Clark, Chris D.

Dunlop, P

Ely, J.

Greenwood, S.L.

Hess, D.

Hughs, A.L.C

Spagnolo, M

Stokes, Chris

English

Ice sheet flow organises sediment into undulating landforms called subglacial bedforms, making their genesis pertinent to understanding ice flow mechanics. Currently, there is a lack of consensus regarding their formation. An array of different theories exist which seek to explain specific types of bedform, e.g. flutes, drumlins, ribbed moraine, mega-scale glacial lineations (MSGL). In contrast, other theories appeal to the hypothesis that these landforms are actually the same phenomena that steadily vary on a scale and shape continuum and that possibly share the same mechanism of formation. Here we test the idea of a continuum by analysing the largest dataset of subglacial bedform morphometrics ever reported (n ≡ 100,000). Scatter graphs of bedform size and shape metrics (length, width and elongation) reveal two separate clouds of data. The first is comprised of flutes, which form a separate distinct cluster to all other subglacial bedforms. The second, much larger, cloud of data comprises all remaining subglacial bedforms, which form a continuum of size and shape metrics. Hence, it is impossible to quantitatively differentiate previously assigned and commonly used landform labels based on their morphometry. Drumlins merge into MSGL forming subglacial lineations (aligned with flow direction), and these are adjoined to subglacial ribs (orthogonal to flow) by quasi-circular bedforms which occur within transition zones between ribbed moraine and drumlins. We interpret this as showing that a separate mechanism is required for flute generation and that the other landforms sit along a subglacial bedform continuum of ribs-circles-lineations, consistent with unifying theories for their formation

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Geophysical Research AbstractsVol. 16, EGU2014-5533, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Demonstration of a subglacial bedform continuum: Is a unifyingformation theory required?Jeremy C. Ely (1), Chris D. Clark (1), Matteo Spagnolo (2), Chris R. Stokes (3), Sarah L. Greenwood (4), AnnaL. C. Hughes (5), Paul Dunlop (6), and Dale Hess (7)(1) Department of Geography, University of Sheffield, Sheffield, UK (gga08je@shef.ac.uk; c.clark@shef.ac.uk), (2) School ofGeosciences, University of Aberdeen, Aberdeen, UK (m.spagnolo@abdn.ac.uk), (3) Department of Geography, DurhamUniversity, Durham, UK (c.r.stokes@durham.ac.uk), (4) Department of Geological Sciences, Stockholm University,Stockholm, Sweden (sarah.greenwood@geo.su.se), (5) Department of Earth Science, University of Bergen, Bergen, Norway(anna.hughes@geo.uib.no), (6) School of Environmental Sciences, University of Ulster, Coleraine (p.dunlop@ulster.ac.uk),(7) Department of Earth and Environmental Sciences, The University of Rochester, Rochester, New York, United States(dalehess@gmail.com)Ice sheet flow organises sediment into undulating landforms called subglacial bedforms, making their genesispertinent to understanding ice flow mechanics. Currently, there is a lack of consensus regarding their formation.An array of different theories exist which seek to explain specific types of bedform, e.g. flutes, drumlins, ribbedmoraine, mega-scale glacial lineations (MSGL). In contrast, other theories appeal to the hypothesis that theselandforms are actually the same phenomena that steadily vary on a scale and shape continuum and that possiblyshare the same mechanism of formation. Here we test the idea of a continuum by analysing the largest dataset ofsubglacial bedform morphometrics ever reported (n ≈ 100,000). Scatter graphs of bedform size and shape metrics(length, width and elongation) reveal two separate clouds of data. The first is comprised of flutes, which form aseparate distinct cluster to all other subglacial bedforms. The second, much larger, cloud of data comprises allremaining subglacial bedforms, which form a continuum of size and shape metrics. Hence, it is impossible toquantitatively differentiate previously assigned and commonly used landform labels based on their morphometry.Drumlins merge into MSGL forming subglacial lineations (aligned with flow direction), and these are adjoined tosubglacial ribs (orthogonal to flow) by quasi-circular bedforms which occur within transition zones between ribbedmoraine and drumlins. We interpret this as showing that a separate mechanism is required for flute generationand that the other landforms sit along a subglacial bedform continuum of ribs-circles-lineations, consistent withunifying theories for their formation.

Demonstration of a subglacial bedform continuum: Is a unifying formation theory required?:Geophysical Research Abstracts Vol. 16, EGU2014-5533, 2014

https://pure.ulster.ac.uk/ws/files/77542119/EGU2014_5533.pdf

Demonstration of a subglacial bedform continuum: Is a unifying formation theory required?:Geophysical Research Abstracts Vol. 16, EGU2014-5533, 2014

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