HR: 1330h
AN: C32A-0421    [PDF]
TI: ICESat/GLAS measurement of Ice sheet surface slope and roughness
AU: * Yi, D
EM: donghui@icesat2.gsfc.nasa.gov
AF: Raytheon ITSS NASA/GSFC, Code 971, Ocean and Ice Branch, Goddard Space Flight Center, Greenbelt, MD 20771
AU: Zwally, H J
EM: zwally@icesat2.gsfc.nasa.gov
AF: NASA/GSFC, Code 971, Ocean and Ice Branch, Goddard Space Flight Center, Greenbelt, MD 20771
AB: Surface slope and roughness are important features of ice sheets that are affected by bedrock topography, ice flow, ice thickness, and wind. Return-pulse waveforms from ICESat/GLAS provide surface elevations and information on surface slope and roughness. Surface slope and roughness within the laser footprint both affect the spread of return waveform, so information on surface slope and roughness can be derived by comparing the transmitted and return pulse waveforms. The shape of the transmitted waveform is nearly Gaussian. For typical ice sheet surfaces, the return pulse shape is also very close to Gaussian. By fitting Gaussian functions to the transmitted and return pulse waveforms and calculating the increase in width of the return pulse, surface roughness can be calculated if the surface slope is known, or vice versa. The ICESat/GLAS 1064 nm laser footprint diameter is about 70 meters and the footprint separation is about 170 meters. The small-scale surface roughness derived from the pulse shape is mostly due to wind-driven surface sastrugi. Over the larger ice sheet slopes, the pulse shape is dominated mainly by the surface slope. Information on the larger-scale (larger than 170 m) surface slope and surface undulations is also derived from successive along-track ICESat/GLAS elevations. The ICESat orbit covers Antarctica to 86$\deg$S and all of the Greenland ice sheet. Spatial distributions of surface roughness and slopes over the ice sheets for the period of ICESat operation are described. Effects of partial detector/amplifier saturation on the return pulse shape and the calculated roughness and slopes are also discussed.
DE: 1640 Remote sensing
DE: 1827 Glaciology (1863)
DE: 1894 Instruments and techniques
DE: 4560 Surface waves and tides (1255)
SC: Cryosphere [C]
MN: 2003 Fall Meeting