Towards a description of stick-slip motion using a viscoelastic Full Stokes model 

Abstract

<p>The lightly grounded portion of the Whillans Ice Stream (WIS, Siple Coast, Antarctica), has a unique stick-slip motion behaviour, where prolonged stagnant phases (6-25 hrs) are interrupted by rapid active slip events (up to 0.5 m in < 1 hr).  WIS is also interesting because it is currently stagnating, presenting an important opportunity to understand this behaviour and its effect on future sea level rise. Detailed observations and a variety of modelling approaches have revealed the complexity of stick-slip behaviour and the importance of correctly representing ice rheology, ice stream geometry, spatial variability of friction strength, and boundary conditions. Currently, no single model exists that can fully replicate all the observed features of stick-slip motion as observed on the Whillans Ice Plain. Here we describe a full-Stokes viscoelastic finite element model that has been previously used to explore tidal modulation of ice stream flow, and which can overcome some of the assumptions adopted in previous work. The model is  set up for an idealised configuration of the Whillans Ice Plain, with the aim of exploring how the inclusion of relevant additional physics affects stick-slip motion for a rate and state friction law, and whether other sliding laws could also explain the observed motion. Ultimately, this modelling work aims to put tighter constraints on the conditions required to initiate stick-slip behaviour, improving our understanding of basal sliding and future sea level rise.</p>