Preprints
https://doi.org/10.5194/egusphere-2022-1220
https://doi.org/10.5194/egusphere-2022-1220
 
28 Nov 2022
28 Nov 2022
Status: this preprint is open for discussion.

Differential impact of isolated topographic bumps on glacial ice flow and subglacial processes

Marion A. McKenzie1, Lauren M. Simkins1, Jacob S. Slawson1,a, Emma J. MacKie2, and Shujie Wang3 Marion A. McKenzie et al.
  • 1Department of Environmental Sciences, University of Virginia, 291 McCormick Rd., Charlottesville, VA 22904
  • 2Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, PL 32611-2120
  • 3Department of Geography, Pennsylvania State University, 302 N Burrowes St., University Park, PA 16802
  • aCurrent affiliation: Department of geology and Geological Engineering, Colorado School of Mines, 1516 Illinois St., Golden, CO 80401

Abstract. Topographic highs (“bumps”) across glaciated landscapes have the potential to temporarily slow glacial ice flow or, conversely, increase ice flow through strain heating and subglacial meltwater production. Isolated bumps of variable size across the deglaciated landscape of the Cordilleran Ice Sheet (CIS) of Washington state present an opportunity to assess the influence of topographic highs on ice-bed interactions and ice flow organization. This work utilizes semi-automatic mapping techniques of subglacial bedforms to characterize the morphology of streamlined subglacial bedforms including elongation, surface relief, and orientation – all of which provide insight into subglacial processes during post-Last Glacial Maximum deglaciation of the landscape. We identify a bump-size threshold of ~ 4.5 km3 in which bumps larger than this size will consistently and significantly disrupt both ice-flow organization and subglacial sedimentary processes – fundamental to the genesis of streamlined subglacial bedforms. Additionally, sedimentary processes are most mature downstream of bumps as reflected by enhanced bedform elongation and reduced surface relief, likely due to increased availability and production of subglacial sediment and meltwater. While isolated topography is found to play a role in disrupting ice flow, not all bumps have the same degree of impact. The variable influence of isolated topographic bumps on ice flow in this system has significance for outlet glaciers of the Greenland Ice Sheet (GrIS) due to general topographic similarities.

Marion A. McKenzie et al.

Status: open (extended)

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  • RC1: 'Comment on egusphere-2022-1220', Anna L.C. Hughes, 23 Jan 2023 reply

Marion A. McKenzie et al.

Data sets

Streamlined subglacial bedforms across isolated topographic highs in the Puget Lowland, Washington state McKenzie, M. A., Simkins, L. M., Slawson, J. S., and Wang, S. https://issues.pangaea.de/browse/PDI-33324

Marion A. McKenzie et al.

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Short summary
Topographic highs (“bumps”) across glaciated landscapes have the potential to affect glacial ice. Topographic bumps in the deglaciated Puget Lowland are assessed for streamlined glacial features to provide insight on ice-bed interactions. We identify a threshold in which bumps will consistently and significantly disrupt and sedimentary processes in this location. However, not all bumps have the same degree of impact. The system assessed here has relevance to parts of the Greenland Ice Sheet.