Dynamical control on the response of Pine Island Glacier

It is expected that sea-level rise will impact coastal communities worldwide over the coming decades to centuries. In the UK, the vulnerability of coastal communities and assets is best characterised in terms of the likely frequency of the over-topping of sea-defences. For example, when they were built, the sea-defences for the city of London (including the Thames Barrier) were designed to protect London from all except the 1-in-1000 year flood event. A rise of 50 cm in global sea level will reduce this level of protection to 1-100 years, and a rise of 100 cm would reduce it to 1-in-10 years.

Pine Island Glacier is one of five glaciers in West Antarctica that are currently contributing sea-level rise at a significant and accelerating rate. The portion currently affected by thinning contains sufficient ice to raise global sea-level by around 25 cm - its neighbours account for another 50 cm.

Given the rate of ice-loss and the potential implications for sea-defence planning there is a clear requirement to understand and predict the future of Pine Island Glacier and its neighbours. However, as highlighted by the Intergovernmental Panel on Climate Change (IPCC, 2007), understanding the way that dynamic changes are transmitted through the glaciers draining ice sheets is so poorly understood that the IPCC believed it was the least well understood, and potentially the largest, contribution to sea-level rise in the coming century.

ISTAR-C will directly address this lack of knowledge, by seeking to understand the processes that are responsible for transmitting the effect of thinning of the floating ice shelf, upstream such that thinning can now be seen on much of the trunk and tributaries of Pine Island Glacier.

ISTAR-C will also use the most up-to-date methods available to measure the properties (rock-type and water-content) of the bed beneath several locations on Pine Island Glacier to determine their influence on the propagation of thinning. We will test the hypothesis that it is these bed conditions that are responsible for the fact that the tributaries of Pine Island Glacier appear to be thinning at different rates. Testing this hypothesis will give us a much better understanding on which to predict the future magnitudes of ice-thinning rates for the glacier.

To achieve these objectives we will collect data from Pine Island Glacier during two field seasons. These will include precise measurement of variations in ice-flow from the ice-shelf up the glacier and into its tributaries. We will image the bed of the glacier using radar and seismic techniques, and use satellite remote sensing to measure the changing configuration of the glacier in areas that cannot be accessed on the ground. We will use the data we have collected to drive and verify a set of computer simulations of the dynamics of Pine Island Glacier. Each of these will test a particular aspect of the glacier flow, and allow us to test our current knowledge and hypotheses against real data. The models that emerge from the exercise will be demonstrably more reliable in simulating past changes on the glacier, and thus have reduced uncertainty in predicting the future evolution of such changes, and the consequential contribution to sea-level rise.

Overall, this programme will deliver significant improvements in understanding of how glaciers in general interact with their beds, and very specific lessons about one of the most rapidly-changing and significant glaciers on the planet, Pine Island Glacier.

The research undertaken in iSTAR-C will improve understanding of the causes of rapid change observed in parts of the West Antarctic ice sheet (WAIS) and how these may contribute to sea-level rise in future. While production of sea-level rise projections is not included within iSTAR-C, this programme will deliver understanding that underpins such projections, and will reduce uncertainty, and increase confidence, in those projections. Thus, the most significant economic and societal impacts of iSTAR-C will be realised as the science outcomes from iSTAR-C are taken up by beneficiaries beyond the immediate colleagues of the Co-Is; there are researchers and non-research scientists and engineers, who are directly undertaking sea-level rise projections.

Within this group we identify several key beneficiaries who will be users of iSTAR-C outcomes.

1. Academic researchers: (e.g., Proudman Oceanographic Institute, UK Climate Impacts Programme) who have a role in producing local, regional and global sea-level projections, and delivering to users.

2. Intergovernmental Panel on Climate Change (IPCC). The IPCC is by far the most influential group synthesising and delivering sea-level rise projections to policy-makers.

3. Governmental and non-governmental advisors. (E.g.; Dept. of Energy and Climate Change, UK Environment Agency) closely monitor science regarding sea-level protection and are influential in bringing science in the agenda of policy-makers.
Engaging with these and similar groups will maximise the value of iSTAR-C.

In an even wider frame, iSTAR-C and projects like it, which seek to improve the underlying science on which we base our projections of future state of the planet, should play an important role in re-establishing public confidence in science. The nature of the iSTAR-C programme, which focuses on an exciting work in an inspiring area, and on current and unarguable changes in the Earth System, will draw the attention of many people not normally turned on by science. This will give iSTAR-C a great opportunity to engage with individuals and we will not squander this opportunity. We will seek to present and frame iSTAR-C outcomes without policy-prescriptive implications, but in a spirit of informing rational evidence-based debate. We will seek a dialogue with groups and individuals who share this goal.