C22B-01
Surface Roughness and Snow Accumulation in East Antarctica
Tuesday, 15 December 2015: 10:20
3007 (Moscone West)
Ted A Scambos1, Patricia Linda Vornberger2, Jennifer A Bohlander3, Indrani Das4, Marin Klinger5, Allen Pope5, Jan Lenaerts6 and Mark A Fahnestock7, (1)National Snow and Ice Data Center, CIRES University of Colorado, Boulder, CO, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)Polar Science Consulting, Cary, NC, United States, (4)Lamont -Doherty Earth Observatory, Palisades, NY, United States, (5)National Snow and Ice Data Center, Boulder, CO, United States, (6)Utrecht University, Utrecht, Netherlands, (7)University of Alaska Fairbanks, Fairbanks, AK, United States
Abstract:
A complex relationship exists between snow accumulation (e.g., net surface mass balance) and meter-scale surface roughness as represented by sastrugi and erosional structures over the East Antarctic Ice Sheet (EAIS). The morphology of the ice sheet at this scale is a result of a complex interaction between katabatic winds, synoptic storms, and the slope of the surface, all driving local patterns of snow accretion and sublimation. In megadune regions, the accumulation, surface slope, and surface roughness are highly correlated with slope. Smooth glazed surfaces are present on the steeper leeward wind-faces, and much rougher snow-accreting megadunes are present on the windward (depositional) slope. However, the highest elevation areas near the ridge crest of the EAIS (above ~3200 m) have a converse relationship between roughness and accumulation. Here, very low wind ridge crest areas are smooth and have higher accumulation than adjacent, slightly steeper regions that exhibit a slight increase in roughness. Below the main regions of megadunes (<~2000 m) wind glaze areas gradually become rougher as wind scouring and erosion dominate locally steeper regions. In coastal areas (<~1000), roughness is highly variable, and is tied to frequent synoptic storm deposition. We compare roughness data derived from MISR (Multi-angle Imaging SpectroRadiometer) and Landsat 8 acquisitions with available wind and accumulation data from climate model results and field measurements. Roughness is determined by sunlight scattering relative to viewing geometry (MISR) or from the amplitude of textural characteristics tied to surface sastrugi (Landsat 8). Both are validated by comparison with meter-scale images (WorldView-1) and field observations. MISR roughness mapping shows persistent qualitative patterns of surface roughness across the EAIS, but an absolute roughness scale mapping is difficult to generate because of complex viewing, illumination, and bi-directional reflectance variations of the snow surface. Landsat 8 band 8 provides a more constrained viewing geometry (nadir, sun-synchronous observations) and has a high radiometric sensitivity and adequate resolution (15 m) to reveal textural details in a consistent and quantitative way.
