Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage

TLDR

Surface meltwater reaching the base of an ice sheet creates a mechanism for rapid ice‑flow response to climate change, yet the formation of such a pathway through thick, cold ice has not been previously observed. A large supraglacial lake drained in under two hours down 980 m to the Greenland Ice Sheet bed, producing seismicity, transient acceleration, uplift, and horizontal displacement, followed by subsidence and deceleration over 24 h, showing that efficient drainage disperses meltwater subglacially and that repeated events could explain regional summer ice speedup.

Abstract

Surface meltwater that reaches the base of an ice sheet creates a mechanism for the rapid response of ice flow to climate change. The process whereby such a pathway is created through thick, cold ice has not, however, been previously observed. We describe the rapid (<2 hours) drainage of a large supraglacial lake down 980 meters through to the bed of the Greenland Ice Sheet initiated by water-driven fracture propagation evolving into moulin flow. Drainage coincided with increased seismicity, transient acceleration, ice-sheet uplift, and horizontal displacement. Subsidence and deceleration occurred over the subsequent 24 hours. The short-lived dynamic response suggests that an efficient drainage system dispersed the meltwater subglacially. The integrated effect of multiple lake drainages could explain the observed net regional summer ice speedup.