Streamlined subglacial bedform sensitivity to bed characteristics across the deglaciated Northern Hemisphere

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1002/esp.5382. This is version 2 of this Preprint.

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Authors

Marion A. McKenzie , Lauren Miller Simkins , Sarah Principato

Abstract

Streamlined subglacial bedforms observed in deglaciated landscapes provide the opportunity to assess the sensitivity of glacier dynamics to bed characteristics across broader spatiotemporal scales than is possible for contemporary glacial systems. While many studies of streamlined subglacial bedforms rely on manual mapping and qualitative (i.e., visual) assessment, we semi-automatically identify 11,628 sedimentary and bedrock bedforms, created during and following the Last Glacial Maximum across nine geologically and topographically diverse deglaciated sites in the Northern Hemisphere. Using this large dataset of landforms and associated morphometrics, we empirically test the importance of subglacial terrain on bedform morphology and ice-flow behavior. A minimum bedform length–width ratio threshold provides a constraint on minimum morphometrics needed for streamlined bedforms to develop. Similarities in bedform metric distribution regardless of bed properties indicate that all bed types may support similar distributions of warm-based ice flow conditions. Ice flow within valleys with easily erodible beds host the most elongate bedforms yet the widest range in bedform elongation and bedform surface relief. The presence of these highly elongate bedforms suggest high ice-flow velocities occur within valley settings despite spatially heterogeneous landform-generating processes. In contrast, lithified sedimentary beds within regions not constrained by topography on the scale of 1–102 km contain bedforms with high density and packing, low change in surface relief and low elongation, indicating spatially uniform and organized interactions at the ice–bed interface and consistency in ice-flow velocity. Regardless of genesis, we find a sensitivity of bedform elongation (i.e., used to interpret ice-flow speed or persistence) to topographic conditions on the scale of 1–102 km, while bedform density is sensitive to bed lithology. The findings presented in this study provide analogues for processes of subglacial erosion and deposition, ice–bed interactions and warm-based ice flow within contemporary glacial systems.

DOI

https://doi.org/10.31223/X5Z037

Subjects

Earth Sciences, Geology, Geomorphology, Glaciology

Keywords

geomorphology, glacial landforms, ice flow, topography, lithology, ice sheet, glacial landforms, ice flow, Topography, lithology, ice sheet

Dates

Published: 2021-11-10 09:06

Last Updated: 2022-05-05 18:47

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License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
The authors have no conflict of interest to report.

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