Flow and structure in a dendritic glacier with bedrock steps

• Published in: Journal of Glaciology
• Main Authors: HESTER JISKOOT, THOMAS A FOX, WESLEY VAN WYCHEN
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2017
• Subjects: glacier flow; glacier erosion; glacier surges; mountain glaciers; structural glaciology; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Shackleton; Shackleton Glacier; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2017.58; https://doaj.org/article/27854bb79c7242edbe499614c546d090

We analyse ice flow and structural glaciology of Shackleton Glacier, a dendritic glacier with multiple icefalls in the Canadian Rockies. A major tributary-trunk junction allows us to investigate the potential of tributaries to alter trunk flow and structure, and the formation of bedrock steps at confluences. Multi-year velocity-stake data and structural glaciology up-glacier from the junction were assimilated with glacier-wide velocity derived from Radarsat-2 speckle tracking. Maximum flow speeds are 65 m a−1 in the trunk and 175 m a−1 in icefalls. Field and remote-sensing velocities are in good agreement, except where velocity gradients are high. Although compression occurs in the trunk up-glacier of the tributary entrance, glacier flux is steady state because flow speed increases at the junction due to the funnelling of trunk ice towards an icefall related to a bedrock step. Drawing on a published erosion model, we relate the heights of the step and the hanging valley to the relative fluxes of the tributary and trunk. It is the first time that an extant glacier is used to test and support such model. Our study elucidates the inherent complexity of tributary/trunk interactions and provides a conceptual model for trunk flow restriction by a tributary in surge-type glaciers.