Abstract
Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed. Here we use a well-constrained 3D model to demonstrate that supraglacial lakes in Greenland drain when tensile-stress perturbations propagate fractures in areas where fractures are normally absent or closed. These melt-induced perturbations escalate when lakes as far as 80 km apart form expansive networks and drain in rapid succession. The result is a tensile shock that establishes new surface-to-bed hydraulic pathways in areas where crevasses transiently open. We show evidence for open crevasses 135 km inland from the ice margin, which is much farther inland than previously considered possible. We hypothesise that inland expansion of lakes will deliver water and heat to isolated regions of the ice sheet’s interior where the impact on ice flow is potentially large.
Highlights
Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed
The latter was coupled to a 5-mthick layer of soft basal till, which is a glacially produced sediment observed beneath the ice sheet in this region[24,25,26] including lake sites[26]
The total runoff produced by surface melting in 2010 was 6.58 km[3] and considerably higher than the amount of water stored in supraglacial lakes (SGLs), we focus on the latter because previous work found lake drainages to induce short-lived but sustained episodes of ice flow acceleration, consistent with the observed seasonal variation of ice flow in this[11] and other sectors[8] of the Greenland Ice Sheet
Summary
Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed. We use a well-constrained 3D model to demonstrate that supraglacial lakes in Greenland drain when tensile-stress perturbations propagate fractures in areas where fractures are normally absent or closed These melt-induced perturbations escalate when lakes as far as 80 km apart form expansive networks and drain in rapid succession. We show that distinct events, with up to 124 lakes draining over the course of a few days, occur when basal lubrication along subglacial drainage paths transiently induces highmagnitude tensile stresses near the surface This ephemeral and previously overlooked alteration of the ice sheet’s force balance escalates into a tensile shock when many lakes drain collectively in a chain reaction. We use cascading lake drainage to describe the latter and show that most lakes drain in this dynamic manner
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