Rock glaciers in different climates: the Brooks Range, Alaska, and Swiss Alps

A rock glacier is a landform resulting from the complex input of debris, ground water, snow and glacial ice. In order to disentangle the complexity, I compare the distribution and structure of rock glaciers in different climatic conditions: the Brooks Range, Alaska, and Swiss Alps. Rock glaciers potentially develop between the snow line and the lower limit of permafrost. From this context, an arid environment has been sometimes argued to be favorable for the development of rock glaciers because of the large difference in elevation between the two boundaries. For example, rock glaciers are distributed more widely toward the southern part in the Swiss Alps where precipitation decreases from the north to south. In the Brooks Range, where the precipitation is about half of that in the southern Swiss Alps, the vertical range of the distribution is, however, similar to that in the Alps. The distribution of rock glaciers is topographically controlled below the low snow line in high latitude. The difference in precipitation in the two regions results in the different input patterns of snow. Burial of snow by rockfalls is thought to be one of the processes forming the internal ice of rock glaciers. In the Swiss Alps, snow reaches one to three m thick and it remains until the end of summer on the upper part of rock glaciers. In the Brooks Range, snow appears to rarely exceed one m thick and it disappears in early July except for the area close to the snow line. DC resistivity of rock glaciers, high values of which are a good indicator of massive ice in ground, is generally lower in the Brooks Range (10-50 kohmm) than the Alps (10-1000 kohmm). This result is contrary to the ground temperature but consistent with potential of snow burial. In the Brooks Range, high DC resistivity (>100 kohmm) was only observed on a rock glacier close to the present snow line. Such high resistivity is common in the Alps, even if rock glaciers originate from the foot of talus slopes lower than the snow line. These results from the Brooks Range are preliminary and further research will provide more information about the internal structure.