Raymond Effect
Raymond Effect is a flow effect in ice sheets, occurring at flow divides, which gives rise to disturbances in the stratigraphy, showing unusual arches or anticlines called Raymond Arches.[1] The stratigraphy is detected by radio-echo sounding. The Raymond effect arises from the unusual flow properties of ice, as its viscosity decreases with stress. [2] It is of importance because it provides field evidence for the flow properties of ice .[3] In addition, it permits dating of changes in ice flow and the establishment of changes in ice thickness.[4] The effect was first predicted by Charles F. Raymond.[5] Raymond Arches and the Raymond Effect have been observed at numerous other ice divides e.g. Siple Dome ,[6] Fletcher Ice Rise, Berkner Island,[7][8] , Roosevelt Island ,[4][8] Korff Ice Rise. [9]
Ice viscosity is stress-dependent, and in zones where the (deviatoric) stresses are low, the viscosity becomes very high. Near the base of ice-sheets, stress is proportional to the surface slope, at least when averaged over a suitable horizontal distance. At the flow divide, the surface slope is zero, and calculations show that the viscosity increases.[5] This diverts ice flow laterally, and is the cause of the characteristic anticlines, which are in effect draped over the high viscosity area.
References
- ^ Vaughan, David G.; Hugh F. J. Corr; Christopher S. M. Doake; Ed. D. Waddington (25 March 1999). "Distortion of isochronous layers in ice revealed by ground-penetrating radar". Nature. 398 (6725): 323–326. doi:10.1038/18653.
- ^ Glen, J.W. (1955). "The creep of polycrystalline ice". Proceedings of the Royal Society. A228 (1175): 519–538. doi:10.1098/rspa.1955.0066.
- ^ Gillet-Chaulet, F.; et al. (2011). "In-situ quantification of ice rheology and direct measurement of the Raymond Effect at Summit, Greenland using a phase-sensitive radar". Geophysical Research Letters. 38. doi:10.1029/2011GL049843.
- ^ a b Conway, H.; B. Hall; G. Denton; A. Gades; E.D. Waddington (1999). "Past and future grounding-line retreat of the West Antarctic Ice". Science. 286 (5438): 280–283. doi:10.1126/science.286.5438.280. PMID 10514369.
- ^ a b Raymond C.F. (1983). "Deformation in the vicinity of ice divides". Journal of Glaciology. 29 (103): 357–373. doi:10.1017/S0022143000030288.
- ^ Nereson, N.A.; Raymond, C.F.; et al. (2000). "The accumulation pattern across Siple Dome, West Antarctica, inferred from radar-detected internal layers". Journal of Glaciology. 46 (152): 75–87. doi:10.3189/172756500781833449.
- ^ Hindmarsh, R.C.A.; King, E.C.; Mulvaney, R.; et al. (2011). "Flow at ice-divide triple junctions: 2. Three-dimensional views of isochrone architecture from ice-penetrating radar surveys". Journal of Geophysical Research. 116 (F02024). doi:10.1029/2010JF001785. Retrieved 19 August 2020.
- ^ a b Kingslake, J.; Hindmarsh, R.C.A; Aðalgeirsdóttir, G.; et al. (2014). "Full-depth englacial vertical ice-sheet velocities measured using phase-sensitive radar". Journal of Geophysical Research. 119. doi:10.1029/2014JF003275.
- ^ Kingslake, J.; Martín, C.; et al. (2016). "Ice‐flow reorganization in West Antarctica 2.5 kyr ago dated using radar‐derived englacial flow velocities". Geophysical Research Letters. 43 (17): 9103–9112. doi:10.1002/2016GL070278.
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