HR: 11:10h
AN: C12B-04    [Abstracts]
TI: Determination of Snow and Ice Surface Roughness and its Importance for Ablation
AU: * Herzfeld, U C
EM: herzfeld@iceberg.colorado.edu
AF: CIRES, University of Colorado Boulder, Boulder, CO 80309-0449 United States
AU: Box, J
EM: jason.box@osu.edu
AF: Byrd Polar Research Center, Ohio State University, Columbus, OH 99999 United States
AU: Steffen, K
EM: koni@seaice.colorado.edu
AF: CIRES, University of Colorado Boulder, Boulder, CO 80309-0449 United States
AU: Mayer, H
EM: mayerh@tryfan.colorado.edu
AF: Institut f. Mechanik Institut f. Mechanik, Technische Universitaet Darmstadt, Darmstadt, 64289 Germany
AU: Caine, N
EM: cainen@spot.colorado.edu
AF: INSTAAR, University of Colorado Boulder, Boulder, CO 80309-0450 United States
AU: Losleben, M
EM: markl@culter.colorado.edu
AF: INSTAAR, University of Colorado Boulder, Boulder, CO 80309-0450 United States
AB: Study of the surface roughness of snow fields, glaciers, and ice sheets requires measurement and analysis of the surface's three-dimensional features, anisotropies, and complex microtopography. Observing that the notions of relief and surface roughness differ only with respect to scale, we consider surface roughness a spatial variable defined as the derivative of (micro)topography. Spatial snow and ice surface roughness can be measured with the Glacier Roughness Sensor, a multichannel instrument that collects data at 0.2~m across-track, 0.1~m along-track resolution and subcentimeter vertical accuracy, with differential kinematic GPS data for positioning. Roughness data are analysed using the geostatistical classification method. Results of the classification provide (1) information on the morphogenesis of snow or ice surface types of a given environment, (2) subscale information for the interpretation of satellite data and facilitate (3) segmentation of a study area into characteristic surface classes. One application is monitoring the extent of ablation in the Greenland Ice Sheet. By deriving a mathematical relationship between aerodynamic roughness length and spatial surface roughness, calculating roughness from actual observations and driving energy balance models with the range of resultant values and micro-meteorological data, it could be shown that melt energy varies with a factor of two dependent on surface roughness. Hence surface roughness is an important geophysical variable that needs to be considered in any scenario of a warming ice sheet.
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting