Spatiotemporal Dynamics of Solar Radiation in the Himalaya: Topographic Forcing and Glacier Dynamics

Abstract

Glaciers across the Himalaya exhibit significant spatial variations in morphology and dynamics. Climate, topography and debris cover variations are thought to significantly affect glacier fluctuations and glacier sensitivity to climate change, although the role of topography and solar radiation forcing have not been adequately characterized and related to glaciers. Analyzed are a set of glaciers in the Karakoram mountain range, where a clustering of surge type glaciers occurs. The objective of this works is to investigate topographic effects on glacier state, such as if a glacier is of surge type or not, and if a glaciers is retreating or advancing. Specifically, the focus of this work is the spatiotemporal effects of solar radiation on glaciers as modulated by the topography. A geomorphic assessment of the glaciers is also performed, so that solar radiation forcing could be studied in the appropriate context. A rigorous GIS-based solar radiation model that accounts for the direct and diffuse-skylight irradiance components was developed and applied for an ablation season over the study area. The model accounts for multiple topographic effects on the magnitude of surface irradiance. Enhanced ablation was determined to be a distinguishing characteristic of surge type glaciers as indicated by the positive relation between ablation-season surface irradiance and the probability of a glacier being of surge type, as well as by the positive relation between lesser topographic shielding and the probability of a glacier being of surge type. These results demonstrate the important role that local and regional topography plays in governing climate-glacier dynamics in the Himalaya.