It reflects the short-term variations in the ablation regime, which in turn bring about specific morphological effects that can be traced using hydraulic geometry relations. With reference to downstream hydraulic geometry, these relations can be expressed in quantitative terms for the successive stages in the development of a supraglacial channel as follows:

  1. b < f,
  2. b > f,
  3. m --> about 0.
When placed on Rhodes' (1987) b-f-m diagram, the exponents make up the following sequence:

The reservation that has to be made at this point is that the above regularities refer to supraglacial channels newly developed on a glacier surface. In the case of years-old recovery channels, one might expect different quantitative results concerning their hydraulic geometry. The study of ablation in relation to supraglacial streams make it possible to capture changes in the development of the glacier surface relief. The proposed model of the evolution of supraglacial channels has yet to be tested in detail against physical and chemical properties, mainly thermal, of glacier ice and meltwater, as well as measurements of the parameters of at-a-station and downstream hydraulic geometry throughout the ablation season. It is necessary to conduct further detailed studies to gain a better understanding of the spatial nature of ablation processes down the long profile of a glacier, and of the temporal variations in the ablation regime at various time scales. It would be interesting to carry out this research in a variety of variants of the cold climate and on a variety of glacier types.