Thick sediments beneath Greenland’s ablation zone and their potential role in future ice sheet dynamics

Walter, Fabian; Chaput, Julien; Lüthi, Martin P.

doi:10.1130/g35492.1

Cited by 57 publications

(83 citation statements)

References 35 publications

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“…recently described direct observational evidence that even where channelization occurs, it is unable to explain lowering ice speed during late summer. At the extensively studied drill site FOXX in western Greenland41420212223 (Fig. 2a), water pressure in moulins feeding subglacial channels showed little change during the latter part of the melt season, yet velocities were observed to decrease over this same time period (Fig.…”

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confidence: 99%

Greenland subglacial drainage evolution regulated by weakly connected regions of the bed

et al. 2016

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Penetration of surface meltwater to the bed of the Greenland Ice Sheet each summer causes an initial increase in ice speed due to elevated basal water pressure, followed by slowdown in late summer that continues into fall and winter. While this seasonal pattern is commonly explained by an evolution of the subglacial drainage system from an inefficient distributed to efficient channelized configuration, mounting evidence indicates that subglacial channels are unable to explain important aspects of hydrodynamic coupling in late summer and fall. Here we use numerical models of subglacial drainage and ice flow to show that limited, gradual leakage of water and lowering of water pressure in weakly connected regions of the bed can explain the dominant features in late and post melt season ice dynamics. These results suggest that a third weakly connected drainage component should be included in the conceptual model of subglacial hydrology.

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confidence: 99%

Greenland subglacial drainage evolution regulated by weakly connected regions of the bed

et al. 2016

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“…More recent work supports this hypothesis that water-saturated till contributes to the flow speed on the NEGIS (Christianson et al, 2014). However, this, alongside the effect of subglacial geology, remain understudied in Greenland in contrast to Antarctica (Walter et al, 2014), and deserves further research.…”

Section: Basal Topographymentioning

confidence: 81%

A Review of Recent Changes in Major Marine-Terminating Outlet Glaciers in Northern Greenland

2017

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Over the past two decades, mass loss from the Greenland Ice Sheet (GrIS) has accelerated and contributed to global sea level rise. This has been partly attributed to dynamic changes in marine terminating outlet glaciers. Outlet glaciers at the northern margin of the ice sheet drain 40% of its area but are comparatively less well-studied than elsewhere on the ice sheet (e.g., central-west or south-east). In order to improve our understanding of this region of the GrIS, this paper synthesizes previously-published research on 21 major marine terminating outlet glaciers. Over the last 130 years, there has been a clear pattern of glacier retreat, particularly over the last two decades. This was accompanied by velocity increases on the majority of glaciers for which records exist. Despite a distinct signal of retreat, however, there is clear variability within the region, which has complicated efforts to determine the precise drivers of recent changes, such as changes in ice tongue buttressing, atmospheric and/or oceanic warming, in addition to the possibility of glacier surging. Thus, there is an important need for further work to ascertain the precise drivers of glacier change, which is likely to require datasets on recent changes in the ocean-climate system (particularly sub-surface ocean temperatures) and numerical modeling of glacier sensitivity to these various forcings. Objective identification of surge-type glaciers is also required. Given that Northern Greenland is predicted to undergo greater warming due to Arctic Amplification during the twenty-first century, we conclude that the region has the potential to become an increasingly important source of mass loss.

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“…Recent evidence [73][74][75] suggests that parts of the ice sheet are underlain by subglacial sediments. In such areas, efficient drainage where it exists is likely to be characterised by channels (or 'canals' [2]) incised both down in to the sediments as well as up into the ice, while inefficient drainage may occur via Darcian flow through the sediments [2].…”

Section: Subglacial Meltwater Processesmentioning

confidence: 99%

“…Recent surveys have reported the presence of subglacial till layers [73,74]. The significance of such layers will depend on how extensive, thick and deformable they are and, if they are pervasive, how they will impact ice dynamics in a warming world driven by the enhanced subglacial runoff.…”

Section: Subglacial Sediments and Till Deformationmentioning

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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Thick sediments beneath Greenland’s ablation zone and their potential role in future ice sheet dynamics

Cited by 57 publications

References 35 publications

Greenland subglacial drainage evolution regulated by weakly connected regions of the bed

Greenland subglacial drainage evolution regulated by weakly connected regions of the bed

A Review of Recent Changes in Major Marine-Terminating Outlet Glaciers in Northern Greenland

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

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