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[1] called Raymond Arches. The stratigraphy is detected by radio-echo sounding. The Raymond effect arises from the unusual flow properties of ice. It is of importance because it provides field evidence for the flow properties of ice [2] . In addition, it permits dating of changes in ice flow and the establishment of changes in ice thickness.[3] The effect was first predicted by Charles F. Raymond.[4]

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[4]. This diverts ice flow laterally, and is the cause of the characteristic anticlines, which are in effect draped over the high viscosity area.

References
  1. 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.
  2. 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.
  3. 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.
  4. Raymond C.R. (1983). "Deformation in the vicinity of ice divides". Journal of Glaciology. 29 (103): 357–373. doi:10.1017/S0022143000030288.


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