Reconstructing millennial-scale ice sheet change in the western Amundsen Sea Embayment, Antarctica, using high-precision exposure dating.

Accurate prediction of when and how much sea level rise is likely to take place in the future is of great societal and economic importance if governments are to successfully plan for the future in a warming world. The West Antarctic Ice Sheet (WAIS), and particularly its Amundsen Sea sector, is key to such predictions because it has the potential to retreat very rapidly, perhaps over just a few centuries. We urgently need improvements to models that predict its future stability because the water locked inside it has the potential to make a major contribution (up to 1.2 metres) to global sea level rise. This would result in widespread damage to low-lying cities around the world, including major coastal and economic hubs in Europe, such as London.

Information about the past size and shape of ice sheets is essential for testing and refining predictive models. However, despite its importance for understanding future sea level rise, modelling efforts in the Amundsen Sea Embayment (ASE) of Antarctica are currently hindered by a lack of data on the history of the WAIS, particularly in the western ASE (we know the general pattern of retreat and thinning in the eastern ASE, although some of the details are not yet clear). The proposed project will produce a unique high-resolution record of ice sheet thinning over the past 20,000 years from the poorly-known western ASE.

We will use exciting innovations in the technique of surface exposure dating to determine small fluctuations in ice sheet thickness with greater precision than has previously been achieved in Antarctica. Information on the shape and size of the WAIS over the past 20,000 years is contained within rocks deposited on the surface of Antarctica as the ice sheet has retreated and thinned since that time. Surface exposure dating involves collecting such rocks and measuring the abundance of an isotope, 10Be, concentrated within their upper surfaces, which acts as a chemical signal for the length of time since the rock was last covered by ice. Because we plan to collect this information from a range of heights above today's ice surface in the western ASE, we will be able to tell how rapidly that part of WAIS has thinned, and when the thinning started and stopped. As well as establishing the history of this part of the WAIS, this approach will also give us insight into the significance of ice sheet changes recorded and widely publicised over the past decade. For example, are they simply the continuation of a long-term trend of thinning, or have they only started happening relatively recently and, if so, why? By comparing the retreat history of glaciers in the western and eastern parts of the ASE, we will also learn how different parts of the ASE are likely to respond to future environmental change.

An important part of our proposal will be to further develop our existing collaborations with modellers who use geological data to test and tune their ice sheet models. Our data will permit significant improvements in these models, ultimately contributing to more accurate prediction of future global sea level rise.

1 Who might benefit?

Academia:
- Scientists who have a role in producing global sea level predictions. This includes glaciologists who seek to simulate and predict the response of the Antarctic ice sheets to environmental change, and modellers who require data on past ice sheet history for model validation.
- Members of the Scientific Committee on Antarctic Research-Antarctic Climate Evolution community ice sheet reconstruction project.
- The NERC Accelerator Mass Spectrometry Facility at Scottish Universities Environmental Research Centre (SUERC), who will develop cutting-edge expertise in high-precision 10Be cosmogenic dating through transfer of knowledge from Lamont-Doherty Earth Observatory, USA.
- Researchers in the UK and overseas, who will be able to use the enhanced capability at SUERC for their environmental research.

Government:
-The Intergovernmental Panel on Climate Change (IPCC). A key goal of their next report is to deliver improved predictions of ice loss from the West Antarctic Ice Sheet over the next century.
- Governmental and non-governmental advisors (e.g. Dept. of Energy & Climate Change, UK Environment Agency), who monitor prediction of sea level change. They will use output from models constrained by our data.
- The UK Living With Environmental Change (LWEC) partnership. Its IceSheets programme aims "to establish improved histories of ice sheet change to provide context and constraint for future projections".

Society:
- The general public and school children, especially those who have not previously had the opportunity or desire to engage with Antarctic research.
- Young women, who are under-represented in physical science subjects at university.


2 How?

Academia:
- Glaciologists will have an improved understanding of how the West Antarctic Ice Sheet has responded to environmental change in the past, and modellers will be provided with a key dataset for use in their models.
- SUERC's expertise in high-precision 10Be dating will attract more world-class researchers to use the facility, and will facilitate substantial advances in environmental research which have not previously been possible in the UK.

Government:
- Our results will be published in the peer-reviewed literature, which the IPCC use as the primary basis for their work.
- Our data will help to validate models that are used for improving sea level predictions. Governments worldwide who need to develop appropriate strategies for coping with the consequences of rising sea level will obtain more accurate predictions as a result.
- Our results will feed directly into the objectives of the LWEC IceSheets programme, which aims to understand the risks of climate change.

Society:
- School children and members of the public will gain better understanding of the link between the West Antarctic Ice Sheet and future sea level rise, and an appreciation of living in Antarctica. This will be achieved through:
1) Development of an activity for explaining our research to primary-age children, in collaboration with the Scott Polar Research Institute, Cambridge. This will be presented in local primary schools, feeding into the Key Stage 2 curriculum.
2) Outreach activities at the Cambridge Science Festival.
3) A blog hosted during our field campaign, where members of the public of all ages and backgrounds can learn about the work, post comments, and interact with us on a daily basis.
4) A Planet Earth online podcast, which will discuss results from the project; this has the potential to reach a wide-ranging audience from members of the public to government departments.
- Johnson will be a role-model for girls and young women through her interactions with them at a science career event and in her ongoing work as a Nuffield Science Bursary mentor.
PI Johnson and Co-I Roberts will use their experience as STEM Ambassadors to promote understanding of the proposed research within these activities.