Estimating Heat Transfer at Glacier Margins using Ground-Based Infrared Imagery

Abstract:

Tropical glaciers constitute an important water resource for downstream populations. However, our understanding of their physical processes is limited due to their high elevation and remote location. In order to gain information on the processes driving the ablation of tropical glaciers, we acquired time-lapse (5-10 minute interval) high-resolution (0.64 m² pixel size) infrared imagery of the Cuchillacocha Glacier in the Cordillera Blanca, Peru, in June 2014. This temperature dataset allows for the investigation of small-scale processes observed on the surface of the glacier and surroundings, such as the longwave transfer from the rock adjacent to the glacier. This process is particularly important for tropical glaciers, where the intense incoming solar radiation results in relatively high temperatures of the rocks adjacent the glacier and enhances longwave radiation emission. This radiative flux, varying between 81 and 120 W m^-2 daily, is affected by local shading but shows no significant dependency on elevation. The longwave flux derived from the infrared images is integrated into an energy-balance model of the glacier to compare melt at the glacier margin to that occurring on the surface of the glacier. We can then estimate the melt volume generated by this enhanced longwave radiation at the glacier margins during the dry season. Including the quantification of the longwave flux at the glacier margin results in an improved assessment of glacier energy budget and melt water generation of tropical glaciers.