Rapid subglacial water system evolution triggered by subglacial floods in West Antarctica

Abstract:

Water at the ice-bed interface controls the rate at which Antarctica’s glaciers and ice streams flow towards the ocean, but a calibrated, quantitative link between ice flow and subglacial hydrology remains elusive, largely due to a lack of suitable observations. Active subglacial lakes, which fill and drain on sub-decadal timescales, can be indirectly observed via surface displacements. On ice streams, these lakes potentially alter ice motion by sequestering and episodically releasing up to cubic kilometers of subglacial meltwater generated in the upstream catchment. Here, we use five years (2010-2015) of continuous Global Positioning System (GPS) data on the Whillans and Mercer ice streams, West Antarctica, to observe cascading subglacial floods and their impact on ice flow. These connected events caused two years of enhanced ice flow, with episodic velocity fluctuations of nearly 4% correlated to lake drainage evolution, and an eleven-month disruption of the tidally-paced stick-slip cycle that dominates regional ice motion. Our continuous, long-term observations allow assessment of inherent dynamic ice-stream variability and indicate that episodic processes may bias typical campaign-style observations. Unbiased observations of coupled subglacial-glacial dynamics are fundamental for understanding past and future ice sheet evolution as subglacial hydrological processes likely control large-scale oscillations of ice-stream motion.