Abstract
Abstract. We identify and map visible traces of subglacial meltwater drainage around the former Keewatin Ice Divide, Canada, from high-resolution Arctic Digital Elevation Model (ArcticDEM) data. We find similarities in the characteristics and spatial locations of landforms traditionally treated separately (i.e. meltwater channels, meltwater tracks and eskers) and propose that creating an integrated map of meltwater routes captures a more holistic picture of the large-scale drainage in this area. We propose the grouping of meltwater channels and meltwater tracks under the term meltwater corridor and suggest that these features in the order of 10s–100s m wide, commonly surrounding eskers and transitioning along flow between different types, represent the interaction between a central conduit (the esker) and surrounding hydraulically connected distributed drainage system (the meltwater corridor). Our proposed model is based on contemporary observations and modelling which suggest that connections between conduits and the surrounding distributed drainage system within the ablation zone occur as a result of overpressurisation of the conduit. The widespread aerial coverage of meltwater corridors (5 %–36 % of the bed) provides constraints on the extent of basal uncoupling induced by basal water pressure fluctuations. Geomorphic work resulting from repeated connection to the surrounding hydraulically connected distributed drainage system suggests that basal sediment can be widely accessed and evacuated by meltwater.
Highlights
Variations in the configuration of subglacial hydrological systems are key to understanding some of the most dynamic ice sheet behaviour at a range of spatial and temporal scales (e.g. Zwally et al, 2002; Das et al, 2008; Joughin et al, 2008; van de Wal et al, 2008; Shepherd et al, 2009; Palmer et al, 2011; Fitzpatrick et al, 2013; Doyle et al, 2014)
We found that wider meltwater features on the order of hundreds to thousands of metres flanking or joining up intervening segments of esker ridges were common
These have previously been termed and described as different features. As they form part of the same integrated network and display similarities in spacing and morphometry, we propose collectively grouping these features under the term meltwater corridor (Table 2)
Summary
Variations in the configuration of subglacial hydrological systems are key to understanding some of the most dynamic ice sheet behaviour at a range of spatial and temporal scales (e.g. Zwally et al, 2002; Das et al, 2008; Joughin et al, 2008; van de Wal et al, 2008; Shepherd et al, 2009; Palmer et al, 2011; Fitzpatrick et al, 2013; Doyle et al, 2014). Once water reaches the bed, its impact on ice flow is determined by the hydraulic efficiency of the subglacial hydrological system. Water pressure at the bed depends on water supply to, storage within and discharge through the subglacial hydrological system (Iken et al, 1983; Kamb et al, 1985; Nienow et al, 1998). The configuration of the subglacial hydrological system is key to this, with a hydraulically efficient drainage system able to accommodate and evacuate an equivalent water flux without causing spikes in basal water pressure which have been linked to transient ice accelerations (e.g. Tedstone et al, 2013). The subglacial hydrological system has been conceptualised as a binary model comprising (i) inefficient distributed drainage – taking the form of thin films of water (Weertman, 1972), linked cavities (Lliboutry, 1968; Walder, 1986; Kamb, 1987), groundwater flow (Boulton et al, 1995)
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