Persistence and variability of ice-stream grounding lines on retrograde bed slopes

• Main Authors: A. A. Robel, C. Schoof, E. Tziperman
• Format: Article
• Language: English
• Published: Copernicus Publications 2016-08-01
• Series: The Cryosphere
• Online Access: http://www.the-cryosphere.net/10/1883/2016/tc-10-1883-2016.pdf

In many ice streams, basal resistance varies in space and time due to the dynamically evolving properties of subglacial till. These variations can cause internally generated oscillations in ice-stream flow. However, the potential for such variations in basal properties is not considered by conventional theories of grounding-line stability on retrograde bed slopes, which assume that bed properties are static in time. Using a flow-line model, we show how internally generated, transient variations in ice-stream state interact with retrograde bed slopes. In contrast to predictions from the theory of the marine ice-sheet instability, our simulated grounding line is able to persist and reverse direction of migration on a retrograde bed when undergoing oscillations in the grounding-line position. In turn, the presence of a retrograde bed may also suppress or reduce the amplitude of internal oscillations in ice-stream state. We explore the physical mechanisms responsible for these behaviors and discuss the implications for observed grounding-line migration in West Antarctica.