Ice-flow characteristics over a rough bedrock: implications for ice-core interpretation

• Main Author: Frank Pattyn
• Format: Report
• Language: English
• Published: Department of Geography, Vrije Universiteit Brussel 2002
• Subjects: Dronning Maud Land; Antarc*; Antarctica; EPICA; ice core; Ice Sheet; Polar meteorology and glaciology
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2945; http://id.nii.ac.jp/1291/00002945/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2945&item_no=1&attribute_id=18&file_no=1

Recent observations in western Dronning Maud Land, Antarctica, point to a relatively high bedrock roughness in the area of the future EPICA drilling site. It is commonly accepted that such a roughness does not favor the interpretation of deep ice cores as basal ice-sheet interactions might disturb the bottom ice layers. The present study aims at examining the ice-flow characteristics over a strongly undulating bed and investigates its influence on age-depth profiles in the ice sheet.For this purpose a high-resolution time-dependent two-dimensional flowline model was developed (horizontal gridsize ≦ 1km), taking into account all relevant stresses at such a small scale. The model is solved on a fixed finite-difference grid, and compared with a similar model, solving the velocity field according to the shallow-ice approximation. The analysis is presented for sinusoidal bedrock undulations with amplitude-to-wavelength ratio comparable to those observed by radio-echo sounding (D.Steinhage et al., Ann. Glaciol., 29, 267, 1999). Calculations are performed over a period of 300 ka. Results demonstrate that the influence of a high bed roughness on the age-depth profiles is not only confined close to the bed, but near the surface as well, which might affect the interpretation of shallow ice cores.