Seasonal changes in ice sheet motion due to melt water lubrication

Hewitt, Ian

doi:10.1016/j.epsl.2013.04.022

Cited by 193 publications

(429 citation statements)

References 55 publications

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“…These models, driven by seasonally varying supraglacial meltwater inputs, demonstrate a seasonal evolution in subglacial hydrology from distributed to channelised drainage [70][71][72] which build on the earlier theoretical work of Kamb [61]. There are however disparities between model results [65,70] and evidence from field data [55,62] in terms of the rates at which (or even whether) channels can form and the distance to which they will extend inland from the ice sheet margin.…”

Section: Subglacial Meltwater Processesmentioning

confidence: 56%

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

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

100

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Purpose of the Review This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet's hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet. Recent Findings There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland's future mass balance remains challenging.

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Section: Subglacial Meltwater Processesmentioning

confidence: 56%

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

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

100

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“…Consequently there has been renewed interest and significant progress in developing spatially distributed, coupled models of subglacial hydrology and ice flow at the glacier and ice sheet scale (e.g. Hewitt, 2013;de Fleurian et al, 2014).…”

Section: C Clason Et Al: Modelling the Transfer Of Supraglacial mentioning

confidence: 99%

Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

et al. 2015

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Abstract. Meltwater delivered to the bed of the GreenlandIce Sheet is a driver of variable ice-motion through changes in effective pressure and enhanced basal lubrication. Ice surface velocities have been shown to respond rapidly both to meltwater production at the surface and to drainage of supraglacial lakes, suggesting efficient transfer of meltwater from the supraglacial to subglacial hydrological systems. Although considerable effort is currently being directed towards improved modelling of the controlling surface and basal processes, modelling the temporal and spatial evolution of the transfer of melt to the bed has received less attention. Here we present the results of spatially distributed modelling for prediction of moulins and lake drainages on the Leverett Glacier in Southwest Greenland. The model is run for the 2009 and 2010 ablation seasons, and for future increased melt scenarios. The temporal pattern of modelled lake drainages are qualitatively comparable with those documented from analyses of repeat satellite imagery. The modelled timings and locations of delivery of meltwater to the bed also match well with observed temporal and spatial patterns of ice surface speed-ups. This is particularly true for the lower catchment ( < 1000 m a.s.l.) where both the model and observations indicate that the development of moulins is the main mechanism for the transfer of surface meltwater to the bed. At higher elevations (e.g. 1250-1500 m a.s.l.) the development and drainage of supraglacial lakes becomes increasingly important. At these higher elevations, the delay between modelled melt generation and subsequent delivery of melt to the bed matches the observed delay between the peak air temperatures and subsequent velocity speed-ups, while the instantaneous transfer of melt to the bed in a control simulation does not. Although both moulins and lake drainages are predicted to increase in number for future warmer climate scenarios, the lake drainages play an increasingly important role in both expanding the area over which melt accesses the bed and in enabling a greater proportion of surface melt to reach the bed.

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“…In Greenland, summer melt has been associated with a net speed-up as well as a net slow-down (Bartholomew et al, 2010;Palmer et al, 2011). The seasonal evolution of the drainage system is often inferred to play a dominant role: a less efficient drainage system in the early melt season can impede water flow and lead to high basal water pressures and faster sliding velocities, while a more highly developed, channelized system may lead to low water pressures and consequently to suppressed sliding velocities (see also Schoof, 2010;Hewitt, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The presence of strong diurnal cycles in water input is a key characteristic of many subglacial drainage systems during summer, leading to corresponding diurnal cycles in basal water pressure (Hubbard et al, 1995;Fudge et al, 2008;Shepherd et al, 2009) and possibly playing a role in ice flow speed-up (Schoof, 2010;Hewitt, 2013). The termination of this strong diurnal signal often occurs while there is still measurable surface melting (e.g.…”

Section: Introductionmentioning

confidence: 99%

Oscillatory subglacial drainage in the absence of surface melt

et al. 2014

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Abstract. The presence of strong diurnal cycling in basal water pressure records obtained during the melt season is well established for many glaciers. The behaviour of the drainage system outside the melt season is less well understood. Here we present borehole observations from a surge-type valley glacier in the St Elias Mountains, Yukon Territory, Canada. Our data indicate the onset of strongly correlated multi-day oscillations in water pressure in multiple boreholes straddling a main drainage axis, starting several weeks after the disappearance of a dominant diurnal mode in August 2011 and persisting until at least January 2012, when multiple data loggers suffered power failure. Jökulhlaups provide a template for understanding spontaneous water pressure oscillations not driven by external supply variability. Using a subglacial drainage model, we show that water pressure oscillations can also be driven on a much smaller scale by the interaction between conduit growth and distributed water storage in smaller water pockets, basal crevasses and moulins, and that oscillations can be triggered when water supply drops below a critical value. We suggest this in combination with a steady background supply of water from ground water or englacial drainage as a possible explanation for the observed wintertime pressure oscillations.

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Seasonal changes in ice sheet motion due to melt water lubrication

Cited by 193 publications

References 55 publications

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

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

Modelling the transfer of supraglacial meltwater to the bed of Leverett Glacier, Southwest Greenland

Oscillatory subglacial drainage in the absence of surface melt

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