9 results on '"King, Edward C."'
Search Results
2. Full-depth englacial vertical ice-sheet velocities measured using phase-sensitive radar
- Author
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Kingslake, Jonathan, Hindmarsh, Richard C. A., Aoalgeirsdottir, Guofinna, Conway, Howard, Corr, Hugh F. J., Gillet-Chaulet, Fabien, Martin, Carlos, King, Edward C., Mulvaney, Robert, and Pritchard, Hamish D.
- Subjects
Geophysics ,Glaciology--Methodology ,Ice sheets ,Hydrology ,Ice--Dynamics - Abstract
We describe a geophysical technique to measure englacial vertical velocities through to the beds of ice sheets without the need for borehole drilling. Using a ground-based phase-sensitive radio-echo sounder (pRES) during seven Antarctic field seasons, we measure the temporal changes in the position of englacial reflectors within ice divides up to 900 m thick on Berkner Island, Roosevelt Island, Fletcher Promontory and Adelaide Island. Recorded changes in reflector positions yield 'full-depth' profiles of vertical ice velocity that we use to examine spatial variations in ice flow near the divides. We interpret these variations by comparing them to the results of a full-Stokes simulation of ice-divide flow, qualitatively validating the model and demonstrating that we are directly detecting an ice-dynamical phenomenon called the Raymond Effect. Using pRES, englacial vertical ice velocities can be measured in higher spatial resolution than is possible using instruments installed within the ice. We discuss how these measurements could be used with inverse methods to measure ice rheology, and to improve ice-core dating by incorporating pRES-measured vertical velocities into age modelling.
- Published
- 2014
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3. Recent rift formation and impact on the structural integrity of the Brunt Ice Shelf, East Antarctica.
- Author
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De Rydt, Jan, Gudmundsson, G. Hilmar, Nagler, Thomas, Wuite, Jan, and King, Edward C.
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RIFTS (Geology) ,REMOTE sensing equipment ,ALGORITHMS ,ICE sheets - Abstract
We report on the recent reactivation of a large rift in the Brunt Ice Shelf, East Antarctica, in December 2012 and the formation of a 50 km long new rift in October 2016. Observations from a suite of ground-based and remote sensing instruments between January 2000 and July 2017 were used to track progress of both rifts in unprecedented detail. Results reveal a steady accelerating trend in their width, in combination with alternating episodes of fast (> 600mday
-1 ) and slow propagation of the rift tip, controlled by the heterogeneous structure of the ice shelf. A numerical ice flow model and a simple propagation algorithm based on the stress distribution in the ice shelf were successfully used to hindcast the observed trajectories and to simulate future rift progression under different assumptions. Results show a high likelihood of ice loss at the McDonald Ice Rumples, the only pinning point of the ice shelf. The nascent iceberg calving and associated reduction in pinning of the Brunt Ice Shelf may provide a uniquely monitored natural experiment of ice shelf variability and provoke a deeper understanding of similar processes elsewhere in Antarctica. [ABSTRACT FROM AUTHOR]- Published
- 2018
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4. Size, shape and spatial arrangement of mega-scale glacial lineations from a large and diverse dataset.
- Author
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Spagnolo, Matteo, Clark, Chris D., Ely, Jeremy C., Stokes, Chris R., Anderson, John B., Andreassen, Karin, Graham, Alastair G. C., and King, Edward C.
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ICE streams ,LANDFORMS ,MORPHOMETRICS ,AZIMUTH ,ICE sheets - Abstract
ABSTRACT Mega-scale glacial lineations (MSGLs) are a characteristic landform on ice stream beds. Solving the puzzle of their formation is key to understanding how ice interacts with its bed and how this, in turn, influences the dynamics of ice streams. However, a comprehensive and detailed characterization of this landform's size, shape and spatial arrangement, which might serve to test and refine formational theories, is largely lacking. This paper presents a detailed morphometric analysis and comparison of 4043 MSGLs from eight palaeo-ice stream settings: three offshore (Norway and Antarctica), four onshore (Canada), and one from under a modern ice stream in West Antarctica. The length of MSGLs is lower than previously suggested (mode 1000-2000 m; median 2892 m), and they initiate and terminate at various locations on an ice stream bed. Their spatial arrangement reveals a pattern that is characterized by an exceptional parallel conformity (80% of all mapped MSGLs have an azimuth within 5° from the mean values), and a fairly constant lateral spacing (mode 200-300 m; median 330 m), which we interpret as an indication that MSGLs are a spatially self-organized phenomenon. Results show that size, shape and spatial arrangement of MSGLs are consistent both within and also generally between different ice stream beds. We suggest this results from a common mechanism of formation, which is largely insensitive to local factors. Although the elongation of MSGLs (mode 6-8; median 12.2) is typically higher than features described as drumlins, these values and those of their width (mode 100-200 m; median 268 m) overlap, which suggests the two landforms are part of a morphological continuum and may share a similar origin. We compare their morphometry with explicit predictions made by the groove-ploughing and rilling instability theories of MSGL formation. Although the latter was most compatible, neither is fully supported by observations. © 2014 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
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5. Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts.
- Author
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Bingham, Robert G., Ferraccioli, Fausto, King, Edward C., Larter, Robert D., Pritchard, Hamish D., Smith, Andrew M., and Vaughan, David G.
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GLACIAL erosion ,ICE sheets ,RIFTS (Geology) ,SUBGLACIAL lakes ,RADAR - Abstract
Current ice loss from the West Antarctic Ice Sheet (WAIS) accounts for about ten per cent of observed global sea-level rise. Losses are dominated by dynamic thinning, in which forcings by oceanic or atmospheric perturbations to the ice margin lead to an accelerated thinning of ice along the coastline. Although central to improving projections of future ice-sheet contributions to global sea-level rise, the incorporation of dynamic thinning into models has been restricted by lack of knowledge of basal topography and subglacial geology so that the rate and ultimate extent of potential WAIS retreat remains difficult to quantify. Here we report the discovery of a subglacial basin under Ferrigno Ice Stream up to 1.5?kilometres deep that connects the ice-sheet interior to the Bellingshausen Sea margin, and whose existence profoundly affects ice loss. We use a suite of ice-penetrating radar, magnetic and gravity measurements to propose a rift origin for the basin in association with the wider development of the West Antarctic rift system. The Ferrigno rift, overdeepened by glacial erosion, is a conduit which fed a major palaeo-ice stream on the adjacent continental shelf during glacial maxima. The palaeo-ice stream, in turn, eroded the 'Belgica' trough, which today routes warm open-ocean water back to the ice front to reinforce dynamic thinning. We show that dynamic thinning from both the Bellingshausen and Amundsen Sea region is being steered back to the ice-sheet interior along rift basins. We conclude that rift basins that cut across the WAIS margin can rapidly transmit coastally perturbed change inland, thereby promoting ice-sheet instability. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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6. Kinematic waves in polar firn stratigraphy.
- Author
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Ng, Felix and King, Edward C.
- Subjects
ICE sheets ,BIOSTRATIGRAPHY ,DYNAMICS ,SLOPES (Physical geography) ,CONFIGURATIONS (Geometry) ,ARCHITECTURE ,CASE studies ,MATHEMATICAL models - Abstract
The article presents a mathematical theory to view the complex fold structures on the internal layer undulations on the ice sheets as kinetic waves in polar firn stratigraphy using visual interpretation of radargrams. In the structural architecture of layer undulations, the researchers identified the regions of positive and negative isochrone slopes on a radargram, the configuration of fold-hinge loci, and the general architecture of hinge lines on a steady-flow radargram. Case studies of a synthetic radargram and a real radargram from Bindschadler Ice Sream in the 2001/02 austral summer illustrate the retrieval of the accumulation rate and ice layer ages from stationary isochrone patterns.
- Published
- 2011
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7. Glacial geomorphology: Towards a convergence of glaciology and geomorphology.
- Author
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Bingham, Robert G., King, Edward C., Smith, Andrew M., and Pritchard, Hamish D.
- Subjects
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GEOMORPHOLOGY , *GLACIERS , *GLACIOLOGY , *GLACIAL landforms , *REMOTE sensing , *ICE shelves - Abstract
This review presents a perspective on recent trends in glacial geomorphological research, which has seen an increasing engagement with investigating glaciation over larger and longer timescales facilitated by advances in remote sensing and numerical modelling. Remote sensing has enabled the visualization of deglaciated landscapes and glacial landform assemblages across continental scales, from which hypotheses of millennial-scale glacial landscape evolution and associations of landforms with palaeo-ice streams have been developed. To test these ideas rigorously, the related goal of imaging comparable subglacial landscapes and landforms beneath contemporary ice masses is being addressed through the application of radar and seismic technologies. Focusing on the West Antarctic Ice Sheet, we review progress to date in achieving this goal, and the use of radar and seismic imaging to assess: (1) subglacial bed morphology and roughness; (2) subglacial bed reflectivity; and (3) subglacial sediment properties. Numerical modelling, now the primary modus operandi of 'glaciologists' investigating the dynamics of modern ice sheets, offers significant potential for testing 'glacial geomorphological' hypotheses of continental glacial landscape evolution and smaller-scale landform development, and some recent examples of such an approach are presented. We close by identifying some future challenges in glacial geomorphology, which include: (1) embracing numerical modelling as a framework for testing hypotheses of glacial landform and landscape development; (2) identifying analogues beneath modern ice sheets for landscapes and landforms observed across deglaciated terrains; (3) repeat-surveying dynamic subglacial landforms to assess scales of formation and evolution; and (4) applying glacial geomorphological expertise more fully to extraterrestrial cryospheres. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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8. Ice-flow reorganization in West Antarctica 2.5 kyr ago dated using radar-derived englacial flow velocities
- Author
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Kingslake, Jonathan, Martín, Carlos, Arthern, Robert J., Corr, Hugh F. J., and King, Edward C.
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Geophysics ,13. Climate action ,Glaciology ,Ice sheets ,Hydrology ,Ice--Dynamics - Abstract
We date a recent ice-flow reorganization of an ice divide in the Weddell Sea Sector, West Antarctica, using a novel combination of inverse methods and ice-penetrating radars. We invert for two-dimensional ice flow within an ice divide from data collected with a phase-sensitive ice-penetrating radar while accounting for the effect of firn on radar propagation and ice flow. By comparing isochronal layers simulated using radar-derived flow velocities with internal layers observed with an impulse radar, we show that the divide's internal structure is not in a steady state but underwent a disturbance, potentially implying a regional ice-flow reorganization, 2.5 (1.8–2.9) kyr B.P. Our data are consistent with slow ice flow in this location before the reorganization and the ice divide subsequently remaining stationary. These findings increase our knowledge of the glacial history of a region that lacks dated constraints on late-Holocene ice-sheet retreat and provides a key target for models that reconstruct and predict ice-sheet behavior.
9. Evidence for the long-term sedimentary environment in an Antarctic subglacial lake.
- Author
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Smith, Andrew M., Woodward, John, Ross, Neil, Bentley, Michael J., Hodgson, Dominic A., Siegert, Martin J., and King, Edward C.
- Subjects
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SEDIMENTARY rocks , *SUBGLACIAL lakes , *MASS-wasting (Geology) , *ICE sheets - Abstract
Abstract Lakes beneath the Antarctic Ice Sheet are of fundamental scientific interest for their ability to contain unique records of ice sheet history and microbial life in their sediments. However, no records of subglacial lake sedimentation have yet been acquired from beneath the interior of the ice sheet, and understanding of sediment pathways, processes and structure in subglacial lake environments remains uncertain. Here we present an analysis of seismic data from Subglacial Lake Ellsworth, showing that the lake bed comprises very fine-grained sediments deposited in a low energy environment, with low water- and sediment-fluxes. Minimum sediment thickness is 6 m, the result of prolonged low sedimentation rates. Based on the few available analogues, we speculate this sediment age range is a minimum of 150 ka, and possibly >1 Ma. Sediment mass movements have occurred, but they are rare and have been buried by subsequent sedimentation. We present a new conceptual model of subglacial lake sedimentation, allowing a framework for evaluating processes in subglacial lake environments, and for determining future lake access locations and interpreting subglacial lake samples. Graphical abstract Highlights • Subglacial Lake Ellsworth sediments are very soft and fine-grained. • Subglacial lake sedimentary environment is low energy and long-lived. • Sedimentation rates are very low, and persisted over a long period of time. • Sediment thickness is at least 6 m and perhaps as much as 60 m. • Subglacial lake sediment covers an age range of at least 150 ka, and possibly >1 Ma. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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