Subglacial bedform sensitivity to bed characteristics across the deglaciated Northern Hemisphere

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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 ice 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 erosional and depositional bedforms, created during and following the Last Glacial Maximum, across nine geologic 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 systematically provides a constraint on landform elongation during genesis and minimum morphometrics needed to resolve such bedforms in remote sensing data. Distribution ranges of bedform elongations are remarkably similar across all sites regardless of bed characteristics. These similarities in bedform metrics regardless of bed properties indicate all bed types may support streaming ice conditions. Regionally-constrained topography and easily erodible beds host the most elongate bedforms yet the widest range in bedform elongation and surface relief. This suggests higher ice-flow velocities and continuity of flow paths despite spatially heterogeneous landform-generating processes. In contrast, regions with unconstrained topography and lithified sedimentary beds contain high conformity in bedform density, relief, and elongation, indicating more spatially homogeneous interactions at the ice-bed interface and consistency in ice-flow velocity. Regardless of whether bedforms are erosional or depositional products, we ultimately find a relatively higher sensitivity of bedform elongation (i.e., ice streaming speed) to regional topography while bedform density is more sensitive to bed lithology. The findings presented here should be extrapolated to interpret processes of subglacial erosion and deposition, ice-bed interactions, and streaming 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 23:06

Last Updated: 2021-11-11 07:06

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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