ORCID Profile
0000-0001-7196-4171
Current Organisation
University of Cambridge
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Publisher: American Geophysical Union (AGU)
Date: 04-11-2011
DOI: 10.1029/2011JF002025
Publisher: Springer Science and Business Media LLC
Date: 14-03-2018
DOI: 10.1038/S41467-018-03420-8
Abstract: Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed. Here we use a well-constrained 3D model to demonstrate that supraglacial lakes in Greenland drain when tensile-stress perturbations propagate fractures in areas where fractures are normally absent or closed. These melt-induced perturbations escalate when lakes as far as 80 km apart form expansive networks and drain in rapid succession. The result is a tensile shock that establishes new surface-to-bed hydraulic pathways in areas where crevasses transiently open. We show evidence for open crevasses 135 km inland from the ice margin, which is much farther inland than previously considered possible. We hypothesise that inland expansion of lakes will deliver water and heat to isolated regions of the ice sheet’s interior where the impact on ice flow is potentially large.
Publisher: American Geophysical Union (AGU)
Date: 2019
DOI: 10.1029/2018JF004821
Publisher: Geological Society of America
Date: 08-2012
DOI: 10.1130/G33036.1
Publisher: American Geophysical Union (AGU)
Date: 07-02-2013
DOI: 10.1029/2012JF002570
Publisher: Wiley
Date: 05-09-2020
Publisher: American Geophysical Union (AGU)
Date: 02-2018
DOI: 10.1002/2017JF004529
Publisher: American Geophysical Union (AGU)
Date: 09-2021
DOI: 10.1029/2021JF006287
Abstract: Surface crevasses on the Greenland Ice Sheet (GrIS) capture nearly half of the seasonal runoff, yet their role in transferring meltwater to the bed has received little attention relative to that of supraglacial lakes and moulins. Here, we present observations of crevasse ponding and investigate controls on their hydrological behavior at a fast‐moving, marine‐terminating sector of the GrIS. We map surface meltwater, crevasses, and surface‐parallel stress across a ∼2,700 km 2 region using satellite data and contemporaneous uncrewed aerial vehicle (UAV) surveys. From 2017 to 2019 an average of 26% of the crevassed area exhibited ponding at locations that remained persistent between years despite rapid advection. We find that the spatial distribution of ponded crevasses does not relate to previously proposed controls on the distribution of supraglacial lakes (elevation and topography) or crevasses (von Mises stress thresholds), suggesting the operation of some other physical control(s). Ponded crevasse fields were preferentially located in regions of compressive surface‐parallel mean stress, which we interpret to result from the hydraulic isolation of these systems. This contrasts with unponded crevasse fields, which we suggest are readily able to transport meltwater into the wider supraglacial and englacial network. UAV observations show that ponded crevasses can drain episodically and rapidly, likely through hydrofracture. We therefore propose that the surface stress regime influences a spatially heterogeneous transfer of meltwater through crevasses to the bed of ice sheets, with consequences for processes, such as subglacial drainage and the heating of ice via latent heat release by refreezing meltwater.
Publisher: American Geophysical Union (AGU)
Date: 21-10-2015
DOI: 10.1002/2015GL065782
Publisher: Wiley
Date: 14-05-2020
Publisher: Wiley
Date: 30-04-2021
Publisher: Geological Society of London
Date: 25-05-2017
DOI: 10.1144/SP461.8
Publisher: American Geophysical Union (AGU)
Date: 02-2014
DOI: 10.1002/2013JF002958
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-05-2021
Abstract: High-resolution observations from a 1043-m-deep borehole show highly variable ice properties and heterogeneous deformation.
Publisher: American Geophysical Union (AGU)
Date: 2019
DOI: 10.1029/2018JF004707
Publisher: Wiley
Date: 27-12-2020
Publisher: Proceedings of the National Academy of Sciences
Date: 22-02-2022
Abstract: Subglacial drainage systems control ice sheet flow and the quantity of ice discharged into the ocean. However, these systems are currently poorly characterized, from a lack of direct observations. This shortcoming is problematic, as changes in drainage systems can result in a markedly differently ice sheet response. Here, we present a radar-derived record of basal melt rates with colocated borehole observations, showing unexpectedly warm subglacial conditions beneath a large outlet glacier in West Greenland. The record is unprecedented because the observed basal melt rates are several orders of magnitude higher than predictions and previous estimates. Our observations show that the effect of viscous dissipation from surface meltwater input is by far the largest heat source beneath the Greenland Ice Sheet.
Publisher: Springer Science and Business Media LLC
Date: 29-09-2014
DOI: 10.1038/NCOMMS6052
Abstract: 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 three-dimensional 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.
Publisher: American Geophysical Union (AGU)
Date: 06-2021
DOI: 10.1029/2020AV000291
Abstract: Optical televiewer borehole logging within a crevassed region of fast‐moving Store Glacier, Greenland, revealed the presence of 35 high‐angle planes that cut across the background primary stratification. These planes were composed of a bubble‐free layer of refrozen ice, most of which hosted thin laminae of bubble‐rich “last frozen” ice, consistent with the planes being the traces of former open crevasses. Several such last‐frozen laminae were observed in four traces, suggesting multiple episodes of crevasse reactivation. The frequency of crevasse traces generally decreased with depth, with the deepest detectable trace being 265 m below the surface. This is consistent with the extent of the warmer‐than‐modeled englacial ice layer in the area, which extends from the surface to a depth of ∼400 m. Crevasse trace orientation was strongly clustered around a dip of 63° and a strike that was offset by 71° from orthogonal to the local direction of principal extending strain. The traces’ antecedent crevasses were therefore interpreted to have originated upglacier, probably ∼8 km distant involving mixed‐mode (I and III) formation. We conclude that deep crevassing is pervasive across Store Glacier, and therefore also at all dynamically similar outlet glaciers. Once healed, their traces represent planes of weakness subject to reactivation during subsequent advection through the glacier. Given their depth, it is highly likely that such traces—particularly those formed downglacier—survive surface ablation to reach the glacier terminus, where they may represent foci for fracture and iceberg calving.
Publisher: American Geophysical Union (AGU)
Date: 26-03-2014
DOI: 10.1002/2014GL059250
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-08-2017
Abstract: Seismic data show that subglacial sediment slip causes a complex flow response of the Greenland Ice Sheet to climate warming.
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
Location: France
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2009
End Date: 2013
Funder: Natural Environment Research Council
View Funded ActivityStart Date: 2013
End Date: 2017
Funder: Natural Environment Research Council
View Funded ActivityStart Date: 2013
End Date: 2017
Funder: Natural Environment Research Council
View Funded ActivityStart Date: 2007
End Date: 2011
Funder: Natural Environment Research Council
View Funded Activity