Abstract
AbstractWe present a mathematical model of the hydrology of grounding‐line migration on tidal timescales, in which the ice acts elastically, overlying a connected hydrological network, with the ocean tides modeled by an oscillating far‐field fluid height. The upstream grounding‐line migration is driven by a fluid pressure gradient through the grounding zone, while the downstream migration is limited by fluid drainage through the till. The two processes are described using separate travelling‐wave solutions, based on a model of fluid flow under an elastic sheet. The asymmetry between the upstream and downstream motion allows the grounding line to act as a nonlinear filter on the tidal forcing as the pressure signal propagates upstream, and this frequency modulation is discussed in the context of velocity data from ice streams across Antarctica to provide a novel constraint on till permeability.
Highlights
The grounding zone of an ice sheet represents the region over which the ice ceases to be supported by the bed and forms an ice shelf floating over the ocean
We present a mathematical model of the hydrology of grounding-line migration on tidal timescales, in which the ice acts elastically, overlying a connected hydrological network, with the ocean tides modeled by an oscillating far-field fluid height
The asymmetry between the upstream and downstream motion allows the grounding line to act as a nonlinear filter on the tidal forcing as the pressure signal propagates upstream, and this frequency modulation is discussed in the context of velocity data from ice streams across Antarctica to provide a novel constraint on till permeability
Summary
The grounding zone of an ice sheet represents the region over which the ice ceases to be supported by the bed and forms an ice shelf floating over the ocean. To generate a 14-day frequency in the surface, velocity from daily tides requires a nonlinear mechanism to act between the tidal forcing and velocity response (Rosier et al, 2015). Rosier and Gudmundsson (2020) demonstrated that tidal variations in basal traction at the grounding line are a dominant factor in determining the large scale velocity of marine ice sheets, suggesting the need to accurately assess lubrication by subglacial water across the grounding zone. Tsai and Gudmundsson (2015) considered the impact of variable ice thickness on the static equilibrium position of the grounding line and proposed a fracture-mechanics model for the incoming tide. By studying the dynamics of water transport across the grounding line over the tidal cycle, we describe a self-consistent mechanism coupling the grounding-line migration and subglacial hydrology
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