A study on Antarctic Subglacial Lake using Cryosat-2 Satellite Radar Altimeter

Abstract

The ice surface measurements from satellite altimeter have discovered numbers of subglacial lakes since the surface height above active subglacial lake varies in accordance with the water storage of lake beneath ice sheet. In this study, the Antarctic subglacial lakes are studied by the Cryosat-2 satellite radar altimeter, which is the most recently launched by European Space Agency. The high-resolution processing of SARin mode yielding the elevation change rate (=Δh/Δt) enables us to verify the specific 2-D boundary of lake and to detect even the small-scale unknown lakes. In particular, the regions called Kamb Ice Stream and Whillans Ice Stream are the main study region of this thesis. In these regions the three subglacial lakes are newly discovered and those are named as Kamb Trunk 1, Kamb Trunk 2 and Upper Engelhardt, respectively. Those findings allow us to verify many of the previously unknown subglacial environments of corresponding area. First, the fluctuations of water storage in the lake Kamb Trunk 1 and Kamb Trunk 2 can be used to estimate the flow type of subglacial water on the ice-bedrock interface. Second, near the grounding line of Kamb Ice Stream, it is also discovered a downward vertical displacement in triangle-shaped region. Since the occurrence time of this event is coincident with the activities of upstream subglacial lakes, it could be a good example how the supply of subglacial water could affect the downstream ice thickness variation. Lastly, the discovery of Upper Engelhard subglacial lake is also very important clues to reveal the subglacial water pathway around Whillans and Kamb Ice Stream. The flow path revealed from the behaviors of subglacial lakes is coincident well with the simulation results that have been presented in several recent studies.