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Excavation of subglacial bedrock channels by seasonal meltwater flow

Beaud, Flavien and Venditti, Jeremy G. and Flowers, Gwenn E. and Koppes, Michele (2018) Excavation of subglacial bedrock channels by seasonal meltwater flow. Earth Surface Processes and Landforms, 43 (9). pp. 1960-1972. ISSN 0197-9337. https://resolver.caltech.edu/CaltechAUTHORS:20180726-110720855

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Abstract

Subglacial water flow drives the excavation of a variety of bedrock channels including tunnel valleys and inner gorges. Subglacial floods of various magnitudes – events occurring once per year or less frequently with discharges larger than a few hundred cubic metres per second – are often invoked to explain the erosive power of subglacial water flow. In this study we examine whether subglacial floods are necessary to carve bedrock channels, or if more frequent melt season events (e.g. daily production of meltwater) can explain the formation of substantial bedrock channels over a glacial cycle. We use a one‐dimensional numerical model of bedrock erosion by subglacial meltwater, where water flows through interacting distributed and channelized drainage systems. The shear stresses produced drive bedrock erosion by bed‐ and suspended‐load abrasion. We show that seasonal meltwater discharge can incise an incipient bedrock channel a few tens of centimetres deep and several metres wide, assuming abrasion is the only mechanism of erosion, a particle size of D=256 mm and a prescribed sediment supply per unit width. Using the same sediment characteristics, flood flows yield wider but significantly shallower bedrock channels than seasonal meltwater flows. Furthermore, the smaller the shear stresses produced by a flood, the deeper the bedrock channel. Shear stresses produced by seasonal meltwater are sufficient to readily transport boulders as bedload. Larger flows produce greater shear stresses and the sediment is carried in suspension, which produces fewer contacts with the bed and less erosion. We demonstrate that seasonal meltwater discharge can excavate bedrock volumes commensurate with channels several tens of metres to a few hundred metres wide and several tens of metres deep over several thousand years. Such simulated channels are commensurate with published observations of tunnel valleys and inner gorges.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/esp.4367DOIArticle
ORCID:
AuthorORCID
Beaud, Flavien0000-0002-0687-8741
Venditti, Jeremy G.0000-0002-2876-4251
Flowers, Gwenn E.0000-0002-3574-9324
Additional Information:© 2018 John Wiley & Sons, Ltd. Issue Online: 08 July 2018; Version of Record online: 16 April 2018; Accepted manuscript online: 20 February 2018; Manuscript accepted: 08 February 2018; Manuscript revised: 05 February 2018; Manuscript received: 22 September 2017. Funding: Swiss National Cooperative for the Disposal of Radioactive Waste (Nagra); Natural Sciences and Engineering Research Council.
Funders:
Funding AgencyGrant Number
Swiss National Cooperative for the Disposal of Radioactive WasteUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords:glacial erosion; subglacial hydrology; subglacial meltwater erosion; tunnel valley; inner gorge
Issue or Number:9
Record Number:CaltechAUTHORS:20180726-110720855
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180726-110720855
Official Citation:Beaud, F., Venditti, J. G., Flowers, G. E., and Koppes, M. (2018) Excavation of subglacial bedrock channels by seasonal meltwater flow. Earth Surf. Process. Landforms, 43: 1960–1972. https://doi.org/10.1002/esp.4367
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88299
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:26 Jul 2018 18:13
Last Modified:03 Oct 2019 20:05

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