Authors / CoAuthors
O'Brien, P.E. | Post, A.L. | Hemer, M. | Craven, M.
Abstract
Antarctic ice shelves and fast flowing ice streams are key drainage features of the Antarctic Ice Sheet and their behaviour determines the sensitivity of the ice sheet to climate change and sea level rise. Some fast flowing ice streams are thinning rapidly and could be the 'soft underbelly' of the East Antarctic Ice sheet. Processes across the grounding zone are important in understanding the retreat behaviour of ice streams but are poorly understood because of the difficulty of accessing the region. The Antarctic Shelf preserves geomorphic features and sedimentary structures left by ice retreat which can provide insights into processes in and close to the grounding zone. Sidescan sonar records from Prydz Bay image a range of features that reflect changes in processes across the Amery Ice Shelf grounding zone during retreat after the Last Glacial Maximum. The major features identified are: Mega-scale Glacial Lineations Linear ridges of sediment formed by moulding of mobile subglacial sediment parallel to ice flow. Flutes and Mega flutes - Smaller linear ridges moulded by ice flow. Inter-flute dunes - Large bedforms formed by bottom currents flowing the grounding zone in the sub-ice shelf cavity. Transverse steps - Ice flow parallel ridges that terminate in steps running oblique to normal to the ice flow direction. Sinuous ridges (Eskers) - Gently sinuous ridges that run generally parallel to obliquely across fluted surfaces. Polygonal crevasse infills - Irregular polygonal ridges on the crest of grounding zone wedges. The presence of fluted and mega-scale glacial lineations indicates that the ice moved over an unfrozen, deforming bed in the zone up stream of the grounding zone. For most of the Amery Ice Shelf, the inter-flute dunes reflect strong thermohaline circulation in the ice shelf cavity. Sand and gravel recovered in cores from beneath the Amery Ice Shelf indicate significant current speeds, possibly enhanced by tidal pumping.
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nonGeographicDataset
eCat Id
70257
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- External PublicationAbstract
- ( Theme )
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- Antarctic data
- ( Theme )
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- geomorphology
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- AQ
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2010-01-01T00:00:00
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geoscientificInformation
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