Investigating topographic controls on Antarctic Ice Sheet flow and retreat

The Antarctic Ice Sheet has the potential to contribute over a meter of sea level rise by the end of the century. Despite recent advancements in direct observations and understanding, key processes at the ice-bed interface—crucial for governing its complex ice dynamics—remain unconstrained. The work presented here leverages high-resolution bathymetry from deglaciated landscapes to gain insight into local- and subglacial-scale processes governing ice sheet dynamics. To quantify the impact of subglacial bed roughness on ice flow, Chapter 2 compares different methods to assess their suitability. Results demonstrate that bed roughness measurements are significantly influenced by orientation, scale, and methodology, highlighting the importance of standardized approaches. The standard deviation method emerged as a robust tool for characterizing bed roughness, particularly in the context of paleo-ice stream bed. However, limitations imposed by low-resolution topography data, especially beneath contemporary Thwaites Glacier, West Antarctica, underscore the need for improved data acquisition. To enhance the understanding of subglacial landform evolution and its implications for ice dynamics, Chapter 3 applies an automated landform identification method to high-resolution bathymetry in the Western Ross Sea. This approach revealed a substantial increase in the number of identified landforms compared to traditional visual methods, providing new insights into landform morphology and distribution. Statistical analyses demonstrated a strong correlation between local bed slope and landform morphometrics, with steeper reverse slopes inhibiting vertical growth and influencing landform amplitude and width. Moreover, metrics suggest that ice sheet retreat has exhibited both steady and episodic phases, influenced by long-term climate variability. To explore the mechanisms controlling the formation and geometry of grounding zone wedges (GZWs), landforms formed at the terminus of marine-terminating glaciers and ice streams, a numerical model of sediment accumulation at the grounding line is used to investigate controls such as local bed slope, the depth of the deformable layer, and stoss angle. While the model successfully reproduced the asymmetry shape of GZWs and shows sediment flux to be a key control in the dimensions of GZWs, further research should incorporate additional climate forcings and local environmental variables to improve model performance. Collectively, this research advances our understanding of the critical role of small-scale topography in controlling AIS flow and retreat. By improving the characterization of bed toughness, identifying subglacial landforms, and modeling glacier-bed interactions, this dissertation contributes to a more comprehensive picture of ice sheet dynamics and its findings can refine and improve ice sheet models for better predictions of future sea level rise.