Flow dynamics of the Whillans Ice Stream, West Antarctica: Implications for basal mechanics and subglacial hydrology

The Whillans Ice Stream (WIS) is a fast flow feature of the West Antarctic Ice Sheet and is an important conduit for the discharge of ice into the ocean. It is known that the dynamics of the WIS is variable on numerous time scales between daily and decadally. WIS is slowing down at an increasingly fast rate, with maximum observed deceleration, 6.1 to 10.9 +/- 2 m/yr2, occurring during 2009 - 2013. Deceleration of the ice stream can be explained by increases in basal resistance of 10 to 40 Pa/yr. Which may be the result of basal hydrological or thermodynamic processes, such as gradual drying of the subglacial till through basal freeze-on or subglacial hydrology geometry change.;Subglacial hydrology, including the filling and draining of active subglacial lakes cause modification of basal effective pressure and resulting velocity anomalies. These changes are super imposed over the longer term deceleration trend. Five filling and draining events captured between December 2007 and October 2013, show variable sensitivity of ice flow to hydrological activity that might be related to location of the ice stream and the distribution of basal resistance magnitude.;In each case small changes in basal resistance of 10s Pa/yr are sufficient to cause changes in the rate of ice motion. These changes, both positive and negative, depending on the forcing processes respond to subtile changes in basal effective pressure and distribution of water.;The ice stream is a sensitive system that has numerous internal therm-dynamic feedbacks. How the subglacial sediments characteristics, including water content and void ratio evolve, are seen a critical to describe the changes in WIS motion over time scales varying from decades to weeks or shorter.