Tidally controlled stick-slip discharge of aWest Antarctic Ice

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. Flow of an Antarctic ice stream abruptly waxes and wanes in response to daily tides, implying that the forces pushing and resisting it are delicately balanced. Flow of an Antarctic ice stream abruptly waxes and wanes in response to daily tides, implying that the forces pushing and resisting it are delicately balanced.