Evaluating a method of thermal infrared remote sensing of sub-debris ice ablation: Emmons Glacier, Mount Rainier, Washington

Supraglacial debris complicates the energy balance at the glacier-atmosphere interface, making mass balance modeling difficult for debris-covered glaciers. Thermal infrared (TIR) remote sensing can supply debris surface temperatures to drive energy balance models, but the spatial resolution of satellite TIR instruments, such as Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), is poor. In a field plot on Emmons Glacier (Mount Rainier National Park, Washington), comparable in size to a single ASTER pixel, we measured ablation rates ranging from 10.9 to 30.1 cm/day under debris thicknesses ranging from 3 to 44 cm and with textures ranging from sand and gravel to large boulders with open pore space. A simplified energy balance model driven by debris surface temperature was developed to estimate measured ablation rates despite variations in debris thickness and texture. Modeled ablation rates adequately matched measured ablation rates. Meter scale variations in ablation such as those we measured cannot be resolved in satellite TIR imagery, but have potential to be captured in near ground or unmanned aerial vehicle (UAV) TIR imagery. To test a method of near-ground TIR remote sensing, four test plots of approximately 1 m2 were constructed in the center of the field site. Debris surface temperatures were measured for each plot, and compared well to debris surface temperatures derived from highly accurate thermistors. Ablation modeling from near ground or UAV TIR imagery holds promise for future debris-covered glacier modeling in remote areas