|Title||Episodic ice velocity fluctuations triggered by a subglacial flood in West Antarctica|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Siegfried M.R, Fricker H.A, Carter S.P, Tulaczyk S.|
|Journal||Geophysical Research Letters|
|Type of Article||Article|
|Keywords||antarctica; basal shear-stress; beneath; glacier; glaciology; ice dynamics; Ice sheet; lakes; sheet; stagnation; streams; subglacial; subglacial hydrology; system; water-piracy; whillans|
Height change anomalies in satellite altimeter data have been interpreted as the surface expressions of basal water moving into and out of subglacial lakes. These signals have been mapped throughout Antarctica on timescales of months to years, but only broad connections have been made between active lakes and ice dynamics. We present the first high-frequency observations of ice velocity evolution due to a cascading subglacial lake drainage event, collected over 5 years (2010-2015) using Global Positioning System data on Whillans and Mercer ice streams, West Antarctica. We observed three episodic ice velocity changes over 2 years, where flow speed increased by up to 4%, as well as an 11-month disruption of the tidally modulated stick-slip cycle that dominates regional ice motion. Our observations reveal that basal conditions of an Antarctic ice stream can rapidly evolve and drive a dynamic ice response on subannual timescales, which can bias observations used to infer long-term ice sheet changes.
We have used 5 years of continuous GPS data from stations located on and between lakes on WIS/MIS to suggest that subglacial activity does affect ice dynamics. In one of the few regions of Antarctica where ice velocity is decelerating, a subglacial flood coincided with a sustained, 2 year period of enhanced ice flow of large enough magnitude to reverse the regional slowdown. During this event, normal stick-slip behavior was also interrupted, which was associated with reduced shear strain rates. As shear strain rates began increasing toward background levels, normal stick-slip timing was restored within days. This normal state persisted even though the basal hydrology system continued to evolve and drive even higher compressive strain rates, highlighting the complexity between inland transmission of stresses, basal dynamics, and subglacial hydrology.