Aerodynamic roughness of glacial ice surfaces derived from high‐resolution topographic data

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• 作者：Mark W. Smith ; Duncan J. Quincey ; Timothy Dixon ; Robert G. Bingham ; Jonathan L. Carrivick ; Tristram D. L. Irvine‐Fynn ; David M. Rippin
• 刊名：Journal of Geophysical Research: Earth Surface
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：121
• 期：4
• 页码：748-766
• 全文大小：5.4MB
• ISSN：2169-9011

文摘

This paper presents new methods of estimating the aerodynamic roughness (z₀) of glacier ice directly from three-dimensional point clouds and digital elevation models (DEMs), examines temporal variability of z₀, and presents the first fully distributed map of z₀ estimates across the ablation zone of an Arctic glacier. The aerodynamic roughness of glacier ice surfaces is an important component of energy balance models and meltwater runoff estimates through its influence on turbulent fluxes of latent and sensible heat. In a warming climate these fluxes are predicted to become more significant in contributing to overall melt volumes. Ice z₀ is commonly estimated from measurements of ice surface microtopography, typically from topographic profiles taken perpendicular to the prevailing wind direction. Recent advances in surveying permit rapid acquisition of high-resolution topographic data allowing revision of assumptions underlying conventional z₀ measurement. Using Structure from Motion (SfM) photogrammetry with Multi-View Stereo (MVS) to survey ice surfaces with millimeter-scale accuracy, z₀ variation over 3 orders of magnitude was observed. Different surface types demonstrated different temporal trajectories in z₀ through 3 days of intense melt. A glacier-scale 2 m resolution DEM was obtained through terrestrial laser scanning (TLS), and subgrid roughness was significantly related to plot-scale z₀. Thus, we show for the first time that glacier-scale TLS or SfM-MVS surveys can characterize z₀ variability over a glacier surface potentially leading to distributed representations of z₀ in surface energy balance models.