Persistent englacial drainage features in the Greenland Ice Sheet

Abstract

[1] Surface melting on the Greenland Ice Sheet is common up to $1400 m elevation and, in extreme melt years, even higher. Water produced on the ice sheet surface collects in lakes and drains over the ice sheet surface via supraglacial streams and through the ice sheet via moulins. Water delivered to the base of the ice sheet can cause uplift and enhanced sliding locally. Here we use ice-penetrating radar data to observe the effects of significant basal melting coincident with moulins and calculate how much basal melt occurred. We find that more melting has occurred than can be explained by the release of potential energy from the drainage of surface meltwater during one melt season suggesting that these moulins are persistent for multiple years. We find only a few persistent moulins in our study area that drain the equivalent of multiple lakes per year and likely remain active over several years. Our observations indicate that once established, these persistent moulins might be capable of establishing well-connected meltwater drainage pathways.

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

“…It seems likely however that these features are largely vertical through inference from a number of lines of evidence including (i) field-based ice-penetrating radar studies [50], (ii) surface uplift in close proximity to the lake that occurs immediately following rapid lake drainage events [9,41,55] and (iii) the expectation that the physics of hydrofracture will most efficiently drive crevasses vertically from the ice surface to the bed [48]. Furthermore, it seems likely that moulins will be hydraulically efficient once formed, with turbulent and high velocity flow, in order to generate the high frictional melt rates required to prevent the closure of the englacial channels (or 'pipes') at depth where ice is often > 500 m thick.…”

“…While some meltwater is stored in supraglacial lakes, once the winter snowpack has been removed, the majority of surface meltwater is transported across the ice sheet surface in efficient supraglacial stream networks prior to delivery to crevasses and moulins [5,44,49] (near vertical pipes [50] that drain water through the ice). An extensive study across a 6812 km 2 area of the SW Greenland ice sheet betweeñ 1000-1500 m elevation [49], encompassing 523 channels that terminated in moulins, obtained mean moulin discharge of 3.15 m 3 s −1 (with a maximum of 17.7 m 3 s −1 ).…”

The annual glaciohydrology cycle in the ablation zone of the Greenland ice sheet: Part 1. Hydrology model

“…underlain by cold ice). In this $4 km portion of the flowline, we assume that ice temperature is sufficiently heterogeneous to allow the persistence of englacial conduits (Catania and Neumann, 2010). We treat the discharge of these conduits in an identical manner to the conduits downstream of the equilibrium line, except we suspend the processes that govern the transient rate of change of conduit storage volume, @S c /@t, and prescribe conduit radii as constant (5 cm).…”

A map of large Canadian eskers from Landsat satellite imagery

“…Mernild, Mote, & Liston, 2011;Rignot, Velicogna, van den Broeke, Monaghan, & Lenaerts, 2011), a large amount of research has recently been directed at furthering our understanding of how the routing and arrangement of meltwater interacts with ice flow (e.g. Catania & Neumann, 2010;Parizek, Alley, Dupont, Walker, & Anandakrishnan, 2010;Schoof, 2010;Sundal et al, 2011). However, our current understanding of meltwater drainage systems beneath the Antarctic and Greenland ice sheets is limited by the difficulty in accessing their # 2013 The Author(s).…”