Isolated Cavities Dominate Greenland Ice Sheet Dynamic Response to Lake Drainage

Seasonal variability in the Greenland Ice Sheet's (GrIS) sliding speed is regulated by the response of the subglacial drainage system to meltwater inputs. However, the importance of channelization relative to the dewatering of isolated cavities in controlling seasonal ice deceleration remains unsolved. Using ice motion, moulin hydraulic head, and glaciohydraulic tremor measurements, we show the passing of a subglacial floodwave triggered by upglacier supraglacial lake drainages slowed sliding to wintertime background speeds without increasing the hydraulic capacity of the moulin-connected drainage system. We interpret these results to reflect an increase in basal traction caused by the dewatering of isolated cavities. These results suggest the dewatering of isolated parts of the subglacial drainage system play a key role in driving seasonal slowdowns on the GrIS.

Automated summary

Seasonal variability in Greenland Ice Sheet's sliding speed is mainly regulated by the response of the subglacial drainage system to meltwater inputs. Analysis of measurements shows that the dewatering of isolated cavities leads to an increase in basal traction, causing the ice deceleration. Therefore, the dewatering of isolated parts of the subglacial drainage system plays a key role in driving seasonal slowdowns on the Greenland Ice Sheet.