Stick–slip behavior of ice streams: modeling investigations

Abstract

A puzzling phenomenon of ice-stream flow is the stick–slip motion displayed by Whillans Ice Stream (WIS), West Antarctica. In this study we test the hypothesis that the WIS stick–slip motion has features similar to those of other known stick–slip systems, and thus might be of the same origin. To do so, we adapt a simple mechanical model widely used in seismology to study classic stick–slip behavior observed in tectonic faults, in which the difference between static and dynamic friction allows for the generation and spatial propagation of abrupt slip events. We show how spatial variability in friction properties, as well as a periodic forcing intended to mimic the effect of tides, can reproduce the observed duration and periodicity of stick–slip motion in an ice stream. An intriguing aspect of the association of WIS with mechanical stick–slip oscillators is that the onset of stick–slip cycling from a condition of permanent slip appears to be associated with the reduction in overall speed of WIS. If this association is true, then stick–slip behavior of WIS is a transitional phase of behavior associated with the ice stream's recent deceleration.

Modeling the elastic transmission of tidal stresses to great distances inland in channelized ice streams

“…Many models have been proposed to explain the influence that ocean tides have on the motion of some Antarctic ice streams (e.g., Anandakrishnan and Alley, 1997;Bindschadler et al, 2003;Gudmundsson, 2006Gudmundsson, , 2007Gudmundsson, , 2011Sergienko et al, 2009;Walker et al, 2012;Winberry et al, 2009). Given that the Maxwell relaxation time (viscosity / elastic modulus) for ice is on the order of a few hours for tidal loads, these models generally model either elastic or viscoelastic transmission of ocean tidal stresses through the ice stream inland of the grounding line -referred to as "stress transmission" in this manuscript.…”

Tremor during ice-stream stick slip

“…A description such as Eq. (15) may be thought of as a refinement to the generally accepted frictional-plastic rheological description of till (Tulaczyk et al, 2000) and as generalization of a frictional model consisting only of static and dynamic coefficients of friction (e.g., Sergienko et al, 2009). …”

Insights into ice stream dynamics through modelling their response to tidal forcing

“…The next step was the realisation that horizontal ice stream velocities could be modulated by the tides; much of the initial work focused on the Whillans ice stream (WIS) which was shown to exhibit a stick-slip behaviour resulting from vertical ocean tides (Anandakrishnan et al, 2003;Bindschadler et al, 2003b, a;Wiens et al, 2008;Winberry et al, 2009;Sergienko et al, 2009). This ice stream has mean annual speeds of greater than 300 m a −1 , but the majority of motion occurs in brief bursts over timescales less than 1 h followed by longer periods where the ice is almost stationary.…”