The Dynamics of the Outlet Glaciers
Metadata record for data from ASAC Project 457 See the link below for public details on this project. From the abstracts of the referenced papers: ####################### A comprehensive, airborne survey of the Vanderford and Adams glaciers was started in January 1983, continued through the austral...
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| Format: | Dataset |
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Australian Antarctic Data Centre
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| Online Access: | https://researchdata.ands.org.au/dynamics-outlet-glaciers/700214 https://data.aad.gov.au/metadata/records/ASAC_457 http://nla.gov.au/nla.party-617536 |
| Summary: | Metadata record for data from ASAC Project 457 See the link below for public details on this project. From the abstracts of the referenced papers: ####################### A comprehensive, airborne survey of the Vanderford and Adams glaciers was started in January 1983, continued through the austral summer season 1984/5, and completed in February 1985. Ice thickness and surface-elevation data were collected over some 4500 square kilometres, on a grid spacing of approximately 5 kilometres. The measurement system was based on a Bell 206 helicopter, fitted with ANARE 100 MHz ice radar, Motorola Mini-Ranger navigation equipment, and a digital, pressure altimeter. A JMR, satellite, doppler receiver was used to position the navigation ground stations precisely. Gravity measurements were used to fill in ice-thickness coverage, where the ice radar failed to produce an echo and also to help determine where the glacier was floating. Ice-movement profiles were measured across the front sections of the glaciers and additional spot values were obtained further upstream by utilizing the 3 m accuracy of the navigation equipment to locate markers quickly at both the beginning and end of the seasons work. A data logger in the helicopter recorded time, navigation distances, aircraft to ground clearance, and air pressure, at 10 second intervals. These data were later merged with manually-scaled, ice-thickness values, for computer processing. The results show that the Vanderford glacier dominates the system and drains about 5 cubic kilometres of ice per annum, mainly from the inland ice sheet to the south. Ice flowing into the Adams Glacier tends to come from nearer the coast and to the south and west of the glacier. Bedrock topography beneath the Vanderford shows that the deep, inland trench, similar to that found below other outlet glaciers, drops to 2500 m below sea level, 60 kilometres from the front. The trench has steep sides to the east and gives a clearly-defined edge to the fast glacier flow. The western side, however, is much more complicated, particularly further inland, where the flow is not clearly separate from ####################### Glacier velocities have been measured using satellite imagery by scaling and comparing photographic images that have been acquired over time intervals of about 10 years. A pilot project was undertaken on Denman Glacier to develop techniques for the measurement of glacier velocities directly on the original digital image data rather than on photographic products, and to determine the potential accuracy of the results. Denman Glacier is clearly discernible in Landsat images as a well-defined ice stream from south of Mount Strathcona through to the northern boundary of Shackleton Ice Shelf, a distance of 250 km. There are surface features visible along most of its length which persist with time and move with the glacier. They can be identified in two separate Landsat images which have an intervening time interval of 1.24 years. ####################### Surveys of ice thickness, surface elevation, velocity, and accumulation rate were made on the upper part of Totten Glacier by oversnow traverse during 1987. Measurements were made along one longitudinal section and three cross-sections of the deep broad valley the glacier occupies along the south-east margin of Law Dome in Wilkes Land. The valley connects with Vanderford Glacier to the west and separates Law Dome ice cap from the main Antarctic ice sheet. The lowest measurements were located about 125 km in from where the glacier tongue emerges from the coastline. Other measurements made on the grounded ice sheet in Wilkes Land (Young and others, 1989) provide data on the flow immediately inland of Totten Glacier. The ice thickness in the glacier valley varies between 1400 m and 2800 m,but is typically about 2000 m over a large part of the survey area. The thickest ice, 2825 m, occurs where the surface elevation is only 300 m, and the base of the ice is 2525 m below sea level, which suggests that the ice stream could be floating at this point. The greatest measured velocity, 730 m a-1 , occurs within 4 km of this point. By contrast the velocity on the southern boundary is 710 m a-1 in ice only 1400 m thick. The maximum down slope shear stress of 1.8 bar occurs about 40 km up-stream of the lowest cross section where the ice is about 1500 m thick, with surface elevation about 1000 m and surface velocity of 333 m a-1. Extrapolation of the trend in velocity and longitudinal strain-rate to the glacier front suggests that the outlet velocity could be of the order of 2-3 km a-1. The mass flux through the lowest cross section is estimated to be in excess of 40 Gt a-1. Snow accumulation on the surface of the glacier of the order of 1000-2000 kg m-2 a-1 will contribute about 1 Gt a-1 to the total flux. |
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