Roughness of a subglacial conduit under Hansbreen, Svalbard
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 relat...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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Cambridge University Press
2017-06-01
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| Series: | Journal of Glaciology |
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| Online Access: | https://www.cambridge.org/core/product/identifier/S0022143016001349/type/journal_article |
| _version_ | 1827994473977610240 |
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| author | KENNETH D. MANKOFF JASON D. GULLEY SLAWEK M. TULACZYK MATTHEW D. COVINGTON XIAOFENG LIU YUNXIANG CHEN DOUGLAS I. BENN PIOTR S. GŁOWACKI |
| author_facet | KENNETH D. MANKOFF JASON D. GULLEY SLAWEK M. TULACZYK MATTHEW D. COVINGTON XIAOFENG LIU YUNXIANG CHEN DOUGLAS I. BENN PIOTR S. GŁOWACKI |
| author_sort | KENNETH D. MANKOFF |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-04-10T04:41:30Z |
| format | Article |
| id | doaj.art-23cf24a6f69b419f81975bc091351163 |
| institution | Directory Open Access Journal |
| issn | 0022-1430 1727-5652 |
| language | English |
| last_indexed | 2024-04-10T04:41:30Z |
| publishDate | 2017-06-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Journal of Glaciology |
| spelling | doaj.art-23cf24a6f69b419f81975bc0913511632023-03-09T12:40:23ZengCambridge University PressJournal of Glaciology0022-14301727-56522017-06-016342343510.1017/jog.2016.134Roughness of a subglacial conduit under Hansbreen, SvalbardKENNETH D. MANKOFF0https://orcid.org/0000-0001-5453-2019JASON D. GULLEY1SLAWEK M. TULACZYK2MATTHEW D. COVINGTON3XIAOFENG LIU4YUNXIANG CHEN5DOUGLAS I. BENN6PIOTR S. GŁOWACKI7Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USASchool of Geosciences, University of South Florida, Tampa, FL 33620, USAEarth and Planetary Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, USADepartment of Geosciences, University of Arkansas, 28 Ozark Hall, Fayetteville, AR 72701, USADepartment of Civil and Environmental Engineering, Pennsylvania State University, University Park, PA 16802, USADepartment of Civil and Environmental Engineering, Pennsylvania State University, University Park, PA 16802, USASchool of Geography and Geosciences, University of St Andrews, North St, St Andrews KY16 9AL, UKInstitute of Geophysics, Polish Academy of Sciences, ul. Księcia, Janusza 64, 01-452 Warszawa, PolskaHydraulic 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.https://www.cambridge.org/core/product/identifier/S0022143016001349/type/journal_articleglacier hydrologyroughnesssubglacial conduits |
| spellingShingle | KENNETH D. MANKOFF JASON D. GULLEY SLAWEK M. TULACZYK MATTHEW D. COVINGTON XIAOFENG LIU YUNXIANG CHEN DOUGLAS I. BENN PIOTR S. GŁOWACKI Roughness of a subglacial conduit under Hansbreen, Svalbard Journal of Glaciology glacier hydrology roughness subglacial conduits |
| title | Roughness of a subglacial conduit under Hansbreen, Svalbard |
| title_full | Roughness of a subglacial conduit under Hansbreen, Svalbard |
| title_fullStr | Roughness of a subglacial conduit under Hansbreen, Svalbard |
| title_full_unstemmed | Roughness of a subglacial conduit under Hansbreen, Svalbard |
| title_short | Roughness of a subglacial conduit under Hansbreen, Svalbard |
| title_sort | roughness of a subglacial conduit under hansbreen svalbard |
| topic | glacier hydrology roughness subglacial conduits |
| url | https://www.cambridge.org/core/product/identifier/S0022143016001349/type/journal_article |
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