Persistent flow acceleration within the interior of the Greenland ice sheet

Doyle, Samuel; Hubbard, Alun; Fitzpatrick, A.; As, Dirk van; Mikkelsen, A. B.; Pettersson, Rickard; Hubbard, Bryn

doi:10.1002/2013gl058933

Cited by 88 publications

(140 citation statements)

References 53 publications

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“…Doyle et al [92] observed a small (2.2%) increase in ice motion, from 51.78 to 52.92 m year −1 between a cooler (2009) and warmer (2012) year at a site 1840 m above sea level and 140 km from the ice sheet margin. This suggests that in regions where the ice is extremely thick (> 1500 m), and basal water flux sufficiently low, efficient subglacial drainage may not become established, allowing melt and ice motion to scale positively.…”

Section: The Greenland Ice Sheet's Dynamic Response To Meltwater Inputsmentioning

confidence: 99%

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: The Greenland Ice Sheet's Dynamic Response To Meltwater Inputsmentioning

confidence: 99%

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

View full text Add to dashboard Cite

show abstract

“…Extending the results of our model, we estimate that 48-53% more of the ice sheet will be similarly a ected. Ice in these inland areas has been shown to exhibit a positive dynamical response to increased runo 11 , in contrast to that at lower elevations, where the e ects of enhanced basal ice lubrication are o set by e cient subglacial drainage 6 .…”

mentioning

confidence: 99%

Supraglacial lakes on the Greenland ice sheet advance inland under warming climate

et al. 2014

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Supraglacial lakes (SGLs) form annually on the Greenland ice sheet 1,2 and, when they drain, their discharge enhances ice-sheet flow 3 by lubricating the base 4 and potentially by warming the ice 5 . Today, SGLs tend to form within the ablation zone, where enhanced lubrication is o set by e cient subglacial drainage 6,7 . However, it is not clear what impact a warming climate will have on this arrangement. Here, we use an SGL initiation and growth 8 model to show that lakes form at higher altitudes as temperatures rise, consistent with satellite observations 9 . Our simulations show that in southwest Greenland, SGLs spread 103 and 110 km further inland by the year 2060 under moderate (RCP 4.5) and extreme (RCP 8.5) climate change scenarios, respectively, leading to an estimated 48-53% increase in the area over which they are distributed across the ice sheet as a whole. Up to half of these new lakes may be large enough to drain, potentially delivering water and heat to the ice-sheet base in regions where subglacial drainage is ine cient. In such places, ice flow responds positively to increases in surface water delivered to the bed through enhanced basal lubrication 4,10,11 and warming of the ice 5 , and so the inland advance of SGLs should be considered in projections of ice-sheet change.The volume of water stored in SGLs on the surface of the Greenland ice sheet is determined by the presence of depressions in the local terrain 2 , by the amount of runo 8 (melt water plus rain minus refreezing in the snowpack) and by lake drainage 3 . It is estimated that 13% of Greenland's SGLs drain on timescales of the order of a few hours 12 , often by the creation of moulins as waterfilled fractures propagate through the full thickness of the ice sheet (termed hydro-fracture) 13 . SGLs act as a source of en-and subglacial water when they drain and afterwards, the moulin acts as a conduit allowing runo to pass between the ice-sheet surface and base 1,3 . Satellite and ground-based observations show a correlation between the degree of runo and the rate of ice motion 4,6,7 ; however, there are known spatial and temporal variations in the magnitude and sign of this relationship. For example, near the ice-sheet margin, lower annual ice speeds have been recorded in years of high melting 6,7 but further inland-at higher elevations-the reverse seems to be the case 4,11 . This dichotomy can be attributed to an abundance of melt water at the margin, enabling the evolution of e cient subglacial drainage early in the melt season 6,10 , and thicker ice and less water farther inland hindering the development of an e cient evacuation system 14,15 . In addition to their impact on basal sliding, draining SGLs, and moulins that persist post-drainage, can exert a local warming as relatively warm water passes through the colder

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“…Interpretation of field observations is complex, with some studies suggesting that more melt will increase annual flow [12][13][14] while others suggest the opposite [15][16][17][18] . Current theoretical understanding of GrIS basal hydrology calls on the evolution of the subglacial drainage system from low to high hydraulic efficiency, to accommodate for melt supply variability over the ablation season [19][20][21] , although limited direct observations of the basal environment do not fully verify this model [22][23][24] .…”

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confidence: 99%

Sensitive response of the Greenland Ice Sheet to surface melt drainage over a soft bed

et al. 2014

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The dynamic response of the Greenland Ice Sheet (GrIS) depends on feedbacks between surface meltwater delivery to the subglacial environment and ice flow. Recent work has highlighted an important role of hydrological processes in regulating the ice flow, but models have so far overlooked the mechanical effect of soft basal sediment. Here we use a threedimensional model to investigate hydrological controls on a GrIS soft-bedded region. Our results demonstrate that weakening and strengthening of subglacial sediment, associated with the seasonal delivery of surface meltwater to the bed, modulates ice flow consistent with observations. We propose that sedimentary control on ice flow is a viable alternative to existing models of evolving hydrological systems, and find a strong link between the annual flow stability, and the frequency of high meltwater discharge events. Consequently, the observed GrIS resilience to enhanced melt could be compromised if runoff variability increases further with future climate warming.

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Persistent flow acceleration within the interior of the Greenland ice sheet

Cited by 88 publications

References 53 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

Supraglacial lakes on the Greenland ice sheet advance inland under warming climate

Sensitive response of the Greenland Ice Sheet to surface melt drainage over a soft bed

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