Seeing through deep ice
Photo: Jason Roberts & ICECAP
The focus was the heart of the Aurora Basin – a region of deep ice directly inland from Law Dome, where the Totten Glacier begins. Previously, south and west of Casey, almost nothing was known beyond three Australian ground traverses in the 1970s and 1980s. Each ICECAP flight covered in a few hours what previously took entire seasons on the ground.
ICECAP began as an International Polar Year collaborative project involving the Jackson School of Geosciences at the University of Texas, Austin; the University of Edinburgh; and the Australian Antarctic Division. It aims to uncover information critical to ice sheet modeling and an understanding of the role of the East Antarctic ice sheet in global climate and sea level rise (Australian Antarctic Magazine 15: 15, 2008).
Photo: Jack Holt
The ice penetrating radar system generates the bulk of the data – imaging the bedrock through more than four kilometers of ice and building a picture of internal reflecting layers in the ice sheet at a resolution of a couple of metres (see image). Initial processing of the first season's radar shows a wide variety of landscapes beneath the ice, from smoothly rolling plains in the deep basins, to large mountain ranges cut by deep valleys, and many indications of wet subglacial conditions and new lakes beneath the ice. Combined with the magnetic field and gravity measurements this will keep geologists busy for quite some time. Mapping out the internal layers structure within the ice will also assist in understanding present and past ice flow, and in searching for good sites for deep ice core drilling.
This 60 km section of radar signals over the Aurora Basin shows the lower half of the East Antarctic ice sheet. The strong bedrock reflection is seen through about 4 km of ice, and internal layers in the ice can be seen sweeping over an 800 m change in bedrock height.
In December 2009 ICECAP will be back at Casey, following the first major survey season out of McMurdo station in November. In addition to the original survey plans, this year ICECAP is joining NASA's Operation ICE Bridge, making extra flights along the regular satellite tracks of the satellite ICESat-I, to keep up the records of surface elevation changes in East Antarctica.
ICECAP's horizons are growing in other ways too. New French participation brings major surveys of George V Land and Eastern Wilkes Land, from Dumont d'Urville, after this year's Casey-based work. Renewal of the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) in Hobart will enable a third season of operations out of Casey in 2010–11, to explore the Denman Glacier and search for sea floor channels on the continental shelf as evidence of past ice streams.
ROLAND WARNER and JASON ROBERTS
ACE CRC and AAD