Tidally Controlled Stick-Slip Discharge of a West Antarctic Ice

Abstract

A major West Antarctic ice stream discharges by sudden and brief periods of very rapid motion paced by oceanic tidal oscillations of about 1 meter. Acceleration to speeds greater than 1 meter per hour and deceleration back to a stationary state occur in minutes or less. Slip propagates at approximately 88 meters per second, suggestive of a shear wave traveling within the subglacial till. A model of an episodically slipping friction-locked fault reproduces the observed quasi-periodic event timing, demonstrating an ice stream's ability to change speed rapidly and its extreme sensitivity to subglacial conditions and variations in sea level.

Diurnal and semidiurnal tide‐induced lateral movement of Ronne Ice Shelf, Antarctica

“…On RIS, which experiences the largest tidal range around Antarctica of up to 7 m, the oscillations in velocity and strain are much larger than on smaller ice shelves. The oscillating ice shelf stresses, which will be zero at the ice front and greatest toward grounding lines, will influence the horizontal force balance of the inflowing ice streams and the phase relationship between ice stream flow and the tidal forcing, particularly ice streams with low-friction beds [e.g., Anandakrishnan et al, 2003;Bindschadler et al, 2003;Thomas, 2007]. For parts of RIS where its length exceeds 600 km and the thickness ranges from 300 m at the ice front, to over 1200 m at the grounding lines, the horizontal elastic stresses could exceed AE20 kPa, which is approaching the stress perturbations caused by the tidally varying height of the water column.…”

Tremor during ice-stream stick slip

“…Ocean tides in the Ross sea feature a strong diurnal component, and the timing of slip events is nearly synchronous with the high and low ocean tides (Bindschadler et al, 2003). Skipped events are usually low tide events, with the subsequent slip event occurring at high tide.…”

“…4 km 2 ice plain undergoes tidally modulated onceor twice-daily stick-slip motions (Bindschadler et al, 2003;Wiens et al, 2008). During the time between large-scale sliding events, several ∼100 km 2 regions exhibit a high degree of locking (Winberry et al, 2014c).…”

Continued deceleration of Whillans Ice Stream, West Antarctica

“…While stuck, elastic strain builds between the ''stuck'' area and the still rapidly flowing upstream region [Bindschadler et al, 2003b]. The ice shelf's tidally driven displacement just seaward of the grounding line also contributes to the ice stream's force balance.…”