The presence of water flowing beneath the Greenland Ice Sheet impacts the friction exerted on ice flowing from inland to marginal regions, potentially affecting the rate of sea level rise by increasing ice discharge. Direct observations of the hydrological system beneath glaciers are, however, limited due to inaccessibility. Here, we present satellite observations of localized ice uplift and subsidence, which indicate water propagating below the Northeast Greenland Ice Stream, from far inland to a major marine-terminating glacier, Zachariae Isstrøm. In downstream regions, ice flow speeds up as the subglacial water passes. The measurements could suggest variations in the local subglacial environment, which provide important constraints for understanding the flow and stability of the ice stream.

Abstract

Subglacial hydrology can exert an important control on ice flow by affecting friction at the ice-bedrock interface. Here, we report on a series of subglacial drainage events along the Northeast Greenland Ice Stream (NEGIS), initiating as far inland as 500 km from the margin of Zachariae Isstrøm. The drainage events exhibit local transient uplift, followed by prolonged subsidence, measured by differential satellite synthetic aperture radar interferometry (DInSAR). In downstream regions, drainage events are associated with temporary acceleration in ice flow. The high spatiotemporal resolution of the DInSAR measurements allows for a detailed mapping of the drainage propagation pathway. We show that multiple drainage cascades have occurred along the same pathway over the years 2020–2022. Finally, the propagation speed of subglacial water flow is found to vary greatly along NEGIS, suggesting that fundamental differences could exist in the subglacial environment.

Key points

  • Episodic subglacial drainage of water over a ∼500 km extent along the Northeast Greenland Ice Stream is revealed by radar interferometry
  • The drainage events cause transient uplift and ice flow speed-up in downstream regions, and multiple drainage cascades are observed
  • Propagation speed of the drainage cascade varies widely along the ice stream

Timelapse of a drainage event