50 research outputs found
Conceptual model for the formation of bedforms along subglacial meltwater corridors (SMCs) by variable iceâwaterâbed interactions
Subglacial meltwater landforms found on palaeo-ice sheet beds allow the properties of meltwater drainage to be reconstructed, informing our understanding of modern-day subglacial hydrological processes. In northern Canada and Fennoscandia, subglacial meltwater landforms are largely organized into continental-scale networks of subglacial meltwater corridors (SMCs), interpreted as the relics of subglacial drainage systems undergoing variations in meltwater input, effective pressure and drainage efficiency. We review the current state of knowledge of bedforms (hummocks, ridges, murtoos, ribbed bedforms) and associated landforms (channels, eskers) described along SMCs and use selected high-resolution DEMs in Canada and Fennoscandia to complete the bedform catalogue and categorize their characteristics, patterning and spatial distributions. We synthesize the diversity of bedform and formation processes occurring along subglacial drainage routes in a conceptual model invoking spatiotemporal changes in hydraulic connectivity, basal meltwater pressure and ice-bed coupling, which influences the evolution of subglacial processes (bed deformation, erosion, deposition) along subglacial drainage systems. When the hydraulic capacity of the subglacial drainage system is overwhelmed glaciofluvial erosion and deposition will dominate in the SMC, resulting in tracts of hummocks and ridges arising from both fragmentation of underlying pre-existing bedforms and downstream deposition of sediments in basal cavities and crevasses. Re-coupling of ice with the bed, when meltwater supply decreases, facilitates deformation, transforming existing and producing new bedforms concomitant with the wider subglacial bedform imprint. We finally establish a range of future research perspectives to improve understanding of subglacial hydrology, geomorphic processes and bedform diversity along SMCs. These perspectives include the new acquisition of remote-sensing and field-based sedimentological and geomorphological data, a better connection between the interpreted subglacial drainage configurations down corridors and the mathematical treatments studying their stability, and the quantification of the scaling, distribution and evolution of the hydraulically connected drainage system beneath present-day ice masses to test our bedform-related conceptual model
Processus de formation de bedforms triangulaires sous la paléo-calotte Scandinave : géomorphologie glaciaire et modélisation analogique
International audienc
Adrien Duport : député de Paris... : [estampe] / gravé par Verité ; dessiné d'aprÚs nature
RĂ©fĂ©rence bibliographique : De Vinck, 2098RĂ©fĂ©rence bibliographique : De Vinck, 2099RĂ©fĂ©rence bibliographique : Smith-LesouĂ«f, 13513RĂ©fĂ©rence bibliographique : VidĂ©odisque, 24785-24786Appartient Ă lâensemble documentaire : Est18Rev
Charles Fran. Bouche : député d'Aix... : [estampe] / dessiné d'aprÚs nature ; gravé par Verité
RĂ©fĂ©rence bibliographique : De Vinck, 2087RĂ©fĂ©rence bibliographique : Smith-LesouĂ«f, 13513RĂ©fĂ©rence bibliographique : VidĂ©odisque, 23110-23111Appartient Ă lâensemble documentaire : Est18Rev
Victor-Pier. Malouet : député d'Auvergne à l'Assemblée nationale... : [estampe] / dessiné d'aprÚs nature ; gravé par Verité
RĂ©fĂ©rence bibliographique : De Vinck, 2114RĂ©fĂ©rence bibliographique : Smith-LesouĂ«f, 13513RĂ©fĂ©rence bibliographique : VidĂ©odisque, 27374-27375Appartient Ă lâensemble documentaire : Est18Rev1Appartient Ă lâensemble documentaire : Auvergn
Le Duc d'Aiguillon : Député de la Sénéchaussée d'Agen... : [estampe] / Dessiné d'aprÚs nature ; Gravé par Verité
RĂ©fĂ©rence bibliographique : De Vinck, 2977RĂ©fĂ©rence bibliographique : De Vinck, 2084RĂ©fĂ©rence bibliographique : Smith-LesouĂ«f, 13513RĂ©fĂ©rence bibliographique : VidĂ©odisque, 22083-22084Appartient Ă lâensemble documentaire : Est18Rev
J.P. Marat, l'ami du peuple : second martir de la liberté... : [estampe] / dessiné d'aprÚs nature par M... ; gravé par Vérité sculp.
RĂ©fĂ©rence bibliographique : De Vinck, 5256RĂ©fĂ©rence bibliographique : Hennin, 11528RĂ©fĂ©rence bibliographique : VidĂ©odisque, 27442-27443Appartient Ă lâensemble documentaire : Est18Rev
Variations in hydraulic efficiency of the subglacial drainage landsystem control surging and streaming regimes of outlet glaciers
International audienceSurging and streaming of glaciers are modulated by meltwater availability and pressure which controls mechanical coupling at their beds. Using laboratory-scale experimental modelling and palaeoglaciological mapping, we explore how subglacial drainage landsystems control meltwater drainage efficiency and ice flow velocities for terrestrial-based ice lobes resting on flat horizontal and permeable beds. Two end-members regimes, surging and streaming, appear in our experiments. The surge regime is characterised by a rapid increase of drainage efficiency through development of tunnel valleys and their tributaries, thus reducing the duration of ice flow speed-up events by lowering water pressures and increasing ice-bed coupling. Tunnel valleys connected to ice lobe margins, submarginal thrust moraines, reduced ice lobe extensions and ephemeral shear margins are the most distinctive characteristics of this regime. The stream regime is characterised by disconnected channels of smaller dimensions unable to evacuate all the meltwater: this prolonged drainage inefficiency leads to sustained high ice flow velocity and steady shear margins. Small and rectilinear meltwater channels devoid of tributaries, often disconnected from ice lobe margins, and lineation swarms are diagnostic of this regime
Mirabeau l'aßné, député d'Aix, ex-président de l'Assemblée nationale... : il naquit au canton d'Egreville, district de Nemours, au mois de mars, 1750 et mourut à Paris le 2 avril 1791 : [estampe] / Vérité sculp.
RĂ©fĂ©rence bibliographique : De Vinck, 1885RĂ©fĂ©rence bibliographique : De Vinck, 1884RĂ©fĂ©rence bibliographique : Smith-LesouĂ«f, 13513RĂ©fĂ©rence bibliographique : VidĂ©odisque, 27955-27956Appartient Ă lâensemble documentaire : Est18Rev
L. Al. de La Rochefoucauld, : deputé de la ville de Paris, ex-président de l'Assemblée nationale, élu président du départ. de Paris... : [estampe] / dessiné d'aprÚs nature ; gravé par Verité
RĂ©fĂ©rence bibliographique : De Vinck, 2111RĂ©fĂ©rence bibliographique : Smith-LesouĂ«f, 13513RĂ©fĂ©rence bibliographique : VidĂ©odisque, 26628-26629Appartient Ă lâensemble documentaire : Est18Rev