The formation of grounding zone wedges: theory and experiments

Kowal, K. N. and Worster, M. G. (2020) The formation of grounding zone wedges: theory and experiments. Journal of Fluid Mechanics, 898, A12. (doi: 10.1017/jfm.2020.393)

Abstract

We present a fluid-mechanical explanation of the formation of sedimentary wedges deposited at ice-stream grounding zones. We model both ice and till as layers of viscous fluid spreading under gravity into an inviscid ocean. To test the fundamentals of our theory, we perform a series of laboratory experiments in which we find that a similar wedge of underlying, less viscous fluid accumulates spontaneously around the grounding line. We formulate a simple local condition relating wedge slopes, which determines wedge geometry. It expresses a balance of fluxes of till either side of the grounding line and involves upstream and downstream gradients of till thicknesses as well as the upper surface gradient of the ice. It shows that a wedge will form, that is the upstream till thickness gradients are positive, when the flux of till driven by the glaciostatic pressure gradient of the overlying ice is greater than the flux of till ahead of the grounding zone. This is related to the unloading of the till as the ice sheet crosses the grounding line.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kowal, Dr Katarzyna
• Authors: Kowal, K. N., and Worster, M. G.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Journal of Fluid Mechanics
• Publisher: Cambridge University Press
• ISSN: 0022-1120
• ISSN (Online): 1469-7645
• Published Online: 03 July 2020
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in Journal of Fluid Mechanics 898:A12
• Publisher Policy: Reproduced under a Creative Commons licence