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

doi:10.1017/jog.2016.134

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

^*Corresponding author for this work

Bell-Edwards Geographic Data Institute

Research output: Contribution to journal › Article › peer-review

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 language	English
Pages (from-to)	423-435
Number of pages	13
Journal	Journal of Glaciology
Volume	63
Issue number	239
Early online date	16 Jan 2017
DOIs	https://doi.org/10.1017/jog.2016.134
Publication status	Published - Jun 2017

Keywords

Glacier hydrology
Roughness
Subglacial conduits

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10.1017/jog.2016.134Licence: CC BY

Benn_2017_JG_Roughness_CC
© The Author(s) 2017. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 735 KBLicence: CC BY

Raw Kinect data (from "kinect_record") from subglacial conduit under Hansbreen, Svalbard
Mankoff, K. D. (Creator), Gulley, J. D. (Creator), Tulaczyk, S. M. (Creator), Covington, M. D. (Creator), Liu, X. (Creator), Chen, Y. (Creator), Benn, D. I. (Creator) & GŁowacki, P. S. (Creator), Merritt, 1 Oct 2012
http://n2t.net/ark:/13030/m5xk8kq3
Dataset
Gridded conduit floor and roof. Arctic Data Center
Mankoff, K. D. (Creator), Gulley, J. D. (Creator), Tulaczyk, S. M. (Creator), Covington, M. D. (Creator), Liu, X. (Creator), Chen, Y. (Creator), Benn, D. I. (Creator) & GŁowacki, P. S. (Creator), Arctic Data Center, 25 Feb 2016
DOI: 10.18739/A21D2C
Dataset
A 3D model of a conduit under Hansbreen (Hans Glacier), Svalbard. Arctic Data Center.
Mankoff, K. D. (Creator), Gulley, J. D. (Creator), Tulaczyk, S. M. (Creator), Covington, M. D. (Creator), Liu, X. (Creator), Chen, Y. (Creator), Benn, D. I. (Creator) & GŁowacki, P. S. (Creator), Arctic Data Center, 22 Aug 2016
DOI: 10.18739/A20W85
Dataset

Cite this

@article{90c333fa3c424c6099528889b48a12b0,

title = "Roughness of a subglacial conduit under Hansbreen, Svalbard",

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.",

keywords = "Glacier hydrology, Roughness, Subglacial conduits",

author = "Mankoff, {Kenneth D.} and Gulley, {Jason D.} and Tulaczyk, {Slawek M.} and Covington, {Matthew D.} and Xiaofeng Liu and Yunxiang Chen and Benn, {Douglas I.} and G{\L}owacki, {Piotr S.}",

note = "K.M., J.G., X.L. and Y.C. were supported by the National Science Foundation (NSF) under Grant No. #1503928. Thefieldwork team (K.M., J.G., M.C.) were supported by the Norwegian Arctic Research Council and Svalbard Science Forum, RiS #6106. K.M. was also supported by the National Aeronautics and Space Administration (NASA)Headquarters under the NASA Earth and Space Science Fellowship Program – Grant NNX10AN83H, the University of California, Santa Cruz, and the Woods Hole Oceanographic Institution Ocean and Climate Change Institute post-graduate fellowship. Portions of this work were conducted while J.G. was supported by the NSF EAR Postdoctoral Fellowship (#0946767). S.T. was funded by NASA grant NNX11AH61G.",

year = "2017",

month = jun,

doi = "10.1017/jog.2016.134",

language = "English",

volume = "63",

pages = "423--435",

journal = "Journal of Glaciology",

issn = "0022-1430",

publisher = "International Glaciology Society",

number = "239",

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T1 - Roughness of a subglacial conduit under Hansbreen, Svalbard

AU - Mankoff, Kenneth D.

AU - Gulley, Jason D.

AU - Tulaczyk, Slawek M.

AU - Covington, Matthew D.

AU - Liu, Xiaofeng

AU - Chen, Yunxiang

AU - Benn, Douglas I.

AU - GŁowacki, Piotr S.

N1 - K.M., J.G., X.L. and Y.C. were supported by the National Science Foundation (NSF) under Grant No. #1503928. Thefieldwork team (K.M., J.G., M.C.) were supported by the Norwegian Arctic Research Council and Svalbard Science Forum, RiS #6106. K.M. was also supported by the National Aeronautics and Space Administration (NASA)Headquarters under the NASA Earth and Space Science Fellowship Program – Grant NNX10AN83H, the University of California, Santa Cruz, and the Woods Hole Oceanographic Institution Ocean and Climate Change Institute post-graduate fellowship. Portions of this work were conducted while J.G. was supported by the NSF EAR Postdoctoral Fellowship (#0946767). S.T. was funded by NASA grant NNX11AH61G.

PY - 2017/6

Y1 - 2017/6

N2 - 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.

AB - 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.

KW - Glacier hydrology

KW - Roughness

KW - Subglacial conduits

U2 - 10.1017/jog.2016.134

DO - 10.1017/jog.2016.134

M3 - Article

AN - SCOPUS:85019544529

SN - 0022-1430

VL - 63

SP - 423

EP - 435

JO - Journal of Glaciology

JF - Journal of Glaciology

IS - 239

ER -

Roughness of a subglacial conduit under Hansbreen, Svalbard

Abstract

Keywords

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Datasets

Raw Kinect data (from "kinect_record") from subglacial conduit under Hansbreen, Svalbard

Gridded conduit floor and roof. Arctic Data Center

A 3D model of a conduit under Hansbreen (Hans Glacier), Svalbard. Arctic Data Center.

Cite this