Distribution Characteristics and Energy Balance of Ice Cliffs on Debris-covered Glaciers, Nepal Himalaya

Abstract

The ablation amount for entire ice cliffs reaches about 20% of that at the whole debris-covered area; the ablation rate at the ice cliff mainly depends on shortwave radiation, which differs widely with the orientation of an ice cliff. Therefore, the distribution of ice cliffs in relation to their orientation was observed on a debris-covered glacier. The south-facing cliffs were small in area because they have low slope angles and tended to be covered with debris. The north-facing cliffs, on the other hand, were large in the studied area and maintain a slope angle larger than the repose angle of debris. They, therefore, are stable. Longwave radiation from the debris surface opposite the ice cliffs was larger on the lower portion of ice cliffs than on the upper portion in every azimuth. This difference in longwave radiation maintained a steep slope angle on ice cliff. Shortwave radiation was stronger at the upper portion of ice cliffs than at the lower portion due to the local shading effect, causing gentle sloping of ice cliffs. This was especially pronounced at cliffs facing to south. Therefore, the dependency of the ice cliff angle in orientation can be explained by the difference in local radiation between the upper and lower portion of the ice cliff.