Roughness of a subglacial conduit under Hansbreen, Svalbard

Kenneth D. Mankoff, Jason D. Gulley, Slawek M. Tulaczyk, Matthew D. Covington, Xiaofeng Liu, Yunxiang Chen, Douglas I. Benn, Piotr S. GŁowacki

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Hydraulic roughness exerts an important but poorly understood control on water pressure in subglacial conduits. Where relative roughness values are <5%, hydraulic roughness can be related to relative roughness using empirically-derived equations such as the Colebrook-White equation. General relationships between hydraulic roughness and relative roughness do not exist for relative roughness >5%. Here we report the first quantitative assessment of roughness heights and hydraulic diameters in a subglacial conduit. We measured roughness heights in a 125 m long section of a subglacial conduit using structure-from-motion to produce a digital surface model, and hand-measurements of the b-axis of rocks. We found roughness heights from 0.07 to 0.22 m and cross-sectional areas of 1-2 m2, resulting in relative roughness of 3-12% and >5% for most locations. A simple geometric model of varying conduit diameter shows that when the conduit is small relative roughness is >30% and has large variability. Our results suggest that parameterizations of conduit hydraulic roughness in subglacial hydrological models will remain challenging until hydraulic diameters exceed roughness heights by a factor of 20, or the conduit radius is >1 m for the roughness elements observed here.

Original languageEnglish (US)
Pages (from-to)423-435
Number of pages13
JournalJournal of Glaciology
Volume63
Issue number239
DOIs
StatePublished - Jun 1 2017

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roughness
hydraulics
parameterization
rock

All Science Journal Classification (ASJC) codes

  • Earth-Surface Processes

Cite this

Mankoff, K. D., Gulley, J. D., Tulaczyk, S. M., Covington, M. D., Liu, X., Chen, Y., ... GŁowacki, P. S. (2017). Roughness of a subglacial conduit under Hansbreen, Svalbard. Journal of Glaciology, 63(239), 423-435. https://doi.org/10.1017/jog.2016.134
Mankoff, Kenneth D. ; Gulley, Jason D. ; Tulaczyk, Slawek M. ; Covington, Matthew D. ; Liu, Xiaofeng ; Chen, Yunxiang ; Benn, Douglas I. ; GŁowacki, Piotr S. / Roughness of a subglacial conduit under Hansbreen, Svalbard. In: Journal of Glaciology. 2017 ; Vol. 63, No. 239. pp. 423-435.
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Mankoff, KD, Gulley, JD, Tulaczyk, SM, Covington, MD, Liu, X, Chen, Y, Benn, DI & GŁowacki, PS 2017, 'Roughness of a subglacial conduit under Hansbreen, Svalbard', Journal of Glaciology, vol. 63, no. 239, pp. 423-435. https://doi.org/10.1017/jog.2016.134

Roughness of a subglacial conduit under Hansbreen, Svalbard. / Mankoff, Kenneth D.; Gulley, Jason D.; Tulaczyk, Slawek M.; Covington, Matthew D.; Liu, Xiaofeng; Chen, Yunxiang; Benn, Douglas I.; GŁowacki, Piotr S.

In: Journal of Glaciology, Vol. 63, No. 239, 01.06.2017, p. 423-435.

Research output: Contribution to journalArticle

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Mankoff KD, Gulley JD, Tulaczyk SM, Covington MD, Liu X, Chen Y et al. Roughness of a subglacial conduit under Hansbreen, Svalbard. Journal of Glaciology. 2017 Jun 1;63(239):423-435. https://doi.org/10.1017/jog.2016.134