Stress coupling between supraglacial lakes during rapid drainage

Abstract

<p>Greenland supraglacial lakes sometimes drain to the ice-sheet base only hours to days apart in time, leading to the hypothesis that stress transmission following one drainage may be sufficient to induce hydro-fracture-driven drainages of other lakes. However, available observations characterizing the time- and length-scales of drainage-induced stress perturbations are insufficient to evaluate this hypothesis, hindering our understanding of whether lower-elevation lake drainages could generate stress changes that initiate hydro-fracture beneath lakes in inland ice-sheet regions. Here, we invert ice-sheet surface displacement observations from a dense Global Positioning System (GPS) array deployed around three supraglacial lakes in the Greenland Ice Sheet ablation zone to estimate the space-time history of slip and opening along pre-defined planes within an elastic half-space that best reproduces GPS observations during two rapid drainage events. We then use these slip and opening estimates to forward model ice-sheet surface stresses across all three neighboring lake basins and investigate stress transmission between the basins. We find that drainage of a central lake places neighboring basins in either tensional or compressional surface stress relative to their individual hydro-fracture scarp orientations, which, respectively, promotes or inhibits hydro-fracture initiation beneath those lakes. Surface-stress-change direction is asymmetric across the lake-draining fracture of the central lake and highly dependent on where surface uplift occurs. On elastic timescales, lake-drainage-induced stresses within the extent of the GPS array in the inland direction remain low within ~3 km of the central lake. This short length-scale for stress coupling in the inland direction is consistent with idealized lake-drainage scenarios for different lake volumes and ice-sheet thicknesses. Our observations and idealized-model results support the stress-transmission hypothesis for inducing hydro-fracture-driven drainage of lakes located within the region of uplift produced by the initial drainage, but refute this hypothesis for distal lakes not located down the subglacial hydraulic catchment from the initial drainage.</p>