title: Greenland supraglacial lake drainages triggered by hydrologically induced basal slip.
abstract: Water-driven fracture propagation beneath supraglacial lakes rapidly transports large volumes of surface meltwater to the base of the Greenland Ice Sheet. These drainage events drive transient ice-sheet acceleration and establish conduits for additional surface-to-bed meltwater transport for the remainder of the melt season. Although it is well established that cracks must remain water-filled to propagate to the bed, the precise mechanisms that initiate hydro-fracture events beneath lakes are unknown. Here we show that, for a lake on the western Greenland Ice Sheet, drainage events are preceded by a 6-12 hour period of ice-sheet uplift and/or enhanced basal slip. Our observations from a dense Global Positioning System (GPS) network allow us to determine the distribution of meltwater at the ice-sheet bed before, during, and after three rapid drainages in 2011-2013, each of which generates tensile stresses that promote hydro-fracture beneath the lake. We hypothesize that these precursors are associated with the introduction of meltwater to the bed through neighbouring moulin systems (vertical conduits connecting the surface and base of the ice sheet). Our results imply that as lakes form in less crevassed, interior regions of the ice sheet, where water at the bed is currently less pervasive, the creation of new surface-to-bed conduits caused by lake-draining hydro-fractures may be limited.
authors.affiliation: Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, Woods Hole, Massachusetts 02543, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Stevens
authors.affiliation: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Behn
authors.affiliation: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: McGuire
authors.affiliation: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Das
authors.affiliation: Polar Science Center, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105-6698, USA.
authors.forename: Ian
authors.initials: I
authors.lastname: Joughin
authors.affiliation: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Herring
authors.affiliation: Polar Science Center, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105-6698, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Shean
authors.affiliation: 1] School of Land and Food, University of Tasmania, Private Bag 76, Hobart, Tasmania 7001, Australia [2] School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Matt A
authors.initials: MA
authors.lastname: King