The surface elevation of the Antarctic Ice Sheet (AIS) should change only slowly, as patterns of snow accumulation vary from year to year, or century to century, and as the rate of flow of the ice sheet towards the sea changes through time. Recently, satellite data has shown that small parts of the ice sheet surface, often less than 10 km across, have experienced very rapid elevation change, of up to 6m, at rates of over 2 cm/day. These elevation change anomalies (ECAs) are sometimes found in clusters, with some parts of the surface sinking, while other areas down-gradient on the ice sheet, show the surface rising. Researchers have suggested that these rapid changes of ice sheet surface elevation associated with these ECAs may represent the filling or draining of water pockets (subglacial lakes) at the bottom of the AIS. These water pockets are believed to be part of a wider network of lakes, rivers and shallow swamps between the glacier ice at the bottom of the AIS and the sediments and bedrock beneath. If ECAs are the surface expression of the storage and periodic drainage of pockets of water at the bottom of the ice sheet, they may represent an important control on ice sheet flow. In order to model the AIS, and any possible future change in flow brought about by climate change, we must understand the current basal environment of the AIS. This project will help scientists understand what generates these ECAs. The topography at the bottom of the ice sheet will be determined from ice-penetrating radar. If ECAs represent water pockets, extensive areas of flat, bright radar returns would be expected. In order to prove that there is considerable (decimetre to metre) thickness of water beneath any bright reflectors, seismic surveys will be used to tell us if there is water between the ice and underlying sediment beneath the ECAs. Radar and seismic surveys will be undertaken in 2008 and 2009, allowing change in the system to be mapped between the two surveys. If considerable water depths are not identified, the radar and seismic work should provide insights into the basal environment responsible for the generation of ECAs, most likely reflecting rapid changes in sedimentary landforms beneath the ice stream. The project will be conducted in collaboration with Dr. Tulaczyk (University of California) and Dr. Joughin (University of Washington). They plan to carry out fieldwork over the ECAs on the Binschadler Ice Sheet during 2007, 2008 and 2009. This fieldwork will involve setting up 10 long-term global positioning systems (GPS) over the ECAs, recording elevation change from 2007-2009. Field GPS surveys will also be conducted. This field data will be used along with satellite data to investigate change in ECAs and to improve models of ice flow in the region of the ECAs. Dr. Tulaczyk and Dr. Joughin have recently submitted a National Science Foundation (NSF) proposal to support the GPS and satellite work, including logistic support for three field seasons. Logistic support for this project will be supported through the NSF proposal. This NERC proposal asks for funding to allow the Principle Investigator to travel to Christchurch, New Zealand to join the US field party in 2008 and 2009. As such, this small grant represents incredible value for money for NERC science, as the core of the fieldwork budget will be supported through the international collaboration. This is a small, discrete project. Both radar and seismic surveys will be exploratory, as time constraints on field logistics will allow no more than 5 days of radar data and 6 days of seismic data to be collected during each field season. If successful, this project will provide proof-of-concept for future, more extensive radar and seismic investigations of the basal environment of ECAs on the Binschadler Ice Stream, other Siple Coast Ice Sheet systems in West Antarctica and the Dome C area of East Antarctica.