East Antarctic radar-derived englacial stratigraphy and structure : past and present glaciological implications

Abstract

The East Antarctic Ice Sheet (EAIS) is likely to play a major role in contributing to future global sea-level rise. Satellite observations and numerical modelling demonstrate that regions of the EAIS may become increasingly vulnerable to future warming. Observational evidence of ice-flow changes and long-term mass balance records are vital to understand how the ice sheet evolved and consequently, how it may change in the future. This thesis presents a comprehensive study of: (i) the internal structure of disrupted englacial stratigraphy throughout Lambert Glacier, revealing ice-flow direction stability during the Holocene. The analysis provides a novel methodology using the internal stratigraphy, derived from radio-echo sounding (RES) data, to interpreting and understand historic ice flow patterns and shear margin positions. This method could be directly applied to understanding ice streams across East Antarctica; (ii) the age-depth relationship from Dome A to South Pole by tracing three internal reflection horizons dated to 38.2 ka, 90.4 ka and 161.9 ka. The spatial geometry of these layers elucidates past ice-flow dynamics and suggests two locations (upper Byrd Glacier catchment and the Gamburtsev Subglacial Mountains) where old ice may be present; (iii) complex internal stratigraphy, the loss of radar reflection strength and clear birefringence patterns within RES data are persistent across Academy Glacier. These features can obscure automated analysis of RES data, as data is lost when internal layers dip as a result variations in bed topography and from variable ice flow trajectories. Yet these features are often overlooked, not considered in ice-sheet models, but may reflect past and present ice dynamics, as demonstrated in this thesis for Academy Glacier. The internal structure and stratigraphy of the EAIS, imaged using RES, provides critical insights into the past and present dynamics of two ice flow catchments, that combined drain ~10% of the EAIS. Using the internal stratigraphy from RES, ice core records, combined with 1D ice-flow models, the Lambert Glacier and Academy Glacier catchments are stratigraphically connected, resulting in a new dated stratigraphy across central East Antarctica. The EAIS-wide investigation of englacial structure and stratigraphy presented here has improved our understanding of its configuration and stability, providing a foundation for understanding East Antarctica’s future role in global sea level change.