scholarly journals Subglacial hydrological control on flow of an Antarctic Peninsula palaeo-ice stream

2019 ◽  
Vol 13 (6) ◽  
pp. 1583-1596 ◽  
Author(s):  
Robert D. Larter ◽  
Kelly A. Hogan ◽  
Claus-Dieter Hillenbrand ◽  
James A. Smith ◽  
Christine L. Batchelor ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Dynamic Behaviour ◽  
Stream Channels ◽  
Ice Streams ◽  
Deep Basin ◽  
Diverse Range ◽  
Ice Stream ◽  
Fast Flow ◽  
The Antarctic

Abstract. Basal hydrological systems play an important role in controlling the dynamic behaviour of ice streams. Data showing their morphology and relationship to geological substrates beneath modern ice streams are, however, sparse and difficult to collect. We present new multibeam bathymetry data that make the Anvers-Hugo Trough west of the Antarctic Peninsula the most completely surveyed palaeo-ice stream pathway in Antarctica. The data reveal a diverse range of landforms, including streamlined features where there was fast flow in the palaeo-ice stream, channels eroded by flow of subglacial water, and compelling evidence of palaeo-ice stream shear margin locations. We interpret landforms as indicating that subglacial water availability played an important role in facilitating ice stream flow and controlling shear margin positions. Water was likely supplied to the ice stream bed episodically as a result of outbursts from a subglacial lake located in the Palmer Deep basin on the inner continental shelf. These interpretations have implications for controls on the onset of fast ice flow, the dynamic behaviour of palaeo-ice streams on the Antarctic continental shelf, and potentially also for behaviour of modern ice streams.

scholarly journals Subglacial hydrological control on flow of an Antarctic Peninsula palaeo-ice stream

2019 ◽  
Author(s):  
Robert D. Larter ◽  
Kelly A. Hogan ◽  
Claus-Dieter Hillenbrand ◽  
James A. Smith ◽  
Christine L. Batchelor ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Dynamic Behaviour ◽  
Ice Streams ◽  
Deep Basin ◽  
Subglacial Lake ◽  
Ice Stream ◽  
Antarctic Continental Shelf ◽  
Geological Substrates ◽  
The Antarctic

Abstract. Basal hydrological systems play an important role in controlling the dynamic behaviour of ice streams. Data showing their morphology and relationship to geological substrates beneath modern ice streams are, however, sparse and difficult to collect. We present new multibeam bathymetry data that make the Anvers-Hugo Trough (AHT) west of the Antarctic Peninsula the most completely surveyed palaeo-ice stream pathways in Antarctica. We interpret landforms as indicating that subglacial water availability played an important role in facilitating ice stream flow and controlling shear margin positions. Water was likely supplied to the ice stream bed episodically as a result of outbursts from a subglacial lake located in the Palmer Deep basin on the inner continental shelf. These interpretations have implications for controls on the onset of fast ice flow, the dynamic behaviour of palaeo-ice streams on the Antarctic continental shelf, and potentially also for behaviour of modern ice streams.

scholarly journals Of isbræ and ice streams

2003 ◽  
Vol 36 ◽  
pp. 66-72 ◽  
Author(s):  
Martin Truffer ◽  
Keith A. Echelmeyer
Keyword(s):  
Ice Sheet ◽  
Shear Zones ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Bed Topography ◽  
Ice Stream ◽  
Fast Ice ◽  
Fast Flow ◽  
End Members

AbstractFast-flowing ice streams and outlet glaciers provide the major avenues for ice flow from past and present ice sheets. These ice streams move faster than the surrounding ice sheet by a factor of 100 or more. Several mechanisms for fast ice-stream flow have been identified, leading to a spectrum of different ice-stream types. In this paper we discuss the two end members of this spectrum, which we term the “ice-stream” type (represented by the Siple Coast ice streams in West Antarctica) and the “isbræ” type (represented by Jakobshavn Isbræ in Greenland). The typical ice stream is wide, relatively shallow (∼1000 m), has a low surface slope and driving stress (∼10 kPa), and ice-stream location is not strongly controlled by bed topography. Fast flow is possible because the ice stream has a slippery bed, possibly underlain by weak, actively deforming sediments. The marginal shear zones are narrow and support most of the driving stress, and the ice deforms almost exclusively by transverse shear. The margins seem to be inherently unstable; they migrate, and there are plausible mechanisms for such ice streams to shut down. The isbræ type of ice stream is characterized by very high driving stresses, often exceeding 200 kPa. They flow through deep bedrock channels that are significantly deeper than the surrounding ice, and have steep surface slopes. Ice deformation includes vertical as well as lateral shear, and basal motion need not contribute significantly to the overall motion. The marginal shear zone stend to be wide relative to the isbræ width, and the location of isbræ and its margins is strongly controlled by bedrock topography. They are stable features, and can only shut down if the high ice flux cannot be supplied from the adjacent ice sheet. Isbræs occur in Greenland and East Antarctica, and possibly parts of Pine Island and Thwaites Glaciers, West Antarctica. In this paper, we compare and contrast the two types of ice streams, addressing questions such as ice deformation, basal motion, subglacial hydrology, seasonality of ice flow, and stability of the ice streams.

Movements of southern elephant seals

1996 ◽  
Vol 74 (8) ◽  
pp. 1485-1496 ◽  
Author(s):  
B. J. McConnell ◽  
M. A. Fedak
Keyword(s):  
Southern Ocean ◽  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Average Rate ◽  
Stationary Phases ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
South Georgia ◽  
Southern Elephant Seals ◽  
The Antarctic

Twelve southern elephant seals (Mirounga leonina) were tracked for an average of 119 days as they left their breeding or moulting beaches on the island of South Georgia between 1990 and 1994. Females travelled either eastward up to 3000 km away to the open Southern Ocean or to the continental shelf on or near the Antarctic Peninsula. Males either stayed close to South Georgia or used South Georgia as a base for shorter trips. The females all left South Georgia in a directed manner at an average rate of 79.4 km/day over at least the first 15 days. Thereafter travel was interrupted by bouts of slower travel or stationary phases. The latter were localized at sites on the continental shelf or along its edge. Three seals that were tracked over more than one season repeated their outward direction of travel and used some of the same sites in subsequent years. The magnitude of the movements makes most of the Southern Ocean potentially available to elephant seals.

scholarly journals Ice stream or not? Radio-echo sounding of Carlson Inlet, West Antarctica

2011 ◽  
Vol 5 (4) ◽  
pp. 907-916 ◽  
Author(s):  
E. C. King
Keyword(s):  
West Antarctica ◽  
Ice Streams ◽  
Basal Resistance ◽  
Bed Topography ◽  
Ice Stream ◽  
Time Period ◽  
Adjacent Part ◽  
Radio Echo Sounding ◽  
History Of ◽  
Fast Flow

Abstract. The Antarctic Ice Sheet loses mass to the surrounding ocean mainly by drainage through a network of ice streams: fast-flowing glaciers bounded on either side by ice flowing one or two orders of magnitude more slowly. Ice streams flow despite low driving stress because of low basal resistance but are known to cease flowing if the basal conditions change, which can take place when subglacial sediment becomes dewatered by freezing or by a change in hydraulic pathways. Carlson Inlet, Antarctica has been interpreted as a stagnated ice stream, based on surface and basal morphology and shallow radar reflection profiling. To resolve the question of whether the flow history of Carlson Inlet has changed in the past, I conducted a ground-based radar survey of Carlson Inlet, the adjacent part of Rutford Ice Stream, and Talutis Inlet, West Antarctica. This survey provides details of the internal ice stratigraphy and allows the flow history to be interpreted. Tight folding of isochrones in Rutford Ice Stream and Talutis Inlet is interpreted to be the result of lateral compression during convergent flow from a wide catchment into a narrow, fast-flowing trunk. In contrast, the central part of Carlson Inlet has gently-folded isochrones that drape over the bed topography, suggestive of local accumulation and slow flow. A 1-D thermo-mechanical model was used to estimate the age of the ice. I conclude that the ice in the centre of Carlson Inlet has been near-stagnant for between 3500 and 6800 yr and that fast flow has not occurred there during that time period.

scholarly journals The relationship between sticky spots and radar reflectivity beneath an active West Antarctic ice stream

2014 ◽  
Vol 55 (67) ◽  
pp. 29-38 ◽  
Author(s):  
David W. Ashmore ◽  
Robert G. Bingham ◽  
Richard C.A. Hindmarsh ◽  
Hugh F.J. Corr ◽  
Ian R. Joughin
Keyword(s):  
Free Water ◽  
Radar Data ◽  
Force Balance ◽  
Ice Streams ◽  
West Antarctic ◽  
Ice Stream ◽  
Surface Data ◽  
Fast Flow ◽  
The Relationship ◽  
Modelling Approach

AbstractIsolated areas of high basal drag, or ‘sticky spots’, are important and poorly understood features in the force balance and dynamics of West Antarctic ice streams. Characterizing sticky spots formed by thin or drying subglacial till using ice-penetrating radar is theoretically possible, as high radar bed-returned power (BRP) is commonly related to an abundance of free water at the ice/bed interface, provided losses from englacial attenuation can be estimated. In this study we use airborne radar data collected over Evans Ice Stream to extract BRP profiles and test the sensitivity of BRP to the adopted englacial attenuation correction. We analyse 11 ~ 2 0 km profiles in four fast-flow areas where sticky spots have been inferred to exist on the basis of model and surface data inversions. In the majority of profiles we note that the increase in basal drag is accompanied by a decrease in BRP and suggest that this is evidence both for the presence of a sticky spot in those locations and that local variations in subglacial hydrology are responsible for their existence. A comparison is made between empirical and numerical modelling approaches for deriving englacial attenuation, and our findings generally support previous studies that advocate a modelling approach.

scholarly journals Oceanic Environment of George VI Ice Shelf, Antarctic Peninsula

1988 ◽  
Vol 11 ◽  
pp. 161-164 ◽  
Author(s):  
M. H. Talbot
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Sea Water ◽  
Freezing Point ◽  
Climatic Conditions ◽  
Warm Water ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Water Characteristics ◽  
The Antarctic

A collation of available data shows that sea-water with a temperature 3°C above the in-situ freezing point lies beneath George VI Ice Shelf in the Antarctic Peninsula, and is widespread on the Amundsen-Bellingshausen continental shelf. The presence of warm water is a factor in the recent and continuing disintegration of ice shelves in the region, yet the meteorology and oceanography of the sector are little known. We discuss a plausible link between the present climatic conditions, sea-water characteristics and the warm-water intrusion on to the continental shelf, thereby illustrating an indirect climatic influence on the mass balance of ice shelves.

scholarly journals Evolution of subglacial bedforms along a paleo-ice stream, Antarctic Peninsula continental shelf

2002 ◽  
Vol 29 (8) ◽  
pp. 41-1-41-4 ◽  
Author(s):  
Colm Ó Cofaigh ◽  
Carol J. Pudsey ◽  
Julian A. Dowdeswell ◽  
Peter Morris
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Ice Stream

scholarly journals A groove-ploughing theory for the production of mega-scale glacial lineations, and implications for ice-stream mechanics

2003 ◽  
Vol 49 (165) ◽  
pp. 240-256 ◽  
Author(s):  
Chris D. Clark ◽  
Slawek M. Tulaczyk ◽  
Chris R. Stokes ◽  
Miquel Canals
Keyword(s):  
Qualitative Theory ◽  
Transverse Strain ◽  
Supporting Evidence ◽  
Ice Streams ◽  
Flow Acceleration ◽  
High Magnitude ◽  
Ice Stream ◽  
Roughness Elements ◽  
Stream Beds ◽  
Fast Flow

AbstractMega-scale glacial lineations (MSGLs) are longitudinally aligned corrugations (ridge–groove structures 6–100 km long) in sediment produced subglacially. They are indicators of fast flow and a common signature of ice-stream beds. We develop a qualitative theory that accounts for their formation, and use numerical modelling, and observations of ice-stream beds to provide supporting evidence. Ice in contact with a rough (scale of 10–103 m) bedrock surface will mimic the form of the bed. Because of flow acceleration and convergence in ice-stream onset zones, the ice-base roughness elements experience transverse strain, transforming them from irregular bumps into longitudinally aligned keels of ice protruding downwards. Where such keels slide across a soft sedimentary bed, they plough through the sediments, carving elongate grooves, and deforming material up into intervening ridges. This explains MSGLs and has important implications for ice-stream mechanics. Groove ploughing provides the means to acquire new lubricating sediment and to transport large volumes of it downstream. Keels may provide basal drag in the force budget of ice streams, thereby playing a role in flow regulation and stability. We speculate that groove ploughing permits significant ice-stream widening, thus facilitating high-magnitude ice discharge.

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