Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 10, 1897-1913, 2016
http://www.the-cryosphere.net/10/1897/2016/
doi:10.5194/tc-10-1897-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
02 Sep 2016
3-D surface properties of glacier penitentes over an ablation season, measured using a Microsoft Xbox Kinect
Lindsey I. Nicholson1, Michał Pętlicki2,3, Ben Partan4, and Shelley MacDonell3 1Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
2Institute of Geophysics, Polish Academy of Sciences, ul. Księcia Janusza 64, 01-452 Warsaw, Poland
3Centro de Estudios Avanzados en Zonas Áridas (CEAZA), La Serena, Chile
4University of Maine, Orono, USA
Abstract. In this study, the first small-scale digital surface models (DSMs) of natural penitentes on a glacier surface were produced using a Microsoft Xbox Kinect sensor on Tapado Glacier, Chile (30°08′ S, 69°55′ W). The surfaces produced by the complete processing chain were within the error of standard terrestrial laser scanning techniques, but insufficient overlap between scanned sections that were mosaicked to cover the sampled areas can result in three-dimensional (3-D) positional errors of up to 0.3 m. Between November 2013 and January 2014 penitentes become fewer, wider and deeper, and the distribution of surface slope angles becomes more skewed to steep faces. Although these morphological changes cannot be captured by manual point measurements, mean surface lowering of the scanned areas was comparable to that derived from manual measurements of penitente surface height at a minimum density of 5 m−1 over a 5 m transverse profile. Roughness was computed on the 3-D surfaces by applying two previously published geometrical formulae: one for a 3-D surface and one for single profiles sampled from the surface. Morphometric analysis shows that skimming flow is persistent over penitentes, providing conditions conducive for the development of a distinct microclimate within the penitente troughs. For each method a range of ways of defining the representative roughness element height was used, and the calculations were done both with and without application of a zero displacement height offset to account for the likelihood of skimming air flow over the closely spaced penitentes. The computed roughness values are on the order of 0.01–0.10 m during the early part of the ablation season, increasing to 0.10–0.50 m after the end of December, in line with the roughest values previously published for glacier ice. Both the 3-D surface and profile methods of computing roughness are strongly dependent on wind direction. However, the two methods contradict each other in that the maximum roughness computed for the 3-D surface coincides with airflow across the penitente lineation, while maximum roughness computed for sampled profiles coincides with airflow along the penitente lineation. These findings highlight the importance of determining directional roughness and wind direction for strongly aligned surface features and also suggest more work is required to determine appropriate geometrical roughness formulae for linearized features.

Citation: Nicholson, L. I., Pętlicki, M., Partan, B., and MacDonell, S.: 3-D surface properties of glacier penitentes over an ablation season, measured using a Microsoft Xbox Kinect, The Cryosphere, 10, 1897-1913, doi:10.5194/tc-10-1897-2016, 2016.
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Short summary
An Xbox Kinect sensor was used as a close-range surface scanner to produce the first accurate 3D surface models of spikes of snow and ice (known as penitentes) that develop in cold, dry, sunny conditions. The data collected show how penitentes develop over time and how they affect the surface roughness of a glacier. These surface models are useful inputs to modelling studies of how penitentes alter energy exchanges between the atmosphere and the surface and how this affects meltwater production.
An Xbox Kinect sensor was used as a close-range surface scanner to produce the first accurate 3D...
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