HR: 10:55h
AN: C12B-03    [Abstracts]
TI: Analysis of Surface Roughness Derived from Airborne Laser Altimetry on the Greenland Ice Sheet and Comparison with Stratigraphic Records
AU: * van der Veen, C J
EM: vanderveen.1@osu.edu
AF: Department of Geological Sciences and BPRC The Ohio State University, 125 South Oval Mall , Columbus, OH 43210 United States
AU: Csatho, B
EM: csatho.1@osu.edu
AF: Byrd Polar Research Center, OSU, 1090 Carmack Rd., Columbus, OH 43210 United States
AU: Ahn, Y
EM: ahn.74@osu.edu
AF: Byrd Polar Research Center, OSU, 1090 Carmack Rd., Columbus, OH 43210 United States
AU: Krabill, W
EM: krabill@osb1.nasa.gov
AF: Laboratory of Hydrospheric Processes, NASA/GSFC, NASA WFF, Bldg-159 , Wallops Island, VA 23337 United States
AU: Mosley-Thompson, E
EM: thompson.4@osu.edu
AF: Department of Geography, OSU, 154 North Oval Mall, Columbus, OH 43210 United States
AB: While repeat satellite altimetry and volume balance studies indicate that the central parts of the Greenland Ice Sheet is in balance, repeat airborne laser altimetry have revealed significant thinning of the ice sheet at lower elevations, enough to raise sea level by about 0.15 mm/yr. A major impediment for assessing the long-term significance of observed changes is the relatively short record of observations currently available. Over time intervals of a few years, the elevation of the ice surface responds to interannual fluctuations in snowfall which may lead to apparent thickening or thinning trends that are not sustained over longer time periods. Since 1995, a suite of shallow to intermediate depth cores has been collected in Greenland by NASA's Program for Arctic Regional Climate Assessment (PARCA) to support the efforts to establish the mass balance of the ice sheet. One major difficulty in extracting inter-annual variability from these cores is to estimate the contribution of small-scale spatial variability influenced by surface roughness such as sastrugi. Previously we demonstrated the use of airborne laser profiling for estimating surface roughness in Greenland's Summit region. Now we extend this analysis to other parts of the Greenland ice sheet. High resolution surface elevation data were collected by NASA's Airborne Topographic Mapper around several ice core sites in 1995. To compute the surface roughness, first the large-scale slope is removed by piecewise fitting of linear segments using least-squares method. Then the surface roughness is computed as the standard deviation of the elevation fluctuations for flight segments of predetermined length. To obtain the estimated variance of interannual variability, the variance of the surface effects (roughness) was subtracted from the total variance of the ice core records. We also analyzed the spatial coherence of surface irregularities by computing correlation functions and variograms. Where differently-oriented flight lines were available, spatial anisotropy was also investigated. As we demonstrate, the spatial coherence obtained from the high resolution topography provides important information on the optimum spacing of multiple cores.
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 1620 Climate dynamics (3309)
DE: 1640 Remote sensing
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting