Assimilating novel geophysical datasets into ice-sheet models: Experiments at the margins and interior of West Antarctica

Abstract

This thesis uses novel remote-sensing datasets in conjunction with focused modeling efforts to contextualize present and past changes in the mechanical behavior of the West Antarctic Ice Sheet. In the second and third chapters of the thesis, we explore the controls for sliding beneath Thwaites Glacier using surface velocity and elevation time series and the first swath radar scans of the subglacial topography in the ice-sheet interior. Observations of surface velocity and surface elevation over the last 10 years reveal that a system of subglacial lakes on Thwaites Glacier filled and drained without substantially changing the traction of the glacier to the ice-sheet bed. From swath topography recovered near these lakes, we diagnose the relationship between unresolved topography and basal shear stress inferred from ice geometry and surface velocity. In the fourth chapter, we present data collected at Hercules Dome, where swath radar data reveal bedforms and landscapes consistent with a marine proximal glaciated alpine valley network. These bed features require faster flow speeds for formation than the speeds observed at Hercules Dome today and suggest Hercules Dome may have been a nucleation center for ice-sheet growth preceding glaciation. In Chapter 5, we move downstream of Hercules Dome to Conway Ridge (formerly Ridge A), which sits between the van der Veen and Mercer Ice Streams. Encoded in the layer stratigraphy at Conway Ridge are signals that suggest ice flow around Conway Ridge has slowed as the ice sheet and bed topography isostatically equilibrated. Much of this evidence is linked to buried crevasse patterns that constrain past surface strain rates. These past surface crevasse features motivated the investigation of modern surface features and the focus of the sixthchapter concerned with crevasse area change on Thwaites Glacier.