Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution
Hydraulic roughness accounts for energy dissipated as heat and should exert an important control on rates of subglacial conduit enlargement by melting. Few studies, however, have quantified how subglacial conduit roughness evolves over time or how that evolution affects models of conduit enlargement...
Published in: | Earth Surface Processes and Landforms |
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2014
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ftmichigantuniv:oai:digitalcommons.mtu.edu:michigantech-p-22921 2023-05-15T16:22:18+02:00 Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution Gulley, J. D. Spellman, P. Covington, M. D. Martin, J. B. Benn, D. I. Catania, G. 2014-03-15T07:00:00Z https://digitalcommons.mtu.edu/michigantech-p/3619 https://doi.org/10.1002/esp.3447 unknown Digital Commons @ Michigan Tech https://digitalcommons.mtu.edu/michigantech-p/3619 https://doi.org/10.1002/esp.3447 Michigan Tech Publications Englacial Friction factor Glacier hydrology Roughness Subglacial Department of Geological and Mining Engineering and Sciences Department of Civil Environmental and Geospatial Engineering Civil and Environmental Engineering Geological Engineering Mining Engineering text 2014 ftmichigantuniv https://doi.org/10.1002/esp.3447 2022-01-23T10:55:03Z Hydraulic roughness accounts for energy dissipated as heat and should exert an important control on rates of subglacial conduit enlargement by melting. Few studies, however, have quantified how subglacial conduit roughness evolves over time or how that evolution affects models of conduit enlargement. To address this knowledge gap, we calculated values for two roughness parameters, the Darcy-Weisbach friction factor (f) and the Manning roughness coefficient (n), using dye tracing data from a mapped subglacial conduit at Rieperbreen, Svalbard. Values of f and n calculated from dye traces were compared with values of f and n calculated from commonly used relationships between surface roughness heights and conduit hydraulic diameters. Roughness values calculated from dye tracing ranged from 75-0.97 for f and from 0.68-0.09 s m-1/3 for n. Equations that calculate roughness parameters from surface roughness heights underpredicted values of f by as much as a factor of 326 and values of n by a factor of 17 relative to values obtained from the dye tracing study. We argue these large underpredictions occur because relative roughness in subglacial conduits during the early stages of conduit enlargement exceeds the 5% range of relative roughness that can be used to directly relate values of f and n to flow depth and surface roughness heights. Simple conduit hydrological models presented here show how parameterization of roughness impacts models of conduit discharge and enlargement rate. We used relationships between conduit relative roughness and values of f and n calculated from our dye tracing study to parameterize a model of conduit enlargement. Assuming a fixed hydraulic gradient of 0.01 and ignoring creep closure, it took conduits 9.25 days to enlarge from a diameter of 0.44 m to 3 m, which was 6-7-fold longer than using common roughness parameterizations. Text glacier Svalbard Michigan Technological University: Digital Commons @ Michigan Tech Rieperbreen ENVELOPE(16.067,16.067,78.133,78.133) Svalbard Earth Surface Processes and Landforms 39 3 296 310 |
institution |
Open Polar |
collection |
Michigan Technological University: Digital Commons @ Michigan Tech |
op_collection_id |
ftmichigantuniv |
language |
unknown |
topic |
Englacial Friction factor Glacier hydrology Roughness Subglacial Department of Geological and Mining Engineering and Sciences Department of Civil Environmental and Geospatial Engineering Civil and Environmental Engineering Geological Engineering Mining Engineering |
spellingShingle |
Englacial Friction factor Glacier hydrology Roughness Subglacial Department of Geological and Mining Engineering and Sciences Department of Civil Environmental and Geospatial Engineering Civil and Environmental Engineering Geological Engineering Mining Engineering Gulley, J. D. Spellman, P. Covington, M. D. Martin, J. B. Benn, D. I. Catania, G. Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution |
topic_facet |
Englacial Friction factor Glacier hydrology Roughness Subglacial Department of Geological and Mining Engineering and Sciences Department of Civil Environmental and Geospatial Engineering Civil and Environmental Engineering Geological Engineering Mining Engineering |
description |
Hydraulic roughness accounts for energy dissipated as heat and should exert an important control on rates of subglacial conduit enlargement by melting. Few studies, however, have quantified how subglacial conduit roughness evolves over time or how that evolution affects models of conduit enlargement. To address this knowledge gap, we calculated values for two roughness parameters, the Darcy-Weisbach friction factor (f) and the Manning roughness coefficient (n), using dye tracing data from a mapped subglacial conduit at Rieperbreen, Svalbard. Values of f and n calculated from dye traces were compared with values of f and n calculated from commonly used relationships between surface roughness heights and conduit hydraulic diameters. Roughness values calculated from dye tracing ranged from 75-0.97 for f and from 0.68-0.09 s m-1/3 for n. Equations that calculate roughness parameters from surface roughness heights underpredicted values of f by as much as a factor of 326 and values of n by a factor of 17 relative to values obtained from the dye tracing study. We argue these large underpredictions occur because relative roughness in subglacial conduits during the early stages of conduit enlargement exceeds the 5% range of relative roughness that can be used to directly relate values of f and n to flow depth and surface roughness heights. Simple conduit hydrological models presented here show how parameterization of roughness impacts models of conduit discharge and enlargement rate. We used relationships between conduit relative roughness and values of f and n calculated from our dye tracing study to parameterize a model of conduit enlargement. Assuming a fixed hydraulic gradient of 0.01 and ignoring creep closure, it took conduits 9.25 days to enlarge from a diameter of 0.44 m to 3 m, which was 6-7-fold longer than using common roughness parameterizations. |
format |
Text |
author |
Gulley, J. D. Spellman, P. Covington, M. D. Martin, J. B. Benn, D. I. Catania, G. |
author_facet |
Gulley, J. D. Spellman, P. Covington, M. D. Martin, J. B. Benn, D. I. Catania, G. |
author_sort |
Gulley, J. D. |
title |
Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution |
title_short |
Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution |
title_full |
Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution |
title_fullStr |
Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution |
title_full_unstemmed |
Large values of hydraulic roughness in subglacial conduits during conduit enlargement: Implications for modeling conduit evolution |
title_sort |
large values of hydraulic roughness in subglacial conduits during conduit enlargement: implications for modeling conduit evolution |
publisher |
Digital Commons @ Michigan Tech |
publishDate |
2014 |
url |
https://digitalcommons.mtu.edu/michigantech-p/3619 https://doi.org/10.1002/esp.3447 |
long_lat |
ENVELOPE(16.067,16.067,78.133,78.133) |
geographic |
Rieperbreen Svalbard |
geographic_facet |
Rieperbreen Svalbard |
genre |
glacier Svalbard |
genre_facet |
glacier Svalbard |
op_source |
Michigan Tech Publications |
op_relation |
https://digitalcommons.mtu.edu/michigantech-p/3619 https://doi.org/10.1002/esp.3447 |
op_doi |
https://doi.org/10.1002/esp.3447 |
container_title |
Earth Surface Processes and Landforms |
container_volume |
39 |
container_issue |
3 |
container_start_page |
296 |
op_container_end_page |
310 |
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1766010259673972736 |