ANtarctic Grounding LInes from Cryosat (ANGeLIC)

The grounding line of the Antarctic Ice Sheet is the point at which ice leaves the continent and enters the ocean and contributes to sea level. It is where the ocean has its greatest influence on inland flow through bottom melting of floating ice shelves. It is, in fact, a zone (the Grounding Zone) where tidal motion, basal melting and ice dynamics are all key controls on its structure. The GZ is a dynamic feature of the ice sheet and changes in its location and structure may indicate the development of an instability in ice flow or a change in ice motion that will impact sea level and the future evolution of the ice sheet. Identifying and monitoring the evolution of the GZ is important, therefore, for providing i) an early warning of changes in state of the inland ice, ii) as an input into numerical models of ice sheet flow and iii) for measuring the flux of ice leaving the ice sheet.

The ice thickness at the grounding line is an essential variable for determining the flux of ice leaving the ice sheet based on observations of ice velocity. To date, there has been no satisfactory way to investigate the evolution of the GZ for the whole of Antarctica. The aim of this project is to achieve this goal using a novel approach applied to CryoSat 2 data. This satellite was launched in 2010 and has a unique instrument on board called the SIRAL, which provides, for the first time, the ability to resolve at high temporal and spatial resolution the detailed structure of the GZ. Proof of concept analyses indicate its huge potential for this but work is required to i) improve and verify the accuracy of the CryoSat 2 data and ii) fully develop the methods for studying the GZ. Once this is achieved, we intend to monitor the evolution of the GZ over at least a seven year period and hopefully extending this further into the future using the same methods. In the process, we will also address an outstanding issue related to the accuracy of the ice thickness estimates derived from surface elevation in the GZ and greatly improve the accuracy of ice thickness estimates over the freely floating shelves that fringe almost the entire coastline of Antarctica.

There are four broad categories of user groups who will benefit from the results and activities of the project in addition to scientists working directly on ice sheets and sea level rise. These are i) climate scientists, ii) the climate change policy community, iii) the general public, (including schools and teachers) and iv) Earth Observation and CryoSat data users.

i) Climate scientists (outside of the field of research). This includes, for example, the Earth System modelling community who are attempting to embed realistic ice sheet evolution into AOGCMs. Grounding line migration is a key component in this work. They will benefit from this project by having observational evidence for GZ dynamics, which can be used to calibrate or validate their model response. Some groups are even considering a data assimilation approach for key processes.

ii) Policy community. We have direct links with the following organizations who have benefited from previous related research and who will benefit from this work. The list below is not meant to be exhaustive but to illustrate the type of beneficiary in this category with an indication of how they might benefit.
UK Met Office & DECC: coordinating the AVOID programme (a DECC/DEFRA funded project, http://www.avoid.uk.net/)
Public Interest Research Centre (http://www.pirc.info/) provides climate policy documents for the public and UNFCC.
Scientific Committee on Antarctic Research: coordinating role for Antarctic science.
UN Environment Programme: provides information about climate change and sea level rise to general public and educational establishments.
European Environment Agency: delivers policy information to the EC and member states.
Resources for the Future (www.rff.org) is a US-based think tank that provides briefing information to the US govt. See for example: http://www.rff.org/Events/Pages/Ice-Sheets-on-the-Move.aspx.

These and other organisations will benefit from this project through gaining an understanding of how, and to what extent, the Antarctic ice sheet is changing with time and the implications of these changes for prediction. We have in the past, and will continue to in the future, provide direct input to these groups via briefing notes, technical reports, workshops and public events and informal contacts. These channels have been used to inform the groups on the latest understanding and the state of the art regarding Antarctic ice sheet dynamics. We will provide regular updates during the project and the final Project Report and invite them to comment on the project website. Past experience indicates that this category of end user has greatly benefited from a strong interaction and involvement with the experts doing the work.

iii) The general public. Antarctic research has huge potential for capturing the public imagination and engaging students at both primary and secondary level in issues related to climate change, environmental policy, glaciology and polar processes. We know this from first hand experience. The PI currently undertakes talks to local schools and to Secondary School Geography teachers through the Princes Teaching Institute (http://www.princes-ti.org.uk/SummerSchool/) and will continue to do this for this project.

iv) Finally, as mentioned in the previous section, we are working closely with ESA to ensure that the CryoSat 2 validation work undertaken in the project is of most value and benefit to them and to the CryoSat-2 user community. The recently launched Antarctic Climate Change Initiative (CCI) coordinated by ESA provides a powerful mechanism to widen the reach and impact of the project beyond the standard academic beneficiaries (http://cci.esa.int/). The CCI aims to provide Essential Climate Variables required by the UNFCC for scientific and operational applications and users.