Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet

Bamber, Jonathan; Siegert, Martín J.; Griggs, J. A.; Marshall, Shawn J.; Spada, Giorgio

doi:10.1126/science.1239794

Cited by 76 publications

(86 citation statements)

References 25 publications

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“…For example, studies have found that in Northern Greenland changes in the subglacial waterways are likely to have taken place during the last glacial maximum (cf. Bamber et al, 2013b). The method outlined in this paper could be used to investigate the change in subglacial drainage patterns as the ice sheet retreated and thinned after the last glacial maximum to its present-day state.…”

Section: Discussionmentioning

confidence: 99%

Response of the large-scale subglacial drainage system of Northeast Greenland to surface elevation changes

Karlsson

Dahl-Jensen

2015

The Cryosphere

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Abstract. The influence of subglacial water on the dynamics of ice flow has been the object of increasing interest in the past decade. In this study we focus on large-scale, longterm changes in surface elevation over Northeast Greenland and the corresponding changes in subglacial water routeways. Our results show that over timescales ranging from decades to millennia the area may experience redistribution of and fluctuation in subglacial water outflux under the main glacier outlets. The fluctuations in subglacial water routing occur even in the absence of external forcing. Based on these results we conclude that changes in the subglacial water routeways are an intrinsic part of the drainage basin dynamics, where the subglacial system is likely always in a transient state. The results also imply that fluctuations at the margins observed at present might originate from changes several hundred kilometres upstream. Since surface elevation changes may propagate upstream over timescales much longer than the observational period, the cause of the fluctuations may not be present in current observational records.

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Section: Discussionmentioning

confidence: 99%

Response of the large-scale subglacial drainage system of Northeast Greenland to surface elevation changes

Karlsson

Dahl-Jensen

2015

The Cryosphere

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“…Henriksen, 2008) and larger-scale landscape features including subglacial drainage networks (Cooper et al, 2016;Chu et al, 2016;Livingstone et al, 2017) and palaeofluvial canyons (such the "mega canyon" feature observed in Fig. 6e, which has Petermann glacier as its modern-day terminus) (Bamber et al, 2013b).…”

Section: Discussionmentioning

confidence: 99%

Self-affine subglacial roughness: consequences for radar scattering and basal water discrimination in northern Greenland

et al. 2017

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Abstract. Subglacial roughness can be determined at a variety of length scales from radio-echo sounding (RES) data either via statistical analysis of topography or inferred from basal radar scattering. Past studies have demonstrated that subglacial terrain exhibits self-affine (power law) roughness scaling behaviour, but existing radar scattering models do not take this into account. Here, using RES data from northern Greenland, we introduce a self-affine statistical framework that enables a consistent integration of topographicscale roughness with the electromagnetic theory of radar scattering. We demonstrate that the degree of radar scattering, quantified using the waveform abruptness (pulse peakiness), is topographically controlled by the Hurst (roughness power law) exponent. Notably, specular bed reflections are associated with a lower Hurst exponent, with diffuse scattering associated with a higher Hurst exponent. Abrupt waveforms (specular reflections) have previously been used as a RES diagnostic for basal water, and to test this assumption we compare our radar scattering map with a recent prediction for the basal thermal state. We demonstrate that the majority of thawed regions (above pressure melting point) exhibit a diffuse scattering signature, which is in contradiction to the prior approach. Self-affine statistics provide a generalised model for subglacial terrain and can improve our understanding of the relationship between basal properties and ice-sheet dynamics.

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“…We used high-resolution surface and subglacial topography, which exert primary control on the subglacial distribution and flow of water 5,63 . The geometry is prescribed using a 2008 SPOT surface digital elevation model (DEM) at 40-m resolution 64 , and a 500-m bed DEM produced from ice surface and thickness measurements from NASA's Operation IceBridge supplemented by additional radio-echo sounding data acquired by ground-based field campaigns.…”

Section: Methodsmentioning

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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Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet

Cited by 76 publications

References 25 publications

Response of the large-scale subglacial drainage system of Northeast Greenland to surface elevation changes

Response of the large-scale subglacial drainage system of Northeast Greenland to surface elevation changes

Self-affine subglacial roughness: consequences for radar scattering and basal water discrimination in northern Greenland

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

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