Aims and Science Overview The traditionally accepted model of ice-sheet discharge is that fast-flowing outlet glaciers and ice streams drain a slow moving reservoir of ice in the interior of the ice-sheet. It is also generally thought that the transition zone between fast flow features and slow inland regions is abrupt.
However, recent modelling of balance velocities (the depth-averaged velocity required to keep the ice sheet in a state of balance) has indicated that this traditional model of ice-sheet discharge is too simplistic, and that instead, complex systems of enhanced flow penetrate up to 1000 km into the ice-sheet’s interior. The processes that define and control this newly identified flow-state are largely unknown, and there is currently a lack of data available that could be used to gain an understanding of it. Widespread enhanced flow does, however, have far-reaching implications for understanding the dynamics of large ice masses, which in turn is crucial for improving estimates of present-day and possible future changes in mass balance.
No theories currently exist to explain the controls on enhanced flow. However, work to date has indicated that basal topography is an important control, and existing RES data from other parts of Antarctica have shown that in regions of enhanced flow, otherwise continuous internal layers become buckled and deformed - a common occurrence where basal sliding is important.
The primary objective of this project is therefore to investigate this newly discovered enhanced flow in order to clarify and understand the factors controlling it. This work is being carried out in the onset region of the Bailey/Slessor glacier system in East Antarctica, where enhanced flow tributaries have been shown to extend ~600km inland from the grounding line.
Methodology and Logistics
In order to achieve this objective, an airborne survey employing radio-echo sounding (RES) has been carried out to measure the ice thickness, internal ice properties and the characteristics of the ice/bedrock interface. A field-camp and fuel depot was set up at 78°58.60’ S, 007°24.97’ W, located ~600km from Halley. Five separate survey flights were designed, starting and ending at the field camp, each covering a distance of ~1000km. These flights were designed to be flown in five separate sorties, however concerns over possible delays due to potentially adverse weather, led to all flights being completed on three consecutive days of excellent conditions, between Saturday 15th and Monday 17th December 2001, inclusive.
In addition to RES data collected in support of GR3/AFI2/65, magnetometer data was also acquired during the sorties on an opportunistic basis. Snow samples were also collected and will be transported back to the UK in order to carry out chemical and oxygen isotope analysis.
Future work
The next two years will see the processing and analysis of the data collected during this field season. The resulting data-set will be used in conjunction with satellite-derived surface velocity data to investigate the factors that influence the location and extent of enhanced flow.