title: Ice stream motion facilitated by a shallow-deforming and accreting bed.
abstract: Ice streams drain large portions of ice sheets and play a fundamental role in governing their response to atmospheric and oceanic forcing, with implications for sea-level change. The mechanisms that generate ice stream flow remain elusive. Basal sliding and/or bed deformation have been hypothesized, but ice stream beds are largely inaccessible. Here we present a comprehensive, multi-scale study of the internal structure of mega-scale glacial lineations (MSGLs) formed at the bed of a palaeo ice stream. Analyses were undertaken at macro- and microscales, using multiple techniques including X-ray tomography, thin sections and ground penetrating radar (GPR) acquisitions. Results reveal homogeneity in stratigraphy, kinematics, granulometry and petrography. The consistency of the physical and geological properties demonstrates a continuously accreting, shallow-deforming, bed and invariant basal conditions. This implies that ice stream basal motion on soft sediment beds during MSGL formation is accommodated by plastic deformation, facilitated by continuous sediment supply and an inefficient drainage system.
authors.affiliation: Department of Geography and Environment, School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen AB243UF, UK.
authors.forename: Matteo
authors.initials: M
authors.lastname: Spagnolo
authors.affiliation: British Geological Survey, Edinburgh EH93LA, UK.
authors.forename: Emrys
authors.initials: E
authors.lastname: Phillips
authors.affiliation: Department of Geoscience, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Jan A
authors.initials: JA
authors.lastname: Piotrowski
authors.affiliation: Department of Geography and Environment, School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen AB243UF, UK.
authors.forename: Brice R
authors.initials: BR
authors.lastname: Rea
authors.affiliation: Department of Geography, University of Sheffield, Sheffield S102TN, UK.
authors.forename: Chris D
authors.initials: CD
authors.lastname: Clark
authors.affiliation: Department of Geography, Durham University, Durham DH13LE, UK.
authors.forename: Chris R
authors.initials: CR
authors.lastname: Stokes
authors.affiliation: School of Geography, Queen Mary University of London, London E14NS, UK.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Carr
authors.affiliation: Department of Geography, University of Sheffield, Sheffield S102TN, UK.
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Ely
authors.affiliation: Dipartimento di Scienze della Terra, University of Pisa, 56126 Pisa, Italy.
authors.forename: Adriano
authors.initials: A
authors.lastname: Ribolini
authors.affiliation: Faculty of Earth Sciences, Nicolaus Copernicus University, 87-100 Toruń, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Wysota
authors.affiliation: Department of Geomorphology, Adam Mickiewicz University, Poznan 61-680, Poland.
authors.forename: Izabela
authors.initials: I
authors.lastname: Szuman