Analysis of Snow Line and Albedo Conditions By Means of Time-Lapse Photography on Tapado Glacier, Chile

Abstract:

In the semiarid Coquimbo Region of Chile, high-altitude glaciers and seasonal snow are important sources of freshwater for irrigated agriculture and urban consumption. Due to the aridity of the environment, losses due to sublimation are large which means that accurate melt modelling is essential in order to reliably estimate streamflow. Since 2008, the CEAZA glaciology group has been studying the energy and mass balance of the largest glacier in the catchment, the Tapado Glacier using field and remote sensing measurements, and numerical modelling. The Tapado glacier system (30°08' S, 69°55' W) is a complex assemblage of uncovered and debris-covered ice located at the head of the Elqui basin between 4500 and 5536 m a.s.l. Energy balance modelling studies at the site have been limited in scope due to the development of ice pinnacles or penitentes on snow and ice surfaces. These features complicate energy distribution across the surface, due to modifications of parameters such as albedo. In this paper, we use time-lapse photography and automatic weather station (AWS) measurements to investigate how the development of penitentes impacts the spatial and temporal variability of albedo across the glacier surface and whether terrestrial photography is appropriate for use at such locations. Oblique photographs obtained from a high vantage point were georeferenced using a high resolution digital elevation model available for the entire glacier and its environs. By comparing the photographic data with point albedo measurements made at an AWS, distributed albedo maps were produced. Preliminary results suggest that distributed albedo values may be underestimated by the formation and development of penitentes during the ablation season. Moreover, it was observed that the evolution of the snow line during summer was not only topographically controlled but also modified by occasional convective snowfalls. Time-lapse photography provided to be a cost-effective tool for monitoring remote and high-altitude glaciers at high temporal resolution.