Investigating Antarctic ice sheet subglacial processes beneath the Whillans Ice Plain, West Antarctica, using satellite altimetry and GPS
The Antarctic ice sheet has an extensive basal water system that lubricates the ice-bed interface and enables the fast flow of ice streams and outlet glaciers, which account for a majority of Antarctic ice discharge to the ocean. In the past decade, observational evidence has suggested that the subglacial hydrology of Antarctica can be non-steady, changing on sub-decadal timescales, but the effect of dynamic hydrology on ice flow remains uncertain. The Whillans Ice Plain (WIP), at the confluence of the Whillans and Mercer ice streams, West Antarctica, has been studied for over 50 years and has been identified as a region with extensive active subglacial hydrology. In this dissertation, we develop and implement methods using a combination of ground-based Global Positioning System (GPS) data and satellite-based radar and laser altimetry to observe the surface expression of water movement beneath WIP, quantify the dynamic ice-flow response to an evolving basal water system, and investigate processes driven by the interaction of WIP with ocean tides that may impact subglacial water flow near the grounding line. We find that the coupled subglacial-ice stream system can respond rapidly to basal perturbations on sub-annual timescales and in ways that are not captured by simple models. We demonstrate that the location where subglacial water enters the ocean is a complex interface that requires significant improvement to our measurement precision to better understand important time-varying processes. We also apply our method for observing dynamic ice-surface height changes to the inventory of known subglacial lakes in Antarctica to extend our observational record and assess variability of the subglacial hydrologic system in different physical settings. Through this continent-wide analysis of subglacial lakes, we suggest that our current knowledge of the characteristic spatial and temporal scales of hydrologic variability is still limited by our observational capacity. We conclude by proposing future studies that would address knowledge gaps currently preventing the inclusion of an evolving basal water system into large-scale predictive models of ice-sheet flow.