Subglacial bedform morphology controlled by ice speed and sediment thickness.

• Published in: Geophysical Research Letters
• Main Authors: Barchyn, T.E., Dowling, T.P.F., Stokes, C.R., Hugenholtz, C.G.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2016
• Subjects: Ice Sheet
• Online Access: http://dro.dur.ac.uk/19256/; http://dro.dur.ac.uk/19256/1/19256.pdf; http://dro.dur.ac.uk/19256/2/19256.pdf; https://doi.org/10.1002/2016GL069558

Subglacial bedforms (drumlins, ribbed moraines, mega-scale glacial lineations) are enigmatic repetitive flow-parallel and flow-transverse landforms common in glaciated landscapes. Their evolution and morphology are a potentially powerful constraint for ice sheet modelling, but there is little consensus on bedform dynamics or formative mechanisms. Here we explore shallow sediment bedform dynamics via a simple model that iterates: (i) down-flow till flux, (ii) pressure gradient driven till flux, and (iii) entrainment and deposition of sediment. Under various boundary conditions, replicas of subglacial bedforms readily emerge. Bedform dynamics mirror those in subaqueous and aeolian domains. Transitions between ribbed moraines and elongate flow-parallel bedforms are associated with increasing ice speeds and declining sediment thickness. These simulations provide quantitative flux estimates and suggest that widely observed transitions in shallow sediment subglacial bedforms (e.g., ribbed moraines to drumlinoids to mega-scale glacial lineations) are manifestations of subtle variations in ice velocity and sediment thickness.