Observations in a Cold Ice Cap

Abstract

In the approximately so m. thick ice cap of the Jungfraujoch (3470 m. above sea level), where the temperature throughout lies below the pressure melting point, continual measurements of displacement and deformation were carried out inside ice tunnels from 1950 onwards. These give an insight into the process of movement, the formation of water-filled crevasses and the relationships of viscosity in a cold ice cap glacier.The plastic behaviour of the cold ice was examined through alterations in length of individual tunnels, and also through measured distortions of cross-section in circular sections of tunnel. Since the mean ice temperature in the region of the ice tunnel lies approximately between −1° and −3° C., these examinations provide a welcome supplement to analogous measurements which were taken in circular tunnels in a temperate glacier (Z’Mutt tunnel). The approximate calculation of the plastic deformation of a circular tunnel was thus extended by the obvious transformation of solutions known from elasticity theory.By means of a qualitative analysis of the state of stress of an ice cap, an attempt is made to account for the distortion and the formation of the cracks and crevasses which were observed. The occurrence of blue bands could be followed in statu nascendi. This paper serves as a primary orientation and publishes some initial results of the examinations which are to be continued and completed over a number of years. In addition to its potentialities for practical use, this study may be of interest in respect to the behaviour of cold glaciers of the Arctic and Antarctic. In a final section, therefore, some problems of the Greenland ice sheet are considered in the light of the preceding conclusions.