Bed Ribbing Instability Explanation: Testing a numerical model of ribbed moraine formation arising from coupled flow of ice and subglacial sediment

P Dunlop; C.D. Clark; R.C.A Hindmarsh

doi:10.1029/2007JF000954

Bed Ribbing Instability Explanation: Testing a numerical model of ribbed moraine formation arising from coupled flow of ice and subglacial sediment

P Dunlop, C.D. Clark, R.C.A Hindmarsh

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

75 Citations (Scopus)

127 Downloads (Pure)

Abstract

Ribbed moraines are large (up to 16 km long) ridges of sediment produced transverseto ice flow direction that formed widely beneath palaeo-ice sheets. Since ice sheetstability is sensitive to conditions operating at the bed, an understanding of ribbedmoraine genesis will provide critical information on ice sheet dynamics. Currently, thereis no consensus on ribbed moraine formation and various competing hypotheses havebeen presented to account for their genesis. Only one of these theories has beendeveloped into a physically based numerical model that quantitatively describes ribbedmoraine formation. This theory, known as the Bed Ribbing Instability Explanation(BRIE), argues that ribbed moraines are produced by a naturally arising instability in thecoupled flow of ice and till. BRIE demonstrates that transverse subglacial ridges (i.e.,ribbed moraine) spontaneously grow under certain parameter combinations, and itpredicts their wavelength (spacing between ridges). The model represents a significantadvance because it is the first time a theory of subglacial bedform generation has beendeveloped to make quantitative predictions which can be formally tested. This paperdiscusses the types of tests that are currently possible and reports the results from the firsttesting of BRIE. This analysis centers on the ability of BRIE to predict the primarycharacteristics of ribbed moraine, which are patterning and wavelength. Results show thatBRIE successfully predicts the correct ribbed moraine pattern and appropriate wavelengths.The tests fail to falsify the model, and it is concluded that BRIE remains a viableexplanation of ribbed moraine formation.

Original language	English
Pages (from-to)	1-15
Journal	Journal of Geophysical Research
Volume	113
Issue number	F03005
DOIs	https://doi.org/10.1029/2007JF000954
Publication status	Published (in print/issue) - 24 Jul 2008

Bibliographical note

Reference text: Alley, R. B., D. D. Blankenship, S. T. Rooney, and C. R. Bentley (1989),
Water-pressure coupling of sliding and bed deformation: III. Application
to Ice Stream B, Antarctica, J. Glaciol., 35, 130– 139.

Ashton, A., A. B. Murray, and O. Arnoult (2001), Formation of coastline
features by large-scale instabilities induced by high-angle waves, Nature,
414, 296–300, doi:10.1038/35104541.

Aylsworth, J. M., and W. W. Shilts (1989), Bedforms of the Keewatin Ice
Sheet, Canada, Sediment. Geol., 62, 407 – 428, doi:10.1016/0037-
0738(89)90129-2.

Beskow, G. (1935), Patriska och kvarta¨rgeologiska resultat av grusinventeringen
I Norrbottens lan, Geol. Foeren. Stockholm Foerh., 57, 120–123.

Blatter, H. (1995), Velocity and stress-fields in grounded glaciers—A simple
algorithm for including deviatoric stress gradients, J. Glaciol.,
41(138), 333– 344.

Bouchard, M. A. (1989), Subglacial landforms and deposits in central and
northern Quebec, Canada, with emphasis on Rogen moraines, Sediment.
Geol., 62, 293–308, doi:10.1016/0037-0738(89)90120-6.

Boulton, G. S. (1987), A theory of drumlin formation by subglacial deformation.
In Drumlin Symposium, eds J. Menzies and J. Rose, Balkema,
Rotterdam, 25– 80.

Clark, C. D., and R. Meehan (2001), Subglacial bedform geomorphology of
the Irish Ice Sheet reveals major configuration changes during growth
and decay, J. Quaternary Sci., 16, 483– 496, doi:10.1002/jqs.627.

Dunlop, P. (2004), The Characteristics of ribbed moraine and assessment of
theories for their genesis, Ph.D. thesis, 363 pp., Univ. of Sheffield, Sheffield,
U. K.

Dunlop, P., and C. D. Clark (2006a), The morphological characteristics of
ribbed moraine, Quat. Sci. Rev., 25, 1668– 1691, doi:10.1016/j.quascirev.
2006.01.002.

Dunlop, P., and C. D. Clark (2006b), The distribution of ribbed moraines in
the Lac Naococane region, central Quebec, Canada, J. Maps, 56–67.
Drazen, P. G. (2002), Introduction to Hydrodynamic Stability, Cambridge
Univ. Press, Cambridge, U. K.

Dyke, A. S., T. F. Morris, D. E. C. Green, and J. England (1992), Quaternary
geology of Prince of Wales Island, arctic Canada, Geol. Surv. Can.
Mem. Ser., vol. 433, Geol. Surv. of Can., Ottawa, Ont.

Elbelrhiti, H., P. Claudin, and B. Andreotti (2005), Field evidence for surface-
wave-induced instability of sand dunes, Nature, 437, 720 – 723,
doi:10.1038/nature04058.

Fisher, T. G., and J. Shaw (1992), A depositional model for Rogen moraine,
with examples from the Avalon Peninsula, Newfoundland, Can. J. Earth
Sci., 29, 669– 686.

Fowler, A. C. (2000), An instability mechanism for drumlin formation, in
Deformation of Glacial Materials, Spec. Publ. Geol. Soc. Ser., vol. 176,
edited by A. Maltman, M. J. Hambrey, and B. Hubbard, pp. 307– 319,
Geol. Soc. of Am., Boulder, Colo.

Frodin, G. (1913), Bidrag till va¨stra Jamtlands senglaciala geologi, Sver.
Geol. Unders. Ser. C, 246, 1– 236.

Frodin, G. (1925), Studien u¨ber die Eissheide in Zentralskandinavien, Bull.
of the Geol. Inst. at Univ. Upsala, 19, 129– 214.

Getling, A. V. (1997), Rayleigh-Be´nard Convection Structures and Dynamics,
Adv. Ser. Nonlinear Dyn., vol. 11, World Sci., London.

Ha¨ttestrand, C. (1997), Ribbed moraines in Sweden—Distribution pattern
and palaeoglaciological implications, Sediment. Geol., 111, 41–56,
doi:10.1016/S0037-0738(97)00005-5.

Hattestrand, C., and J. Kleman (1999), Ribbed moraine formation, Quat.
Sci. Rev., 18, 43– 61, doi:10.1016/S0277-3791(97)00094-2.

Hersen, P., K. H. Andersen, H. Elbelrhiti, B. Andreotti, P. Claudin, and
S. Douady (2004), Corridors of barchan dunes: Stability and size selection,
Phys. Rev. E, 69, 1– 12.

Hindmarsh, R. C. A. (1997), Deforming beds: Viscous and plastic scales of
deformation, Quat. Sci. Rev., 16, 1039 – 1056, doi:10.1016/S0277-
3791(97)00035-8.

Hindmarsh, R. C. A. (1998a), The stability of a viscous till sheet coupled
with ice flow, considered at wavelengths less than ice thickness, J. Glaciol.,
44, 288– 292.

Hindmarsh, R. C. A. (1998b), Drumlinization and drumlin-forming instabilities:
Viscous till mechanisms, J. Glaciol., 44, 293– 314.

Hindmarsh, R. C. A. (1998c), Ice-stream surface texture, sticky-spots,
waves and breathers: The Couples flow of ice, till and water, J. Glaciol.,
44, 589– 614.

Hindmarsh, R. C. A. (1999), Coupled ice-till dynamics and the seeding of
drumlins and bedrock forms, Ann. Glaciol., 28, 221– 230, doi:10.3189/
172756499781821931.

Hogbom, A. G. (1920), Geologisk Beskrivning Over Jemtlands La¨n,
2nd ed., Sver. Geol. Unders. Ser. C, vol. 140, Redins Antikvariat, Uppsala,
Sweden.

Hoppe, G. (1952), Hummocky moraine regions, with special reference to
the interior of Norrbotten, Geogr. Ann., 41A, 193– 212.
Hutter, K. (1983), Theoretical Glaciology, D. Riedel, Dordrecht,
Netherlands.

Jackson, M., and B. Kamb (1997), Marginal shear stress of ice stream B,
J. Glaciol., 43, 415– 426.

Joughin, I., W. Abdalati, and M. Fahnestock (2004), Large fluctuations in
speed on Greenland’s Jakobshavn Isbrae glacier, Nature, 432(7017),
608– 610, doi:10.1038/nature03130.

Knight, J., and A. M. McCabe (1997), Identification and significance of iceflow
transverse subglacial ridges (Rogen moraines) in northern central
Ireland, J. Quaternary Sci., 12(6), 519 – 534, doi:10.1002/(SICI)1099-
1417(199711/12)12:6<519::AID-JQS313>3.0.CO;2-Q.

Komarova, N. L., and S. J. M. H. Hulscher (2000), Linear instability
mechanisms for sand wave formation, J. Fluid Mech., 413, 219– 246,
doi:10.1017/S0022112000008429.

Kurimo, H. (1977), Patterns of dead-ice deglaciation forms in western
kemijarvi, northern Finland, Fennia, 153, 43– 56.

Kurimo, H. (1980), Depositional deglaciation forms as indicators of different
glaciomarginal environments, Boreas, 9, 179–191.

Lundqvist, J. (1951), Beskrivning Till Jordartskarta O¨ ver Kopparbergs
Lan, Sver. Geol. Unders. Ser. C, vol. 21, Redins Antikvariat, Uppsala,
Sweden.

Keywords

Ribbed Moraine
Instability
modelling

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Cite this

@article{7f3ff915a63b4dec84d804e8cd0207d5,

title = "Bed Ribbing Instability Explanation: Testing a numerical model of ribbed moraine formation arising from coupled flow of ice and subglacial sediment",

abstract = "Ribbed moraines are large (up to 16 km long) ridges of sediment produced transverseto ice flow direction that formed widely beneath palaeo-ice sheets. Since ice sheetstability is sensitive to conditions operating at the bed, an understanding of ribbedmoraine genesis will provide critical information on ice sheet dynamics. Currently, thereis no consensus on ribbed moraine formation and various competing hypotheses havebeen presented to account for their genesis. Only one of these theories has beendeveloped into a physically based numerical model that quantitatively describes ribbedmoraine formation. This theory, known as the Bed Ribbing Instability Explanation(BRIE), argues that ribbed moraines are produced by a naturally arising instability in thecoupled flow of ice and till. BRIE demonstrates that transverse subglacial ridges (i.e.,ribbed moraine) spontaneously grow under certain parameter combinations, and itpredicts their wavelength (spacing between ridges). The model represents a significantadvance because it is the first time a theory of subglacial bedform generation has beendeveloped to make quantitative predictions which can be formally tested. This paperdiscusses the types of tests that are currently possible and reports the results from the firsttesting of BRIE. This analysis centers on the ability of BRIE to predict the primarycharacteristics of ribbed moraine, which are patterning and wavelength. Results show thatBRIE successfully predicts the correct ribbed moraine pattern and appropriate wavelengths.The tests fail to falsify the model, and it is concluded that BRIE remains a viableexplanation of ribbed moraine formation.",

keywords = "Ribbed Moraine, Instability, modelling",

author = "P Dunlop and C.D. Clark and R.C.A Hindmarsh",

note = "Reference text: Alley, R. B., D. D. Blankenship, S. T. Rooney, and C. R. Bentley (1989), Water-pressure coupling of sliding and bed deformation: III. Application to Ice Stream B, Antarctica, J. Glaciol., 35, 130– 139. Ashton, A., A. B. Murray, and O. Arnoult (2001), Formation of coastline features by large-scale instabilities induced by high-angle waves, Nature, 414, 296–300, doi:10.1038/35104541. Aylsworth, J. M., and W. W. Shilts (1989), Bedforms of the Keewatin Ice Sheet, Canada, Sediment. Geol., 62, 407 – 428, doi:10.1016/0037- 0738(89)90129-2. Beskow, G. (1935), Patriska och kvarta¨rgeologiska resultat av grusinventeringen I Norrbottens lan, Geol. Foeren. Stockholm Foerh., 57, 120–123. Blatter, H. (1995), Velocity and stress-fields in grounded glaciers—A simple algorithm for including deviatoric stress gradients, J. Glaciol., 41(138), 333– 344. Bouchard, M. A. (1989), Subglacial landforms and deposits in central and northern Quebec, Canada, with emphasis on Rogen moraines, Sediment. Geol., 62, 293–308, doi:10.1016/0037-0738(89)90120-6. Boulton, G. S. (1987), A theory of drumlin formation by subglacial deformation. In Drumlin Symposium, eds J. Menzies and J. Rose, Balkema, Rotterdam, 25– 80. Clark, C. D., and R. Meehan (2001), Subglacial bedform geomorphology of the Irish Ice Sheet reveals major configuration changes during growth and decay, J. Quaternary Sci., 16, 483– 496, doi:10.1002/jqs.627. Dunlop, P. (2004), The Characteristics of ribbed moraine and assessment of theories for their genesis, Ph.D. thesis, 363 pp., Univ. of Sheffield, Sheffield, U. K. Dunlop, P., and C. D. Clark (2006a), The morphological characteristics of ribbed moraine, Quat. Sci. Rev., 25, 1668– 1691, doi:10.1016/j.quascirev. 2006.01.002. Dunlop, P., and C. D. Clark (2006b), The distribution of ribbed moraines in the Lac Naococane region, central Quebec, Canada, J. Maps, 56–67. Drazen, P. G. (2002), Introduction to Hydrodynamic Stability, Cambridge Univ. Press, Cambridge, U. K. Dyke, A. S., T. F. Morris, D. E. C. Green, and J. England (1992), Quaternary geology of Prince of Wales Island, arctic Canada, Geol. Surv. Can. Mem. Ser., vol. 433, Geol. Surv. of Can., Ottawa, Ont. Elbelrhiti, H., P. Claudin, and B. Andreotti (2005), Field evidence for surface- wave-induced instability of sand dunes, Nature, 437, 720 – 723, doi:10.1038/nature04058. Fisher, T. G., and J. Shaw (1992), A depositional model for Rogen moraine, with examples from the Avalon Peninsula, Newfoundland, Can. J. Earth Sci., 29, 669– 686. Fowler, A. C. (2000), An instability mechanism for drumlin formation, in Deformation of Glacial Materials, Spec. Publ. Geol. Soc. Ser., vol. 176, edited by A. Maltman, M. J. Hambrey, and B. Hubbard, pp. 307– 319, Geol. Soc. of Am., Boulder, Colo. Frodin, G. (1913), Bidrag till va¨stra Jamtlands senglaciala geologi, Sver. Geol. Unders. Ser. C, 246, 1– 236. Frodin, G. (1925), Studien u¨ber die Eissheide in Zentralskandinavien, Bull. of the Geol. Inst. at Univ. Upsala, 19, 129– 214. Getling, A. V. (1997), Rayleigh-Be´nard Convection Structures and Dynamics, Adv. Ser. Nonlinear Dyn., vol. 11, World Sci., London. Ha¨ttestrand, C. (1997), Ribbed moraines in Sweden—Distribution pattern and palaeoglaciological implications, Sediment. Geol., 111, 41–56, doi:10.1016/S0037-0738(97)00005-5. Hattestrand, C., and J. Kleman (1999), Ribbed moraine formation, Quat. Sci. Rev., 18, 43– 61, doi:10.1016/S0277-3791(97)00094-2. Hersen, P., K. H. Andersen, H. Elbelrhiti, B. Andreotti, P. Claudin, and S. Douady (2004), Corridors of barchan dunes: Stability and size selection, Phys. Rev. E, 69, 1– 12. Hindmarsh, R. C. A. (1997), Deforming beds: Viscous and plastic scales of deformation, Quat. Sci. Rev., 16, 1039 – 1056, doi:10.1016/S0277- 3791(97)00035-8. Hindmarsh, R. C. A. (1998a), The stability of a viscous till sheet coupled with ice flow, considered at wavelengths less than ice thickness, J. Glaciol., 44, 288– 292. Hindmarsh, R. C. A. (1998b), Drumlinization and drumlin-forming instabilities: Viscous till mechanisms, J. Glaciol., 44, 293– 314. Hindmarsh, R. C. A. (1998c), Ice-stream surface texture, sticky-spots, waves and breathers: The Couples flow of ice, till and water, J. Glaciol., 44, 589– 614. Hindmarsh, R. C. A. (1999), Coupled ice-till dynamics and the seeding of drumlins and bedrock forms, Ann. Glaciol., 28, 221– 230, doi:10.3189/ 172756499781821931. Hogbom, A. G. (1920), Geologisk Beskrivning Over Jemtlands La¨n, 2nd ed., Sver. Geol. Unders. Ser. C, vol. 140, Redins Antikvariat, Uppsala, Sweden. Hoppe, G. (1952), Hummocky moraine regions, with special reference to the interior of Norrbotten, Geogr. Ann., 41A, 193– 212. Hutter, K. (1983), Theoretical Glaciology, D. Riedel, Dordrecht, Netherlands. Jackson, M., and B. Kamb (1997), Marginal shear stress of ice stream B, J. Glaciol., 43, 415– 426. Joughin, I., W. Abdalati, and M. Fahnestock (2004), Large fluctuations in speed on Greenland{\textquoteright}s Jakobshavn Isbrae glacier, Nature, 432(7017), 608– 610, doi:10.1038/nature03130. Knight, J., and A. M. McCabe (1997), Identification and significance of iceflow transverse subglacial ridges (Rogen moraines) in northern central Ireland, J. Quaternary Sci., 12(6), 519 – 534, doi:10.1002/(SICI)1099- 1417(199711/12)12:6<519::AID-JQS313>3.0.CO;2-Q. Komarova, N. L., and S. J. M. H. Hulscher (2000), Linear instability mechanisms for sand wave formation, J. Fluid Mech., 413, 219– 246, doi:10.1017/S0022112000008429. Kurimo, H. (1977), Patterns of dead-ice deglaciation forms in western kemijarvi, northern Finland, Fennia, 153, 43– 56. Kurimo, H. (1980), Depositional deglaciation forms as indicators of different glaciomarginal environments, Boreas, 9, 179–191. Lundqvist, J. (1951), Beskrivning Till Jordartskarta O¨ ver Kopparbergs Lan, Sver. Geol. Unders. Ser. C, vol. 21, Redins Antikvariat, Uppsala, Sweden.",

year = "2008",

month = jul,

day = "24",

doi = "10.1029/2007JF000954",

language = "English",

volume = "113",

pages = "1--15",

journal = "Journal of Geophysical Research",

issn = "2156-2202",

publisher = "American Geophysical Union",

number = "F03005",

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TY - JOUR

T1 - Bed Ribbing Instability Explanation: Testing a numerical model of ribbed moraine formation arising from coupled flow of ice and subglacial sediment

AU - Dunlop, P

AU - Clark, C.D.

AU - Hindmarsh, R.C.A

N1 - Reference text: Alley, R. B., D. D. Blankenship, S. T. Rooney, and C. R. Bentley (1989), Water-pressure coupling of sliding and bed deformation: III. Application to Ice Stream B, Antarctica, J. Glaciol., 35, 130– 139. Ashton, A., A. B. Murray, and O. Arnoult (2001), Formation of coastline features by large-scale instabilities induced by high-angle waves, Nature, 414, 296–300, doi:10.1038/35104541. Aylsworth, J. M., and W. W. Shilts (1989), Bedforms of the Keewatin Ice Sheet, Canada, Sediment. Geol., 62, 407 – 428, doi:10.1016/0037- 0738(89)90129-2. Beskow, G. (1935), Patriska och kvarta¨rgeologiska resultat av grusinventeringen I Norrbottens lan, Geol. Foeren. Stockholm Foerh., 57, 120–123. Blatter, H. (1995), Velocity and stress-fields in grounded glaciers—A simple algorithm for including deviatoric stress gradients, J. Glaciol., 41(138), 333– 344. Bouchard, M. A. (1989), Subglacial landforms and deposits in central and northern Quebec, Canada, with emphasis on Rogen moraines, Sediment. Geol., 62, 293–308, doi:10.1016/0037-0738(89)90120-6. Boulton, G. S. (1987), A theory of drumlin formation by subglacial deformation. In Drumlin Symposium, eds J. Menzies and J. Rose, Balkema, Rotterdam, 25– 80. Clark, C. D., and R. Meehan (2001), Subglacial bedform geomorphology of the Irish Ice Sheet reveals major configuration changes during growth and decay, J. Quaternary Sci., 16, 483– 496, doi:10.1002/jqs.627. Dunlop, P. (2004), The Characteristics of ribbed moraine and assessment of theories for their genesis, Ph.D. thesis, 363 pp., Univ. of Sheffield, Sheffield, U. K. Dunlop, P., and C. D. Clark (2006a), The morphological characteristics of ribbed moraine, Quat. Sci. Rev., 25, 1668– 1691, doi:10.1016/j.quascirev. 2006.01.002. Dunlop, P., and C. D. Clark (2006b), The distribution of ribbed moraines in the Lac Naococane region, central Quebec, Canada, J. Maps, 56–67. Drazen, P. G. (2002), Introduction to Hydrodynamic Stability, Cambridge Univ. Press, Cambridge, U. K. Dyke, A. S., T. F. Morris, D. E. C. Green, and J. England (1992), Quaternary geology of Prince of Wales Island, arctic Canada, Geol. Surv. Can. Mem. Ser., vol. 433, Geol. Surv. of Can., Ottawa, Ont. Elbelrhiti, H., P. Claudin, and B. Andreotti (2005), Field evidence for surface- wave-induced instability of sand dunes, Nature, 437, 720 – 723, doi:10.1038/nature04058. Fisher, T. G., and J. Shaw (1992), A depositional model for Rogen moraine, with examples from the Avalon Peninsula, Newfoundland, Can. J. Earth Sci., 29, 669– 686. Fowler, A. C. (2000), An instability mechanism for drumlin formation, in Deformation of Glacial Materials, Spec. Publ. Geol. Soc. Ser., vol. 176, edited by A. Maltman, M. J. Hambrey, and B. Hubbard, pp. 307– 319, Geol. Soc. of Am., Boulder, Colo. Frodin, G. (1913), Bidrag till va¨stra Jamtlands senglaciala geologi, Sver. Geol. Unders. Ser. C, 246, 1– 236. Frodin, G. (1925), Studien u¨ber die Eissheide in Zentralskandinavien, Bull. of the Geol. Inst. at Univ. Upsala, 19, 129– 214. Getling, A. V. (1997), Rayleigh-Be´nard Convection Structures and Dynamics, Adv. Ser. Nonlinear Dyn., vol. 11, World Sci., London. Ha¨ttestrand, C. (1997), Ribbed moraines in Sweden—Distribution pattern and palaeoglaciological implications, Sediment. Geol., 111, 41–56, doi:10.1016/S0037-0738(97)00005-5. Hattestrand, C., and J. Kleman (1999), Ribbed moraine formation, Quat. Sci. Rev., 18, 43– 61, doi:10.1016/S0277-3791(97)00094-2. Hersen, P., K. H. Andersen, H. Elbelrhiti, B. Andreotti, P. Claudin, and S. Douady (2004), Corridors of barchan dunes: Stability and size selection, Phys. Rev. E, 69, 1– 12. Hindmarsh, R. C. A. (1997), Deforming beds: Viscous and plastic scales of deformation, Quat. Sci. Rev., 16, 1039 – 1056, doi:10.1016/S0277- 3791(97)00035-8. Hindmarsh, R. C. A. (1998a), The stability of a viscous till sheet coupled with ice flow, considered at wavelengths less than ice thickness, J. Glaciol., 44, 288– 292. Hindmarsh, R. C. A. (1998b), Drumlinization and drumlin-forming instabilities: Viscous till mechanisms, J. Glaciol., 44, 293– 314. Hindmarsh, R. C. A. (1998c), Ice-stream surface texture, sticky-spots, waves and breathers: The Couples flow of ice, till and water, J. Glaciol., 44, 589– 614. Hindmarsh, R. C. A. (1999), Coupled ice-till dynamics and the seeding of drumlins and bedrock forms, Ann. Glaciol., 28, 221– 230, doi:10.3189/ 172756499781821931. Hogbom, A. G. (1920), Geologisk Beskrivning Over Jemtlands La¨n, 2nd ed., Sver. Geol. Unders. Ser. C, vol. 140, Redins Antikvariat, Uppsala, Sweden. Hoppe, G. (1952), Hummocky moraine regions, with special reference to the interior of Norrbotten, Geogr. Ann., 41A, 193– 212. Hutter, K. (1983), Theoretical Glaciology, D. Riedel, Dordrecht, Netherlands. Jackson, M., and B. Kamb (1997), Marginal shear stress of ice stream B, J. Glaciol., 43, 415– 426. Joughin, I., W. Abdalati, and M. Fahnestock (2004), Large fluctuations in speed on Greenland’s Jakobshavn Isbrae glacier, Nature, 432(7017), 608– 610, doi:10.1038/nature03130. Knight, J., and A. M. McCabe (1997), Identification and significance of iceflow transverse subglacial ridges (Rogen moraines) in northern central Ireland, J. Quaternary Sci., 12(6), 519 – 534, doi:10.1002/(SICI)1099- 1417(199711/12)12:6<519::AID-JQS313>3.0.CO;2-Q. Komarova, N. L., and S. J. M. H. Hulscher (2000), Linear instability mechanisms for sand wave formation, J. Fluid Mech., 413, 219– 246, doi:10.1017/S0022112000008429. Kurimo, H. (1977), Patterns of dead-ice deglaciation forms in western kemijarvi, northern Finland, Fennia, 153, 43– 56. Kurimo, H. (1980), Depositional deglaciation forms as indicators of different glaciomarginal environments, Boreas, 9, 179–191. Lundqvist, J. (1951), Beskrivning Till Jordartskarta O¨ ver Kopparbergs Lan, Sver. Geol. Unders. Ser. C, vol. 21, Redins Antikvariat, Uppsala, Sweden.

PY - 2008/7/24

Y1 - 2008/7/24

N2 - Ribbed moraines are large (up to 16 km long) ridges of sediment produced transverseto ice flow direction that formed widely beneath palaeo-ice sheets. Since ice sheetstability is sensitive to conditions operating at the bed, an understanding of ribbedmoraine genesis will provide critical information on ice sheet dynamics. Currently, thereis no consensus on ribbed moraine formation and various competing hypotheses havebeen presented to account for their genesis. Only one of these theories has beendeveloped into a physically based numerical model that quantitatively describes ribbedmoraine formation. This theory, known as the Bed Ribbing Instability Explanation(BRIE), argues that ribbed moraines are produced by a naturally arising instability in thecoupled flow of ice and till. BRIE demonstrates that transverse subglacial ridges (i.e.,ribbed moraine) spontaneously grow under certain parameter combinations, and itpredicts their wavelength (spacing between ridges). The model represents a significantadvance because it is the first time a theory of subglacial bedform generation has beendeveloped to make quantitative predictions which can be formally tested. This paperdiscusses the types of tests that are currently possible and reports the results from the firsttesting of BRIE. This analysis centers on the ability of BRIE to predict the primarycharacteristics of ribbed moraine, which are patterning and wavelength. Results show thatBRIE successfully predicts the correct ribbed moraine pattern and appropriate wavelengths.The tests fail to falsify the model, and it is concluded that BRIE remains a viableexplanation of ribbed moraine formation.

AB - Ribbed moraines are large (up to 16 km long) ridges of sediment produced transverseto ice flow direction that formed widely beneath palaeo-ice sheets. Since ice sheetstability is sensitive to conditions operating at the bed, an understanding of ribbedmoraine genesis will provide critical information on ice sheet dynamics. Currently, thereis no consensus on ribbed moraine formation and various competing hypotheses havebeen presented to account for their genesis. Only one of these theories has beendeveloped into a physically based numerical model that quantitatively describes ribbedmoraine formation. This theory, known as the Bed Ribbing Instability Explanation(BRIE), argues that ribbed moraines are produced by a naturally arising instability in thecoupled flow of ice and till. BRIE demonstrates that transverse subglacial ridges (i.e.,ribbed moraine) spontaneously grow under certain parameter combinations, and itpredicts their wavelength (spacing between ridges). The model represents a significantadvance because it is the first time a theory of subglacial bedform generation has beendeveloped to make quantitative predictions which can be formally tested. This paperdiscusses the types of tests that are currently possible and reports the results from the firsttesting of BRIE. This analysis centers on the ability of BRIE to predict the primarycharacteristics of ribbed moraine, which are patterning and wavelength. Results show thatBRIE successfully predicts the correct ribbed moraine pattern and appropriate wavelengths.The tests fail to falsify the model, and it is concluded that BRIE remains a viableexplanation of ribbed moraine formation.

KW - Ribbed Moraine

KW - Instability

KW - modelling

UR - http://www.agu.org/pubs/

U2 - 10.1029/2007JF000954

DO - 10.1029/2007JF000954

M3 - Article

SN - 2156-2202

VL - 113

SP - 1

EP - 15

JO - Journal of Geophysical Research

JF - Journal of Geophysical Research

IS - F03005

ER -

Bed Ribbing Instability Explanation: Testing a numerical model of ribbed moraine formation arising from coupled flow of ice and subglacial sediment

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Testing a numerical model of ribbed moraine formation arising from an instability in the coupled flow of ice and subglacial sediment: 2008AGUFM.C23B..06D

The Characteristics of Ribbed Moraine and Assessment of Theories for Their Genesis

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