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Start Over Author "Hubbard, Bryn" Publisher american geophysical union (agu)
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2. Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier

Author

Hubbard, Bryn, Christoffersen, Poul, Doyle, Samuel H, Chudley, Thomas R, Schoonman, Charlotte M, Law, Robert, Bougamont, Marion, Christoffersen, Poul [0000-0003-2643-8724], Law, Robert [0000-0003-0067-5537], Bougamont, Marion [0000-0001-7196-4171], and Apollo - University of Cambridge Repository

Subjects
deep crevasse, glacier, Greenland Ice Sheet, optical televiewer, borehole, crevasse
Abstract

Funder: Aberystwyth University Capital Equipment Fund, Optical televiewer borehole logging within a crevassed region of fast‐moving Store Glacier, Greenland, revealed the presence of 35 high‐angle planes that cut across the background primary stratification. These planes were composed of a bubble‐free layer of refrozen ice, most of which hosted thin laminae of bubble‐rich “last frozen” ice, consistent with the planes being the traces of former open crevasses. Several such last‐frozen laminae were observed in four traces, suggesting multiple episodes of crevasse reactivation. The frequency of crevasse traces generally decreased with depth, with the deepest detectable trace being 265 m below the surface. This is consistent with the extent of the warmer‐than‐modeled englacial ice layer in the area, which extends from the surface to a depth of ∼400 m. Crevasse trace orientation was strongly clustered around a dip of 63° and a strike that was offset by 71° from orthogonal to the local direction of principal extending strain. The traces’ antecedent crevasses were therefore interpreted to have originated upglacier, probably ∼8 km distant involving mixed‐mode (I and III) formation. We conclude that deep crevassing is pervasive across Store Glacier, and therefore also at all dynamically similar outlet glaciers. Once healed, their traces represent planes of weakness subject to reactivation during subsequent advection through the glacier. Given their depth, it is highly likely that such traces—particularly those formed downglacier—survive surface ablation to reach the glacier terminus, where they may represent foci for fracture and iceberg calving.

Published
2021
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6. Thank You to Our 2018 Peer Reviewers

Author

East, Amy E., primary, Buffington, John, additional, Coco, Giovanni, additional, Finnegan, Noah J., additional, Hoitink, Ton A. J. F., additional, and Hubbard, Bryn, additional

Published
2019
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11. Earth and Space Science for the Benefit of Humanity

Author

Hanson, Brooks, primary, Lunn, Jenny, additional, van der Pluijm, Ben, additional, Orcutt, John, additional, Colwell, Rita, additional, Trumbore, Susan, additional, Becker, Thorsten, additional, Diffenbaugh, Noah, additional, Pincus, Robert, additional, Liemohn, Mike, additional, ten Brink, Uri, additional, Brewer, Peter, additional, Zhang, Minghua, additional, Hauck II, Steven, additional, Hubbard, Bryn, additional, Goni, Miguel, additional, Thomas, Ellen, additional, Wilkinson, Phil, additional, Moldwin, Mark, additional, Knipp, Delores, additional, Geissman, John, additional, and Clark, Martyn, additional

Published
2017
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