Moulin density controls drainage development beneath the Greenland Ice Sheet

• Published in: Journal of Geophysical Research: Earth Surface
• Main Authors: Banwell, A, Hewitt, I, Willis, I, Arnold, N
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley 2016
• Subjects: Greenland; Ice Sheet
• Online Access: https://doi.org/10.1002/2015JF003801; https://ora.ox.ac.uk/objects/uuid:cfb4d484-3eb9-4b5f-9fac-c032df52d930

Uncertainty remains about how the surface hydrology of the Greenland Ice Sheet influences its subglacial drainage system, affecting basal water pressures and ice velocities, particularly over intra- and inter-seasonal timescales. Here, we apply a high spatial (200 m) and temporal (1 h) resolution subglacial hydrological model to a marginal (extending ~25 km inland), land-terminating, ~200 km^2 domain in the Paakitsoq region, West Greenland. The model is based on that by Hewitt [2013], but adapted for use with both real topographic boundary conditions and calibrated modeled water inputs [Banwell et al. 2013]. The inputs consist of moulin hydrographs, calculated by a surface routing and lake-filling/draining model, which is forced with distributed runoff from a surface energy-balance model. Results suggest that the areal density of lake-bottom moulins, and their timing of opening during the melt season, strongly affects subglacial drainage system development. A higher moulin density causes an earlier onset of subglacial channelization (i.e. water transport through channels rather than the distributed sheet), that becomes relatively widespread across the bed, whereas a lower moulin density results in a later onset of channelization that becomes less widespread across the bed. In turn, moulin density has a strong control on spatial and temporal variations in subglacial water pressures, which will influence basal sliding rates, and thus ice motion. The density of active surface-to-bed connections should be considered alongside surface melt intensity and extent in future predictions of the ice sheet’s dynamics.