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Subseasonal changes observed in subglacial channel pressure, size, and sediment transport

Gimbert, Florent and Tsai, Victor C. and Amundson, Jason M. and Bartholomaus, Timothy C. and Walter, Jacob I. (2016) Subseasonal changes observed in subglacial channel pressure, size, and sediment transport. Geophysical Research Letters, 43 (8). pp. 3786-3794. ISSN 0094-8276. doi:10.1002/2016GL068337.

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Water that pressurizes the base of glaciers and ice sheets enhances glacier velocities and modulates glacial erosion. Predicting ice flow and erosion therefore requires knowledge of subglacial channel evolution, which remains observationally limited. Here we demonstrate that detailed analysis of seismic ground motion caused by subglacial water flow at Mendenhall Glacier (Alaska) allows for continuous measurement of daily to subseasonal changes in basal water pressure gradient, channel size, and sediment transport. We observe intermittent subglacial water pressure gradient changes during the melt season, at odds with common assumptions of slowly varying, low-pressure channels. These observations indicate that changes in channel size do not keep pace with changes in discharge. This behavior strongly affects glacier dynamics and subglacial channel erosion at Mendenhall Glacier, where episodic periods of high water pressure gradients enhance glacier surface velocity and channel sediment transport by up to 30% and 50%, respectively. We expect the application of this framework to future seismic observations acquired at glaciers worldwide to improve our understanding of subglacial processes.

Item Type:Article
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URLURL TypeDescription
Gimbert, Florent0000-0001-7350-3563
Tsai, Victor C.0000-0003-1809-6672
Walter, Jacob I.0000-0001-7127-9422
Additional Information:© 2016 American Geophysical Union. Received 8 DEC 2015; Accepted 5 APR 2016; Accepted article online 7 APR 2016; Published online 21 APR 2016. This study was funded by NSF grant EAR-1453263. We thank Flavien Beaud and an anonymous reviewer for thorough reviews that improved the manuscript. We also thank Michael Lamb, Olivier Gagliardini, Jean-Philippe Avouac, Gael Durand and Adrien Gilbert for fruitful discussions.
Group:Seismological Laboratory
Funding AgencyGrant Number
Issue or Number:8
Record Number:CaltechAUTHORS:20160715-111120593
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Official Citation:Gimbert, F., V. C. Tsai, J. M. Amundson, T. C. Bartholomaus, and J. I. Walter (2016), Subseasonal changes observed in subglacial channel pressure, size, and sediment transport, Geophys. Res. Lett., 43, 3786–3794, doi:10.1002/2016GL068337
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69059
Deposited By: Tony Diaz
Deposited On:27 Jul 2016 20:59
Last Modified:11 Nov 2021 04:08

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