The Extent of Channelized Basal Water Flow Under the Greenland Ice Sheet

Abstract:

Glacial ice flows due to a combination of deformation and basal
sliding, with sliding accounting for most of the fastest ice flow. Basal sliding is controlled by
the transport of water at the glacier's bed, which can be accomplished
through both high pressure, low discharge, distributed flow, or low
pressure, high discharge, channelized flow. Higher pressures are
generally associated with more complete decoupling of a glacier from
its bed and faster flow. As the intensity of summer melt in Greenland
has increased, our poor understanding of the drainage network's
discharge capacity and its coupling to sliding has generated
fundamental questions, such as: will larger fluxes of liquid water
promote or inhibit basal sliding? To investigate this question we have
implemented a model of distributed and channelized flow developed by
Werder et. al 2013. The sensitivity of the modeled
channel network to basal and surface geometry, melt rate,
boundary conditions, and other parameters is examined in a sequence of
experiments using synthetic geometries. Expanding on these
experiments, we run the model with realistic surface and bedrock
data from Issunguata Sermia in Western Central Greenland. These
experiments benefit from a wealth of in-situ data, including
observations of basal water pressure. Our results suggest that the
development of large channels is limited to the margins of the ice
sheet, and that higher pressures continue to prevail in the interior.