The role of Ice and Ocean Dynamics in Driving Change on Pine Island Glacier Ice Shelf

In this thesis I present new methods, observations, and model output analysis to improve our understanding of the stability of Pine Island Glacier ice shelf. In doing so, I further our understanding of ice-ocean processes across Antarctic ice shelves.

First, I develop a new method for using CryoSat-2 radar altimetry data to derive ice shelf basal melt rates at unprecedented spatial and temporal resolutions. Applied to Pine Island Glacier ice shelf, I use these data to quantify the asymmetry in melt rates within a basal channel, showing that melt near the grounding line can be over 50% greater on the Coriolis-favoured side of a channel than the other. By combining these data with ice-penetrating airborne radar data, I also show that Pine Island Glacier ice shelf inherits its primary basal channel distribution from upstream of the grounding-line.

Next, I present analysis of MITgcm ocean model output to investigate the relative role of ocean forcing and geometric changes on basal melt rates and implied mass loss of Pine Island Glacier ice shelf between 2011 and 2021. I show that ocean variability was the primary control on inter-annual variability of melt and implied mass loss during this period. However, geometric changes strongly influence the spatial distribution of melt and the melt within the shear margins. These results highlight the ongoing role of anthropogenic climate change on the future stability of Pine Island Glacier ice shelf.

Finally, I use high-resolution satellite data and ice sheet model output to investigate changes in the stress state and buttressing capacity of Pine Island Glacier ice shelf between 2015 and 2024. I show that a large portion of the ice shelf transitioned to a tensile regime following a large calving event in 2020, which also saw the detachment of Piglet Glacier and the removal of downstream isotropic points. However, analysis of model output data shows the ice shelf is still providing significant buttressing to the grounded ice. This buttressing is largely being supplied by its remaining shear margins and a second tributary glacier to its south. High-resolution elevation and SAR data show an increase in both main trunk and shear margin rifting, suggesting this current state might only be transient.