title: Greenland subglacial drainage evolution regulated by weakly connected regions of the bed.
abstract: Penetration of surface meltwater to the bed of the Greenland Ice Sheet each summer causes an initial increase in ice speed due to elevated basal water pressure, followed by slowdown in late summer that continues into fall and winter. While this seasonal pattern is commonly explained by an evolution of the subglacial drainage system from an inefficient distributed to efficient channelized configuration, mounting evidence indicates that subglacial channels are unable to explain important aspects of hydrodynamic coupling in late summer and fall. Here we use numerical models of subglacial drainage and ice flow to show that limited, gradual leakage of water and lowering of water pressure in weakly connected regions of the bed can explain the dominant features in late and post melt season ice dynamics. These results suggest that a third weakly connected drainage component should be included in the conceptual model of subglacial hydrology.
authors.affiliation: Fluid Dynamics and Solid Mechanics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Matthew J
authors.identifier: 0000-0001-5076-0540
authors.initials: MJ
authors.lastname: Hoffman
authors.affiliation: Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Andrews
authors.affiliation: Fluid Dynamics and Solid Mechanics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Price
authors.affiliation: Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78758, USA.|Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78758, USA.
authors.forename: Ginny A
authors.initials: GA
authors.lastname: Catania
authors.affiliation: Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Neumann
authors.affiliation: Glaciology and Geomorphodynamics Group, Department of Geography, University of Zürich, 8057 Zürich, Switzerland.
authors.forename: Martin P
authors.initials: MP
authors.lastname: Lüthi
authors.affiliation: School of Geosciences, University of South Florida, Tampa, Florida 33620, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Gulley
authors.affiliation: Laboratory of Hydraulics, Hydrology and Glaciology, Swiss Federal Institute of Technology (ETH) Zürich, 8093 Zürich, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Ryser
authors.affiliation: Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Hawley
authors.affiliation: Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755, USA.
authors.forename: Blaine
authors.initials: B
authors.lastname: Morriss