New metrics reveal the evolutionary continuum behind the morphological diversity of subglacial bedforms

• Published in: Geomorphology
• Main Authors: Vérité, Jean, Ravier, Édouard, Bourgeois, Olivier, Bessin, Paul, Pochat, Stéphane
• Other Authors: Laboratoire de Planétologie et Géosciences - Le Mans (LPG - Le Mans), Laboratoire de Planétologie et Géosciences UMR_C 6112 (LPG), Le Mans Université (UM)-Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Le Mans Université (UM)-Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), ANR-18-CE01-0009,Ice-Collapse,Dynamique d'éffondrement d'une calotte glaciaire en période de déglaciation(2018)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Glacial geomorphology; Ribbed bedforms; Drumlins; MSGLs; Continuum; Sinuous forms; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; Ice Sheet
• Online Access: https://hal.science/hal-04329984; https://hal.science/hal-04329984/document; https://hal.science/hal-04329984/file/Vritetal.2023-Newmetricsrevealtheevolutionarycontinuumbehindthemorphologicaldiversityofsubglacialbedforms.pdf; https://doi.org/10.1016/j.geomorph.2023.108627

Understanding the formation of subglacial bedforms is primordial to constrain ice-meltwater-bed interactions and the dynamics of past and present ice sheets. However, the difficulty to observe active subglacial bedforms below present-day ice sheets implies that their formation and evolution are essentially deduced from the inversion of morphological and sedimentological data from palaeo-subglacial bedforms. In this study, the morphological characteristics of subglacial bedforms are explored with a new approach based on the combination of three dimensionless morphometric indices i.e., circularity index, sinuosity index and elongation component ratio. We measure the spatial distribution of these indices on an unpublished database composed of ~13,500 digitized bedforms taken from two selected portions of the Irish Ice Sheet and Laurentide Ice Sheet beds considering that (1) all subglacial bedforms in each region were formed under a single ice flow configuration and (2) the bedforms may have developed either orthogonal, parallel, or oblique to ice displacement directions. Our results reveal a morphometric and spatial continuum along which ribbed bedforms of various lengths and shapes – ranging from circular to elongated flow-transverse forms – are incipient bedforms that can evolve into transitional sinuous ribbed bedforms, then into predominantly flow-parallel sinuous bedforms that progressively realign to form streamlined bedforms. Assuming the glaciological contexts of selected study areas, this continuum may provide a new geomorphic criterion to constrain spatial variations in subglacial conditions (e.g. ice flow velocity, bedrock characteristics, meltwater pressure).