scholarly journals Longitudinal surface structures (flowstripes) on Antarctic glaciers

2011 ◽  
Vol 5 (6) ◽  
pp. 3085-3112 ◽  
Author(s):  
N. F. Glasser ◽  
G. H. Gudmundsson
Keyword(s):  
Ross Sea ◽  
Extensional Flow ◽  
Surface Expression ◽  
Surface Structures ◽  
Schematic Model ◽  
Shelf Area ◽  
Ice Shelf ◽  
Flow Units ◽  
Glacier Flow ◽  
Optical Satellite Images

Abstract. Longitudinal surface structures (''flowstripes'') are common on many glaciers but their origin and significance are poorly understood. In this paper we present observations of the development of these longitudinal structures from four different Antarctic glacier systems (the Lambert Glacier/Amery Ice Shelf area, outlet glaciers in the Ross Sea sector, ice-shelf tributary glaciers on the Antarctic Peninsula, and the onset zone of a tributary to the Recovery Glacier Ice Stream in the Filchner Ice Shelf area). Mapping from optical satellite images demonstrates that longitudinal surface structures develop in two main situations: (1) as relatively wide flow stripes within glacier flow units and (2) as relatively narrow flow stripes where there is convergent flow around nunataks or at glacier confluence zones. Our observations indicate that the confluence features are narrower, sharper, and more clearly defined features. They are characterised by linear troughs or depressions on the ice surface and are much more common than the former type. Longitudinal surface structures within glacier flow units have previously been explained as the surface expression of localised bed perturbations but a universal explanation for those forming at glacier confluences is lacking. Here we propose that these features are formed at zones of ice acceleration and extensional flow at glacier confluences. We provide a schematic model for the development of longitudinal surface structures based on extensional flow that can explain their ridge and trough morphology as well as their down-ice persistence.

scholarly journals Longitudinal surface structures (flowstripes) on Antarctic glaciers

2012 ◽  
Vol 6 (2) ◽  
pp. 383-391 ◽  
Author(s):  
N. F. Glasser ◽  
G. H. Gudmundsson
Keyword(s):  
Ross Sea ◽  
Extensional Flow ◽  
Surface Expression ◽  
Surface Structures ◽  
Schematic Model ◽  
Shelf Area ◽  
Ice Shelf ◽  
Flow Units ◽  
Glacier Flow ◽  
Optical Satellite Images

Abstract. Longitudinal surface structures ("flowstripes") are common on many glaciers but their origin and significance are poorly understood. In this paper we present observations of the development of these longitudinal structures from four different Antarctic glacier systems; the Lambert Glacier/Amery Ice Shelf area, the Taylor and Ferrar Glaciers in the Ross Sea sector, Crane and Jorum Glaciers (ice-shelf tributary glaciers) on the Antarctic Peninsula, and the onset zone of a tributary to the Recovery Glacier Ice Stream in the Filchner Ice Shelf area. Mapping from optical satellite images demonstrates that longitudinal surface structures develop in two main situations: (1) as relatively wide flow stripes within glacier flow units and (2) as relatively narrow flow stripes where there is convergent flow around nunataks or at glacier confluence zones. Our observations indicate that the confluence features are narrower, sharper, and more clearly defined features. They are characterised by linear troughs or depressions on the ice surface and are much more common than the former type. Longitudinal surface structures within glacier flow units have previously been explained as the surface expression of localised bed perturbations but a universal explanation for those forming at glacier confluences is lacking. Here we propose that these features are formed at zones of ice acceleration and extensional flow at glacier confluences. We provide a schematic model for the development of longitudinal surface structures based on extensional flow that can explain their ridge and trough morphology as well as their down-ice persistence.

scholarly journals A structural glaciological analysis of the 2002 Larsen B ice-shelf collapse

2008 ◽  
Vol 54 (184) ◽  
pp. 3-16 ◽  
Author(s):  
N.F. Glasser ◽  
T.A. Scambos
Keyword(s):  
Surface Structures ◽  
Velocity Mapping ◽  
Ice Shelf ◽  
Lateral Shear ◽  
Source Areas ◽  
Flow Units ◽  
Zone Velocity ◽  
Break Up ◽  
Glacier Flow ◽  
The Antarctic

AbstractThis study provides a detailed structural glaciological analysis of changes in surface structures on the Larsen B ice shelf on the Antarctic Peninsula prior to its collapse in February–March 2002. Mapped features include the ice-shelf front, rifts, crevasses, longitudinal linear surface structures and meltwater features. We define domains on the ice shelf related to glacier source areas and demonstrate that, prior to collapse, the central Larsen B ice shelf consisted of four sutured flow units fed by Crane, Jorum, Punchbowl and Hektoria/Green/Evans glaciers. Between these flow units were ‘suture zones’ of thinner ice where the feeder glaciers merged. Prior to collapse, large open-rift systems were present offshore of Foyn Point and Cape Disappointment. These rifts became more pronounced in the years preceding break-up, and ice blocks in the rifts rotated because of the strong lateral shear in this zone. Velocity mapping of the suture zones indicates that the major rifts were not present more than about 20 years ago. We suggest that the ice shelf was preconditioned to collapse by partial rupturing of the sutures between flow units. This, we believe, was the result of ice-shelf front retreat during 1998–2000, reducing the lateral resistive stress on the upstream parts of the shelf and glacier flow units, ice-shelf thinning and pre-shelf-break-up glacier acceleration.

scholarly journals Ice Movement Studies on the Skelton Glacier

1961 ◽  
Vol 3 (29) ◽  
pp. 873-878
Author(s):  
Charles R. Wilson ◽  
A. P. Crary
Keyword(s):  
Ross Sea ◽  
Ice Thickness ◽  
Strain Rates ◽  
Shelf Area ◽  
Dry Valleys ◽  
Ice Shelf ◽  
The West ◽  
Ross Ice Shelf ◽  
High Plateau ◽  
Plateau Area

The volume of ice that flows annually from the Skelton Glacier on the west side of the Ross Ice Shelf between the Worcester and Royal Society Ranges was determined during 1958–59 traverse operations to be approximately 791 × 106 m.3 or 712 × 106 m.3 water equivalent. Annual accumulation on the Skelton névé field and small cirque glaciers is estimated to be 1,018 × 106 m.3 water equivalent, but this figure can be reduced to 712 × 106 m.3 by assuming that 30 per cent of the expected accumulation in the lower slopes of the glacier is lost to adjacent areas of the Ross Ice Shelf by katabatic winds. It is evident that little or no contribution to the nourishment of the Skelton Glacier comes from the high plateau area of East Antarctica. It is suggested that this condition exists generally in the western Ross Sea and Ross Shelf area, and is responsible for the existence of the present “dry” valleys in the McMurdo Sound area.Some estimates of local ice regime are made at two sites on the glacier where ice thickness and strain rates are known.

Tides of the Ross Sea and Ross Ice Shelf cavity

2003 ◽  
Vol 15 (1) ◽  
pp. 31-40 ◽  
Author(s):  
LAURENCE PADMAN ◽  
SVETLANA EROFEEVA ◽  
IAN JOUGHIN
Keyword(s):  
Ross Sea ◽  
Spring Tide ◽  
Model Performance ◽  
Tidal Currents ◽  
Tidal Range ◽  
Ocean Tide ◽  
Shelf Area ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Ocean Tide Models

Two new ocean tide models for the Ross Sea including the ocean cavity under the Ross Ice Shelf, are described. The optimum model for predicting ice shelf surface height variability is based on assimilation of gravimetry-derived tidal constituents from the Ross Ice Shelf. Synthetic aperture radar interferograms provide an independent test of model performance. The standard deviation of tide height variability is largest under the eastern ice shelf along the Shirase and Siple Coasts, where it can exceed 0.8 m. The maximum peak-to-peak tidal range in this region is ∼3 m. The best predictor for ocean tidal currents north of the ice front is a dynamics-based model that solves the depth-integrated shallow water equations with a linear representation of benthic friction rather than the more usual quadratic form. Tidal currents over the open Ross Sea are dominated by diurnal, topographically trapped vorticity waves. The strongest modelled currents exceed 1 m s−1 at spring tide in a narrow band along the upper continental slope in the north-western Ross Sea. Typical tidal currents in the central continental shelf area of the Ross Sea are 10–20 cm s−1. Under the ice shelf the typical currents are ∼5 cm s−1.

Continued northward expansion of the Ross Ice Shelf, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 93-98 ◽  
Author(s):  
Harry J. R. Keys ◽  
Stanley S. Jacobs ◽  
Lawson W. Brigham
Keyword(s):  
Ross Sea ◽  
Shelf Area ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Ross Ice Shelf ◽  
Front Advance ◽  
Northward Expansion ◽  
High Elevations ◽  
The Antarctic ◽  
Local Variability

The last major calving event along the Ross Ice Shelf (RIS, Antarctica) front occurred a decade ago, following a substantial increase in the rate of ice-front advance in the few years preceding the event. This “B-9” event, on the eastern part of the front between Edward VII Peninsula and Roosevelt Island, removed ≈ 5100 km2of ice, about 100 years of advance in that sector, but reduced the ice-shelf area by only 1%. Since 1987 the entire ice front has continued to advance, more than regaining the area lost during the B-9 event. The western front is now well north of any position recorded during the last 150 years, and it lias not experienced major calving forat least 90 years. Ice-front heights generally decrease from east to west, but local variability is high. Elevations are relatively low from 171° to 177° W, the location of “warm” Modified Circumpolar Deep Water circulation beneath the outer ice shelf. Modern heights considerably exceed historical heights between 179° Wand 178° E and are lower west of 174° E, probably due to recent dynamic changes such as rifting and the western advance. The general advance of the RIS front and the period of several decades to more than a century that elapses between major calving events is consistent with a relatively stable ice front. This contrasts with several smaller ice shelves along the Antarctic Peninsula and McMurdo Ice Shelf in the Ross Sea which have retreated substantially during the past few decades.

scholarly journals Ice Movement Studies on the Skelton Glacier

1961 ◽  
Vol 3 (29) ◽  
pp. 873-878 ◽  
Author(s):  
Charles R. Wilson ◽  
A. P. Crary
Keyword(s):  
Ross Sea ◽  
Ice Thickness ◽  
Strain Rates ◽  
Shelf Area ◽  
Dry Valleys ◽  
Ice Shelf ◽  
The West ◽  
Ross Ice Shelf ◽  
High Plateau ◽  
Plateau Area

The volume of ice that flows annually from the Skelton Glacier on the west side of the Ross Ice Shelf between the Worcester and Royal Society Ranges was determined during 1958–59 traverse operations to be approximately 791 × 106 m.3 or 712 × 106 m.3 water equivalent. Annual accumulation on the Skelton névé field and small cirque glaciers is estimated to be 1,018 × 106 m.3 water equivalent, but this figure can be reduced to 712 × 106 m.3 by assuming that 30 per cent of the expected accumulation in the lower slopes of the glacier is lost to adjacent areas of the Ross Ice Shelf by katabatic winds. It is evident that little or no contribution to the nourishment of the Skelton Glacier comes from the high plateau area of East Antarctica. It is suggested that this condition exists generally in the western Ross Sea and Ross Shelf area, and is responsible for the existence of the present “dry” valleys in the McMurdo Sound area. Some estimates of local ice regime are made at two sites on the glacier where ice thickness and strain rates are known.

scholarly journals Evidence for a Former Large Ice Sheet in the Orville Coast–Ronne Ice Shelf Area, Antarctica

1981 ◽  
Vol 27 (97) ◽  
pp. 487-491
Author(s):  
Paul Carrara
Keyword(s):  
Sea Level ◽  
Ross Sea ◽  
Ice Sheet ◽  
Shelf Area ◽  
Sea Level Changes ◽  
Ice Shelf ◽  
The Past ◽  
The World ◽  
History Of ◽  
The Antarctic

AbstractThe Orville Coast area of the Antarctic Peninsula was extensively glacierized in the past. Striations, polished rock surfaces, and erratics on nunatak summits indicate that this area was covered by a broad regional ice sheet whose grounded ice margin was on the continental shelf, in the present-day Ronne Ice Shelf area. If the glacial history of Antarctica has been controlled by eustatic sea-level changes, the destruction of this ice sheet would have been contemporaneous with that of the Ross Sea ice sheet due to the world-wide rise of eustatic sea-level at the end of the Wisconsin glaciation.

scholarly journals Evidence for a Former Large Ice Sheet in the Orville Coast–Ronne Ice Shelf Area, Antarctica

1981 ◽  
Vol 27 (97) ◽  
pp. 487-491 ◽  
Author(s):  
Paul Carrara
Keyword(s):  
Sea Level ◽  
Ross Sea ◽  
Ice Sheet ◽  
Shelf Area ◽  
Sea Level Changes ◽  
Ice Shelf ◽  
The Past ◽  
The World ◽  
History Of ◽  
The Antarctic

AbstractThe Orville Coast area of the Antarctic Peninsula was extensively glacierized in the past. Striations, polished rock surfaces, and erratics on nunatak summits indicate that this area was covered by a broad regional ice sheet whose grounded ice margin was on the continental shelf, in the present-day Ronne Ice Shelf area. If the glacial history of Antarctica has been controlled by eustatic sea-level changes, the destruction of this ice sheet would have been contemporaneous with that of the Ross Sea ice sheet due to the world-wide rise of eustatic sea-level at the end of the Wisconsin glaciation.

scholarly journals Surface structure and stability of the Larsen C ice shelf, Antarctic Peninsula

2009 ◽  
Vol 55 (191) ◽  
pp. 400-410 ◽  
Author(s):  
N.F. Glasser ◽  
B. Kulessa ◽  
A. Luckman ◽  
D. Jansen ◽  
E.C. King ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Satellite Image ◽  
Austral Summer ◽  
Shelf Area ◽  
Shelf Edge ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Flow Units ◽  
Grounding Line ◽  
Longitudinal Structures

AbstractA structural glaciological description and analysis of surface morphological features of the Larsen C ice shelf, Antarctic Peninsula, is derived from satellite images spanning the period 1963–2007. The data are evaluated in two time ranges: a comparison of a 1963 satellite image photomosaic with a modern digital mosaic compiled using 2003/04 austral summer data; and an image series since 2003 showing recent evolution of the shelf. We map the ice-shelf edge, rift swarms, crevasses and crevasse traces, and linear longitudinal structures (called ‘flow stripes’ or ‘streak lines’). The latter are observed to be continuous over distances of up to 200 km from the grounding line to the ice-shelf edge, with little evidence of changes in pattern over that distance. Integrated velocity measurements along a flowline indicate that the shelf has been stable for ∼560 years in the mid-shelf area. Linear longitudinal features may be grouped into 12 units, each related to one or a small group of outlet feeder glaciers to the shelf. We observe that the boundaries between these flow units often mark rift terminations. The boundary zones originate upstream at capes, islands or other suture areas between outlet glaciers. In agreement with previous work, our findings imply that rift terminations within such suture zones indicate that they contain anomalously soft ice. We thus suggest that suture zones within the Larsen C ice shelf, and perhaps within ice shelves more generally, may act to stabilize them by reducing regional stress intensities and thus rates of rift lengthening.

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