Measuring and Modelling glacier retreat in the Amundsen Sea, Antarctica (iStar project)

Informal inquiries should be directed to Andy Shepherd ([Email Address Removed])
Full project description: http://www.nercdtp.leeds.ac.uk/projects/index.php?id=135

Changes in the mass of the polar ice sheets are of considerable societal importance because they reflect changes in climatic conditions and because they affect global sea level rise. Today, the largest signal of ice sheet imbalance is occurring in the Amundsen Sea sector of West Antarctica, where glacier retreat, acceleration, and thinning are widespread as a consequence of oceanic forcing. This project will focus on the Thwaites and Smith glacier systems in the Amundsen Sea. This PhD will aim to:
- develop a suite of Earth Observation measurements for the Thwaites and Smith glacier
- use the latest advances in ice sheet modelling to understand the dynamics and evolution of these glaciers

1. Background
The West Antarctic Ice Sheet contains enough ice to raise sea level by over 3 metres, and the Amundsen Sea sector is susceptible to accelerated retreat due to bedrock topography that lies well below sea level, deepening inland, without a substantial floating ice shelf barrier. Satellite observations show that glaciers draining this sector are retreating, thinning, accelerating, and losing mass. Observations of ice shelf thinning in the face of increased glacier discharge and a numerical simulation of glacier response to external forcing suggests that the surrounding ocean is the source of this imbalance.

The Pine Island, Thwaites, and Smith glaciers are major tributaries of the Amundsen Sea sector, and the Pine Island glacier has retreated by up to 25 km between 1992 and 2009. Although satellite observations show that the termini of the Thwaites and Smith glaciers have also thinned rapidly, there are far fewer observations of their hinge-line positions, and it is not clear to what extent either glacier has experienced similar retreat. The evolution of the Thwaites and Smith Glacier systems has yet to be simulated, primarily due to the absence of detailed constraints on the recent perturbations at their grounding lines.

2. Method
This PhD will generate new satellite observations of the Thwaites and Smith glacier retreat to complement those developed at the Pine Island glacier within the iSTAR project. This will be achieved by combining a range of techniques. First, hinge line positions will be mapped with fine spatial resolution using interferometric synthetic aperture radar (InSAR). Next, to obtain finer temporal resolution, two separate satellite altimetry techniques will be combined. Changes in the thickness of grounded and floating ice will be determined using altimeter measurements at orbit crossing points, applying a buoyancy correction over floating ice. This will be used to calculate rates of grounding line migration. In addition, the technique of repeat-track altimetry will be used to map the limit of tidal flexure. This work will provide the first detailed and comprehensive survey of AS glacier grounding line retreat.

The second part of the PhD will aim to understand the processes that lead to the recent changes observed in the AS sector using the BISICLES ice sheet model. BISICLES is based on adaptive mesh refinement (AMR), a technology which provides the fine resolution required to model grounding-line migration accurately, while being efficient and quick to run. Based on the information provided by the satellite observations, the BISICLES model will be used to test different hypotheses on the cause of observed changes in the AS sector.


3. Training
This project will provide the successful PhD candidate with highly valued and sought-after skills in numerical modelling and remote observation of ice and a deep understanding of glaciological processes. This will equip the student with the necessary expertise to become the next generation of glaciologist, ready to carry out their own programme of innovative scientific research.
The student will benefit from working within the dynamic and multidisciplinary Physical Climate Change research groups; as well as from collaborating with researchers in the iSTAR project. There will be opportunities to present results at major, international conferences, e.g. AGU (San Francisco), EGU (Vienna) and attend residential summer-schools (e.g. in Italy, USA, UK) and in-house workshops and courses.