Subglacial Conduit Roughness: Insights From Computational Fluid Dynamics Models

• Published in: Geophysical Research Letters
• Main Authors: Chen, Yunxiang, Liu, Xiaofeng, Gulley, Jason D., Mankoff, Kenneth D.
• Format: Text
• Language: unknown
• Published: Digital Commons @ University of South Florida 2018
• Subjects: Subglacial Conduit Roughness; Insight; Computational Fluid Dynamics Models; Svalbard; Norway; Hansbreen; glacier
• Online Access: https://digitalcommons.usf.edu/kip_articles/5258; https://doi.org/10.1029/2018GL079590

Flow resistance in subglacial conduits regulates the basal water pressure and sliding speeds of glaciers by controlling drainage efficiency and conduit enlargement and closure. Flow dynamics within subglacial conduits, however, remain poorly understood due to limited accessibility. Here we report the results of the first computational fluid dynamics simulations of flow within a realistic subglacial conduit beneath Hansbreen, a polythermal glacier in Svalbard, Norway. The simulated friction factor is 2.34 ± 0.05, which is around 5 to 230 times greater than values (0.01–0.5) commonly used in glacier hydrological modeling studies. Head losses from sinuosity and cross‐sectional variations dominate flow resistance (∼ 94%), whereas surface roughness from rocks and ice features contributes only a small portion (∼6%). Most glacier hydrology models neglect head losses due to sinuosity and cross‐sectional variations and thus severely underestimate flow resistance, overestimating the conduit peak effective pressure by 2 times and underestimating the conduit enlargement area by 3.4 times, respectively.