Subglacial topography and landscape evolution from radio-echo sounding data in the Evans-Rutford Region, southern Antarctic Peninsula.

Abstract

Knowledge of the subglacial bedrock topography of the Antarctic ice sheet is important for understanding modern and past ice flow as well as the present basal conditions. Inferring landscape evolution from the subglacial geomorphology can also provide insight into ice sheet interactions with other processes such as tectonics. This thesis utilises newly released radio-echo sounding data from the British Antarctic Survey GRADES-IMAGE radar survey to geomorphologically interpret the bed topography in the Evans-Rutford Region of Antarctica. The GRADES-IMAGE survey is a legacy radar survey that has not yet been examined in detail in terms of subglacial bed topography. In the work presented here, a new high-resolution Digital Elevation Model of the region has been generated, and the resulting subglacial landscape was mapped to delineate distinct geomorphological features. Hypsometric (area-elevation) analysis was carried out to characterise the landscape morphology, and a flexural isostatic rebounding model was applied in order to help consider the age and evolution of the pre-glacial landscape. The main finding from analysis of the subglacial features is the identification of ten flat plateau surfaces distributed throughout the study region. These plateaux sit under cold-based ice between deep incised glacial troughs, some of which have potential tectonic controls. Two populations of plateaux have been identified as potentially coherent pre-glacial surfaces. Three hypotheses are presented for the evolution of the regional landscape: passive margin evolution associated with the breakup of the Gondwana supercontinent, or an extensive planation surface that may have been uplifted either in association with the West Antarctic Rift System, or cessation of subduction at the base of the Antarctic Peninsula. Regardless of the process of formation, glacial erosion of the surrounding troughs likely coincided with the inception of the West Antarctic Ice Sheet, with the ice flow and erosion patterns topographically controlled by the regional tectonics.