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Glacier surface roughness and ablation patterns

Glacier surface roughness and ablation patterns

As part of research looking to improve glacier mass balance modelling led by Jo Nield, and supported by the Royal Society, a group of us worked at Svinafell, Iceland for two weeks over summer 2011. Along with Jo and I, Steve Darby, Richard Chiverrell and two undergraduate assistants undertook repeat laser scans of ice surfaces in conjunction with direct measurements of aerodynamic roughness using bespoke wind tower setups.

Glacier melting is predicted by determining radiative and turbulent heat fluxes at the glacier surface. The theoretical basis for modelling these fluxes is well understood, but prediction is hampered by difficulties in parameterising key controlling factors at high spatial resolution. Surface roughness in particular has a strong influence on turbulent heat exchange, but measurement is problematic. This project uses TLS to determine the changing topography of a melting glacier. Crucially, TLS delivers topographic data of unprecedented precision and spatial resolution, enabling surface roughness to be obtained via statistical analysis of the measured elevation. Concurrent measurements of aerodynamic roughness heights have also been derived from analysis of vertical wind velocity profiles obtained using anemometer towers for comparison to the surface based measurements. This study expands current knowledge regarding the way in which spatial variations in surface topography influence aerodynamic roughness and its contribution to glacial energy budgets and ablation. Improved parameterisation of roughness will thus aid mass balance modelling.