Melt Processes at Glacier Margins: High-Resolution Ground-Based IR Imagery in the Cordillera Blanca, Peru

English Abstract:

Alpine glaciers provide water resources to some of the most populated regions on Earth. However, these resources are threatened by ongoing and accelerating glacier retreat. To properly understand the impact of this retreat on water resources downstream, we need to understand the processes driving the ablation of these headwater glaciers. Due to their remote location and often complicated access, obtaining in-situ, glacier-wide data for alpine glaciers is challenging. An emerging technique to investigate melt processes in these complex settings is ground-based infrared imagery. Infrared images, captured simultaneously with traditional weather stations monitoring on and off the glacier, can be processed to obtain high spatial and temporal resolution temperature maps of the glacier surface. This spatially distributed temperature data allows for the investigation of small scale surface processes such as the impact of surface cover and temperature gradient at glacier margins. These processes are investigated for a tropical glacier in the Cordillera Blanca, Peru. Daily time-lapse infrared imagery (5-30 minute spacing) of the glacier and close-up images of the margin, were acquired for the 2013 and 2014 dry season. The results indicate that the temperature gradient between the surrounding rocks and the glacier margins is highly dependent on topographic shading in addition to atmospheric and meteorological conditions. In clear sky conditions, incoming shortwave radiation heats the exposed rock faster than the adjacent ice, leading to a net radiation flux toward the glacier. This effect is also seen in late afternoon, when there is no more direct solar forcing. These energy transfers at the glacier margins appear to be a small but significant contribution to the overall melt generation for small alpine glaciers. This study shows the potential utility for collecting and analyzing ground based infrared imagery for glacier studies, with implications for hydrologic and water resource applications.