Subglacial lake drainage event impacts basal hydrology and dynamics of Greenland outlet glacier

Subglacial lakes are important hydrological reservoirs within the Greenland Ice Sheet, primarily fed by meltwater from the surface that reaches the bed. Episodically, these lakes drain, releasing vast volumes of water into the subglacial drainage system and thereby altering basal hydrology and local ice dynamics. A warming climate is expected to intensify surface meltwater production and potentially increase the frequency of subglacial lake drainage events. However, direct observations of such events remain scarce, limiting our understanding of their driving mechanisms and impacts on the subglacial system.

 

Here we document a subglacial lake at Eqalorutsit Kangilliit Sermiat, a major tidewater outlet glacier in Southwest Greenland. This subglacial lake typically drains once or twice per melt season. We observed one such event using time-lapse imagery, GNSS measurements, terrestrial radar interferometry, and digital elevation models (DEMs). From these observations, we estimate a drainage volume of approximately 0.3 km³, and local ice surface lowering that exceeds 50 m. Additionally, we delineated the lake outline and were able to estimate lake drainage rates and refilling rates. Our results further indicate a (partial) re-routing of the subglacial drainage system following the lake drainage event. As the lake drained, we observed an acceleration of the glacier’s terminus region and the emergence of a large sediment-rich plume. This highlights the profound influence of episodic subglacial lake drainage on glacier dynamics as well as fjord circulation and ecosystems.